WHITE PAPER SYNCHRO-SYM Technologies: Brushless, Symmetrically

Best Electric Machine White Paper

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WHITE PAPER

SYNCHRO-SYM Technologies:

Brushless,Symmetrically Stable,

Wound-Rotor Doubly-Fed, Synchronous,

Electric Motor or Generator System And

Vertical Integration Technologies

Best Electric Machine (BEM)

[email protected] “If cost, efficiency, reliability, power density and torque density are the deciding factors, basic physics shows no electric motor or generator system competes with SYNCHRO-SYM!” WHY?

1. Only electric motor or generator with brushless, symmetrically stable, real-time control that eliminates loss of synchronism regardless of speed or perturbation;

2. Only electric motor or generator with both rotor and stator real-estate actively sharing in the energy conversion process for highest power density, lowest cost, and highest efficiency;

3. Only electric motor or generator with contiguous synchronous control by controlling half (or less) of the total power for highest power density, lowest cost, and highest efficiency;

4. Only electric motor or generator with a symmetrical dual-ported transformer topology that inhibits magnetic saturation for significantly higher torque and power density potential;

5. Only electric machine or generator with controllable “constant-torque” range between absolute zero speeds to twice synchronous speed for a given torque and frequency of excitation (with higher speeds enter the constant-horsepower range).

“SYNCHRO-SYM shows twice the power density with higher efficiency but one-quarter the cost of state-of-art neodymium permanent magnet motors and generators!” “By simply replacing the rotor assembly and electronic controller of virtually any electric machine system, such as the rare earth permanent magnet (PM) assembly of PM electric machine system, with the wound-rotor assembly and Real-Time Controller of SYNCHRO-SYM, the result is SYNCHRO-SYM with twice the power and at least half the cost as the original electric machine system and significantly higher peak torque density per nominal frame size under the same frequency and voltage of excitation.”



TABLE OF CONTENT 1. Glossary of Terms....................................................................................................... 3 2. Introduction................................................................................................................. 3

a. Electric Motor or Generator (EMS) 101................................................................. 6 3. BEM SYNCHRO-SYM.............................................................................................. 8

b. BEM SYNCHRO-SYM Background ..................................................................... 8 c. BEM SYNCHRO-SYM Achievements.................................................................. 9 d. Conventional EMS Details ................................................................................... 10 e. BEM SYNCHRO-SYM Working Details ............................................................ 12 f. BEM SYNCHRO-SYM Unique Attractive Attributes ......................................... 14 g. BEM SYNCHRO-SYM Perceived Concerns:...................................................... 18

4. Rotor Excitation Generator (REG) ........................................................................... 20 a. BEM Rotor Excitation Generator (REG).............................................................. 20 b. Conventional EMS Electronic Controllers ........................................................... 20 c. BEM REG Operating Details................................................................................ 21 d. REG versus Conventional EMS Controllers......................................................... 22 e. REG Assessment................................................................................................... 23 f. Effective Power Switch Utilization For AC and DC Control............................... 24 g. Effective Power Switch Loss Factor..................................................................... 27

5. BEM Power Stacking and Smart Manufacturing Tool Technologies ...................... 28 a. BEM Axial Flux Form-Factor .............................................................................. 28 b. BEM Power Stacking Technology........................................................................ 28 c. BEM Flexible Axial-Flux Smart Manufacturing Tool ......................................... 28

6. BEM Short Range Electrical Power Distribution Bus or (EPDB)............................ 29 a. Conventional High Performance DC EPDB......................................................... 30 b. BEM Advanced EPDB Strategy ........................................................................... 31 c. BEM Advanced EPDB (or A-EPDB) ................................................................... 31 d. BEM Advanced EPDB Conceptual Overview ..................................................... 33

7. BEM Proposal and Associated Risks........................................................................ 36 a. BEM Value Added................................................................................................ 36 b. BEM Technology Assessment.............................................................................. 36

8. APPENDIX I (EMS Design Constraints) ................................................................. 37 9. APPENDIX II (DC and AC Power Transfer)........................................................... 39 10. APPENDIX III (Bibliography of Professional Publications) ............................... 46

a. Power Density Attribute of Wound-Rotor Doubly-Fed EMS .............................. 47 b. Torque Density Attribute of Wound-Rotor Doubly-Fed EMS............................. 47 c. Electronic Controller Attributes of Wound-Rotor Doubly-Fed EMS................... 47 d. Slip-ring Limitation of Conventional Wound-Rotor Doubly-Fed EMS............... 47 e. Stability Limitation of Conventional Wound-Rotor Doubly-Fed EMS ............... 47 f. Neodymium-Dysprosium Permanent Magnet Cartel............................................ 48 g. Motor Efficiency Deadlines For European Union ................................................ 48 h. Electric Machine Core Loss.................................................................................. 48 i. Comparable Emerging Technologies.................................................................... 48



1. Glossary of Terms AC Alternating Current;A-EPDB Patent pending Advanced EPDB; BEM Best Electric Machine (a.k.a., Engineering Devices Inc.); C-WRDF-EMS Conventional Wound-Rotor Doubly-Fed Induction Electric Machine

System with known instability and multiphase slip-ring assembly; DC Direct Current;EPDB Electrical Power Distribution Bus EMS Electric Machine System, which is an electric motor or generator

with electronic controller; EV Electric Road Vehicle, Electric Ships, or Propulsion Systems; FOC Any Derivative of Field Oriented Control, which is today’s state of

art control method; MMF Magneto-Motive-Force or the product of winding current and

winding-turn count; MPVF-AC Multiphase variable frequency AC; PDF-HFT Position-Dependent Flux High Frequency Transformer or the

electromagnetic computer of the REG. PEBB Power Electronic Build Block PM Permanent Magnet;PST Patent pending Power Stacking Technology that accommodates

stacking lower rated EMS to achieve higher power in the same diameter package without compromising field service and cooling;

REG Patent pending Rotor Excitation Generator with BRTC of SYNCHRO-SYM;

RMS Root Mean Square or average power. BRTC Brushless and Stable Real Time Control provides automatic and

instantaneous motion-based excitation. SCMT Patent pending Smart Core Manufacturing Tool for just-in-time

manufacture of axial flux cores with universal frame assemblies; SYNCHRO-SYM Patent Pending (and only) brushless and symmetrically stable

wound-rotor doubly-fed synchronous EMS; WRDF Wound-Rotor Doubly-Fed electric machine core topology without

slip-rings or control. 2. Introduction To meet the goals of reliability, modularity, scalability, commonality, and easy field maintenance for electric motors and generators, Best Electric Machine (BEM) is offering at least four symbiotic technologies referred to as SYNCHRO-SYM Technologies, which are patented or patent pending inventions. SYNCHRO-SYM Technologies provide vertical integration to SYNCHRO-SYM or a transformational electric motor or generator



system with the highest efficiency, highest power density, and highest torque density but at the lowest cost. SYNCHRO-SYM Technologies: 1. SYNCHRO-SYM:

The “only” brushless, symmetrically stable, and “synchronous” wound-rotor doubly-fed electric motor or generator system (i.e., electric machine system or EMS);

2. PST or Power Stacking Technology; 3. SCMT or Smart Core Manufacturing Tool Technology; 4. A-EPDB or Advanced Electric Power Distribution Bus Technology. Electric propulsion and generation technology are electric motor and generator systems, commonly referred to as electric machine systems (EMS). With SYNCHRO-SYM as the exception, all other EMS are sub-categorized as either: 1) the conventional or superconductor field-wound (i.e., DC electromagnet) singly-fed synchronous EMS; 2) the permanent magnet (PM) singly-fed synchronous EMS; 3) the singly-fed synchronous reluctance EMS; 4) the self-commutated DC or universal EMS; or 5) the advanced transformer EMS topologies that rely on motion-based asynchronous (i.e., induction) principles, such as all singly-fed and doubly-fed “Induction” or Reluctance EMS technologies, which include the conventional wound-rotor doubly-fed induction electric machine system (C-WRDF-EMS). High performance EMS incorporate electronic control but in addition, a) the high performance PM-EMS technologies comprise delicate and expensive PM materials (and manufacturing) virtually indigenous to a single country of origin; b) the field-wound and superconductor EMS technologies comprise slip-rings or worse exotic superconductors with complex ancillary cryogenic apparatus and hydraulics; c) the universal EMS comprise an brush-electromechanical commutator; d) the advanced transformer singly-fed “Induction” EMS technologies comprise the bulk and inefficiency of extra winding sets for motion-based induction, and e) the advanced transformer doubly-fed “Induction” EMS technologies comprise the bulk and inefficiency of a multiphase slip-ring assembly or extra winding sets with a special rotor assembly for focusing unlike pole-pair motion-based induction to manage discontinuous doubly-fed power over a limited or discontinuous speed range. As the only truly symmetrical dual-ported transformer topology (i.e., dual armature) stabilized by real-time control that does not rely on electromechanical contacts (i.e., slip-ring assembly) or motion-based induction, only the rotor real-estate of SYNCHRO-SYM actively participates in the energy conversion process at any speed to offer the most optimized magnetic core topology available. As experts theorized with true wound-rotor synchronous doubly-fed principles, SYNCHRO-SYM provides nearly half the electrical loss (i.e., highest efficiency), half the cost, twice the power density, and at least eight times the peak torque density of any other EMS with off-the-shelf components and without strategic materials or exotic technologies, such as PM or superconductor “field windings.” [Note: It is technically impractical to use superconductors in an active winding set (or armature) but the active winding set is where virtually all EMS electrical



loss occurs. As a result, superconductors provide high air-gap flux density to lower the electrical loss of the active winding resulting from torque MMF, which is not the result of superconductors providing a zero loss EMS.] Likewise, SYNCHRO-SYM can leverage virtually any EMS material, technology, or method available or in research and development (R+D). By simplifying the proprietary electronic controller of SYNCHRO-SYM, an advanced electrical power distribution technology (A-EPDB) is conveniently realized, which provides connection between doubly-fed EMS technology, such as SYNCHRO-SYM in particular, and non-compatible power mediums, such as DC, batteries, etc. SYNCHRO-SYM is complemented with two vertical integration technologies: 1) Power Stacking Technology (PST), which provides modularity, scalability, and commonality, reduced component inventory, improved cooling, and easy field service, and 2) Smart Core Manufacturing Tool Technology (SCMT), which provides a precision, low cost, just-in-time manufacturing station for fabricating universal axial-flux EMS cores with integral frame structure from unfinished but readily available materials and stock. With an overabundance of subsidized research investment, the rather recent development of the neodymium-dysprosium PM-EMS was unhindered by past industry practices of standard frame sizes and form-factors that otherwise continue to constrain the optimization of other EMS with the same asymmetrical circuit topology, such as the Induction EMS. Now, the PM-EMS is blindly considered the most efficient and highest power density EMS technology of today. But with the escalating global demand for cartel-controlled neodymium and dysprosium materials predicted to outstrip the output of their especially environmentally unfriendly mining operations worldwide, household name motor companies are already seeking conventional alternatives to the singly-fed PM-EMS, such as the singly-fed or doubly-fed Reluctance EMS, the singly-fed Field-wound Synchronous EMS, the singly-fed or doubly-fed Induction EMS, and the even rarer singly-fed Samarian-cobalt PM-EMS, which are all showing similar continuous power density and system efficiency as experts expected but previously perceived to be peculiar to the neodymium-dysprosium PM-EMS. With electric propulsion technology now leaning towards advanced singly-fed EMS technology, such as the singly-fed induction EMS or the field-wound (i.e., electromagnet) synchronous EMS, the brushless, synchronous, and symmetrically stable wound-rotor doubly-fed SYNCHRO-SYM is surely a recognizable improvement to those in the know with higher peak torque potential, higher efficiency, higher power density, lower cost, and better durability but without exotic materials or technologies. Complemented with the patent pending Power Stacking Technology and the Smart Manufacturing Tooling of BEM for axial flux form-factor core and integral frame, SYNCHRO-SYM also leverages the integrated rotor electronics, better cooling, and tighter air-gap tolerance, which are advertised to be notable advantages of commercially available PM-EMS with axial-flux technology. IMPORTANT NOTICE: As the “only” brushless, stable and synchronous solution, please recognize SYNCHRO-SYM should never be confused with the conventional wound-rotor doubly-fed induction electric machine (C-WRDF-EMS), which is fading into antiquity because continuing institutional research has never successfully solved the known issues of instability,



multiphase slip-ring assemblies, or reliance on motion-based induction. No wonder industry misconceptions range from the impossible to the unsubstantiated existence of a brushless, stable, wound-rotor doubly-fed synchronous electric machine that miraculously does not predate or contend with the SYNCHRO-SYM patents. Before inadvertently accepting the fallible information commonly experienced in the electric machine industry, particularly when acquiring advice from electric machine experts with conflict of interest agendas, such as funded competitive electric machine research or affiliation with the offshore permanent magnet cartel, BEM graciously asks the evaluator of this white paper to contact the holder of patents and sole keeper of SYNCHRO-SYM knowledge base at [email protected] for fair opportunity to clarify any misconceptions.

a. Electric Motor or Generator (EMS) 101 An EMS converts electrical energy to mechanical energy or vice-versa with all rotating magnetic EMS having four basic components: 1) a rotor body with a rotating magnetic field; 2) a stator body with another rotating magnetic field; 3) a mechanical structure and bearing assembly for articulated containment and structural integrity; and 4) an electronic controller for practical variable speed operation. The rotor and stator rotating magnetic fields must be synchronized for average torque production with rotary and linear electric machines following the same principles of operation. All EMS follow the same design relationships (see APPENDIX I (EMS Design Constraints) on page 37), which dispels the marketing gimmickry prevalent in the industry. A rotating magnetic field, which actively participates in the energy or power conversion process, is produced by a multiphase winding set (or armature) that supports bi-directional flow of multiphase alternating current (AC) electrical power and as a result, contributes to the power production rating of the EMS (i.e., working power). In contrast, a rotating magnetic field, which passively participates in the energy conversion process, is produced by AC or direct current (DC) windings, permanent magnets, or salient steel poles (i.e., reluctance) that are without bi-directional AC electrical power flow and only establish the magnetic field by rotor movement and as a result, do not contribute to power production but only dissipate power as a result of eddy, hysteresis, windage, stray, etc. loss or reactive power. Without a rotating magnetic field, the electronic controller component and the mechanical structure and bearing assembly component are truly passive components that do not contribute directly to electromechanical conversion but only add similar cost, size, and inefficiency (i.e., electrical loss) per KW of component rating between EMS types with the same design optimization available to all EMS types. Likewise, a passive rotor or stator body does not contribute to power rating but only adds cost, size, and inefficiency per KW of component rating in accordance to the EMS type, such as the induction, permanent magnet, electromagnet, or reluctance electric machine. In contrast, an active rotor body or stator body contributes to power rating of the EMS with similar cost, size, and inefficiency per KW of component rating with the same design optimization that is available to all EMS types. With efficiency and cost always



normalized to power production rating, passive components are costly, inefficient, and consume real estate without power production. Continuous torque (or torque density) per KW of power rating of an EMS depends on how much air-gap magnetic flux density and current can be squeezed through the magnetic core and into the armature(s), respectively, while continuously operating at a given AC frequency and power rating. With perhaps the Superconductor EMS as the exception, all EMS, including permanent magnet EMS, are designed to the same flux saturation constraints of the magnetic steel core for air-gap flux density and to the same air-gap area, winding capacity, slots per pole-pair, pole-pairs, back-iron depth, etc. constraints for the same power rated armature. As a result, torque (or torque density) depends on the same mechanical optimization techniques for the armature(s), such as air-gap depth, electrical, and material science, with all equally rated EMS showing similar armature size, which effectively determines the overall EMS size. Continuous power rating of an EMS is the product of the continuous torque and the constant-torque speed range. With similar torque density between EMS, the constant-torque speed range determines the continuous power or power density between EMS. EMS cost, size, and efficiency per KW rating are calculated from the cost, size, and efficiency per KW rating of each of the four EMS components. An EMS that comprises both active rotor and stator bodies (i.e., dual armatures or doubly-fed), which is only provided by a true wound-rotor doubly-fed EMS, achieves twice the constant torque speed range for a given torque, voltage and excitation frequency with the cost, inefficiency and real estate of the rotor and stator armature bodies always providing additional working power for significant improvement in power rating and power density. In contrast, all other EMS have a stator armature body with similar cost, inefficiency, and real estate as a single armature body of the wound-rotor doubly-fed EMS but also include the inefficiencies and wasted cost and size of a passive induction, permanent magnet, electromagnet, or reluctance rotor body. Theoretically, only the true wound-rotor doubly-fed EMS shows half the volume per KW of rating, half the cost per KW of rating, and more efficiency than other EMS without considering the proportionally lower loss of its half rated electronic controller. Driven by the practical design of the armature, continuous torque density is virtually the same amongst all EMS optimized to a given specification. As a result, there are only three means of increasing continuous power density amongst EMS optimized to a given rating specification: 1. Actively utilize both the rotor and stator real estate as only SYNCHRO-SYM does,

which nearly doubles the power density by design; 2. Change the frequency of excitation design to respectively decrease the torque and

increase the speed, which is available to all EMS, including SYNCHRO-SYM; 3. Increasing air-gap flux density by futuristic superconductor field windings or by

improving magnetic saturation of the core materials. [SYNCHRO-SYM Technology brings superconductor EMS closer to practical reality.]



3. BEM SYNCHRO-SYM

b. BEM SYNCHRO-SYM Background Traditionally, there are two basic categories of electric motors or generators (i.e., electric machines): 1) the popular singly-fed electric machine with one independently excited multiphase AC winding set, such as the squirrel cage asynchronous (i.e., induction) electric machines, the reluctance synchronous electric machines, and the permanent magnet (or field wound) synchronous electric machines; and 2) the unusual doubly-fed induction electric machines with two independently excited multiphase AC winding sets (i.e., dual armature or doubly-fed), which is the maximum allowed without basic category duplication. Known as their constant torque speed ranges, a singly-fed electric machine only operates to synchronous speed for a given torque, voltage and frequency of excitation but in contrast, a doubly-fed electric machine operates to twice synchronous speed, which is tantamount to twice the power density. For practical variable speed operation, a true doubly-fed EMS must have a contiguous constant-torque speed range from zero to twice synchronous speed and with this understanding, slip-recovery wound-rotor induction EMS and field-winding synchronous EMS should never be considered doubly-fed, which is a common mistake. Despite years of global research and development by academic and industrial institutions, doubly-fed electric motor and generator systems have been kept from commercial success by known but unsolved limitations, such as: 1) instability (i.e., torque is a function of position and requires inventive instantaneous feedback control); 2) heavy reliance on motion-based asynchronous operating principles (i.e., speed-based induction shows at least an extra winding set of loss and is discontinuous at synchronous speed); or 3) a multiphase slip-ring assembly for articulated and independent electrical connection to the multiphase rotor winding set (i.e., slip-ring assemblies are inefficient, high maintenance, low reliability, poor current capacity, real-estate consuming, and extra cost). [The reader is encouraged to review APPENDIX II (DC and AC Power Transfer) on page 42.] Disregarding the unsolved limitations, the symmetrical electromagnetic relations of the conventional “wound-rotor” doubly-fed (WRDF) induction electric machine system (C-WRDF-EMS) describe the most optimal electromagnetic core topology available with uniquely theoretical attributes of half the electrical losses, half the cost, twice the power density, and factors higher peak torque for a given design rating than the closest EMS competitor, all of which were articulated by pioneering works of Drs. Albertson, Long, Novotny, and Schmitz from the engineering department of the University of Wisconsin and continually verified by decades of subsequent global research always attempting to find solutions to overcome the C-WRDF-EMS limitations. By conceding symmetry of the electromagnetic relations of the C-WRDF-EMS and the attractive attributes provided, the resulting asymmetrical (i.e., non-linear) electromagnetic relations become the academic study for all other EMS, including the popular singly-fed PM-EMS and Induction-EMS. Although non-linear relations greatly challenge all aspects of design, including thermal, magnetic, electric, mechanical, and etc., ironically, the asymmetrical EMS, such as the PM-EMS, is pushing the symmetrical and theoretically superior C-WRDF-EMS into antiquity clearly because of instability and the multiphase-slip-ring assembly that Novotny and Schmitz realized



could only be overcome with the inconceivable invention of brushless instantaneous (i.e., real time) control.

c. BEM SYNCHRO-SYM Achievements Defying decades of failures by industry and academia to find solutions, Best Electric Machine (BEM) continued with C-WRDF-EMS research to successfully develop and patent a brushless real-time control means and as a result, the “only” brushless and symmetrically stable wound-rotor doubly-fed “synchronous” EMS (or SYNCHRO-SYM). Never to be confused with the inferior C-WRDF-EMS, it is important to over emphasize the unique, transformational achievements of SYNCHRO-SYM:

- NO BRUSHES, SLIP-RINGS, or ELECTRO-MECHANICAL CONTACTS OF ANY KIND!

- SYMETRICALLY STABLE MOTORING AND GENERATING

MODES OF OPERATION AT ANY SPEED!

- FOLLOWS SYNCHRONOUS PRINCIPLES WITH NO DISCONTINUITY AND DOES NOT RELY ON MOTION-BASED INDUCTION FOR OPERATION (i.e., ACTIVE ROTOR REAL ESTATE)!

- CONTROLLABLE “CONSTANT-TORQUE” RANGE BETWEEN

ABSOLUTE ZERO SPEEDS TO TWICE SYNCHRONOUS SPEED FOR A GIVEN FREQUENCY OF EXCITATION (BEFORE ENTERING CONSTANT-HP RANGE)!

- SYMMETRICAL DUAL-PORTED TRANSFORMER TOPOLOGY

FOR HIGHEST POSSIBLE PEAK TORQUE!

- ENTIRE ROTOR ASSEMBLY IS NOT WASTED ASSEMBLY VOLUME AS IN ALL OTHER EMS BUT ACTIVELY SHARES WORK DURING THE ENERGY CONVERSION PROCESS!

- HIGHEST EFFICIENCY, LOWEST COST, SMALLEST SIZE, AND

HIGHEST PEAK TORQUE WITH WELL KNOWN, OFF-THE-SHELF TECHNOLOGY AND WITHOUT EXOTIC OR STRATEGIC MATERIALS (PERIOD)!

As the only electric machine system with a true symmetrical circuit topology, SYNCRHO-SYM is without extraneous space robbing and costly passive rotor assemblies that do not share in the energy conversion process, such as the permanent magnet rotor assemblies found in the synchronous PM-EMS, the squirrel cage rotor assemblies found in the induction EMS, the reluctance rotor assemblies found in the reluctance EMS, or the slip-ring assemblies found in the C-WRDF-EMS and field-wound (i.e., electromagnet) synchronous EMS. In effect, SYNCHRO-SYM will always have a



favorable comparison result to any other EMS even with the entire cost, inefficiency, and size of the passive rotor assembly of other electric machines completely removed from the comparison. As a result, the brushless SYNCHRO-SYM with an active rotor assembly (i.e., second armature), which is similar to the stator assembly but separated by a bearing assembly, is the simplest EMS available, which is contrary to ad hoc perception, particularly when SYNCHRO-SYM is confused with the C-WRDF-EMS. It can’t be over emphasize that SYNCHRO-SYM is the only brushless wound-rotor doubly-fed electric machine, which does not rely on speed-based asynchronous (i.e., induction) principles or obscure rotor temperature dependent impedances, and as a result, SYNCHRO-SYM has fully independent control of the rotor armature and “active” rotor real-estate. All other doubly-fed electric machines offer the low power, low cost electronic controller expected of doubly-fed electric machines but rely on speed-based induction principles, such as the so-called brushless induction and reluctance doubly-fed EMS that include the complexity, inefficiency and bulk of a passive but special rotor assembly that focuses induction between dual armatures of unlike pole-pairs squeezed into the stator assembly.

d. Conventional EMS Details With no indication of actual physical appearance or comparable size between the electronic controller and electric machine entity, Figure A gives an abstract illustration of a conventional singly-fed EMS, which includes the active stator armature assembly and the passive rotor assembly from any electromagnet (i.e., field-wound), EMS, PM-EMS, Induction EMS, or Reluctance EMS. For illustration convenience, the conventional electric machine entity is its well known radial-flux form-factor, which is a passive rotor assembly cylinder (i.e., dotted circle) inside a stator armature assembly cylinder of multiphase windings. The conventional singly-fed EMS has only one electrical port (i.e., singly-fed) connecting a multiphase AC electrical utility power of fixed voltage to a single armature winding set. The total EMS electrical power passes through a remotely mounted conventional electronic controller with some state-of-art derivative of Flux Vector Control to convert the AC utility power to motion-synchronized multiphase variable frequency AC for exciting the stator armature winding set. Disregarding loss, the total electrical power equals the total mechanical power from the shaft of the rotating rotor assembly. With the design of the armature winding set constrained by the flux saturation of the magnetic core material, which includes slots, wire gauge, winding turns, etc., the air-gap boundary area between the rotor and stator will be virtually the same between all optimally designed electric machine types with equal continuous torque density and stator armature power, including the permanent magnet EMS (assuming the bounded flux density of the PM can reach the same air-gap flux density as the armature winding set). When including back-iron to avoid magnetic leakage, the air-gap area determines the rotor and stator real-estate volume, with the rotor volume contributing nothing to the power conversion process except for providing the air-gap flux density, the shaft connection, and the mounting body for permanent magnet, squirrel cage winding, field-wound electromagnet, or



reluctance assemblies. In consideration, continuous power density, which is the product

of continuous torque density and the constant-torque speed range, is virtually the same between optimally designed singly-fed electric machine types with similar cooling methods per nominal frame size. The electronic controller includes an intermediate DC link stage between two stages of active electronics for bi-directional excitation power flow. The bi-directional power flow is ‘asymmetrical” because at any time, one electronic stage operates passively (i.e.,

Figure A



rectifying) with the other stage actively controlling flow. Consequently, extra harmonics and loss are always produced unless expensive active filtering with another complex stage of electronics and reactive components are introduced.

e. BEM SYNCHRO-SYM Working Details

With no indication of actual physical appearance or comparable size between the electronic controller and electric machine entity, Figure B gives an abstract illustration of SYNCHRO-SYM, which includes the Stator Armature Assembly and the Rotor Armature Assembly of a Wound-Rotor Doubly-fed entity (WRDF) but without the

Figure B



traditional multiphase slip-ring assembly connection to the rotor armature (e.g., the C-WRDF-EMS). For illustration convenience, the WRDF is a cylinder (i.e., dotted circle) of multiphase windings (i.e., rotor armature assembly) inside another cylinder of multiphase windings (i.e. stator armature assembly), which is its well known dual armature radial-flux form-factor. In this example, the stator active multiphase winding set (i.e., stator armature assembly of the WRDF) is directly connected with multiphase AC electrical utility power of fixed voltage. The Rotor Excitation Generator (REG) is the novel integral electronic controller of SYNCHRO-SYM that entirely replaces the slip-ring assembly and electronic controller of the C-WRDF-EMS. In this example, the front-end of the REG is connected directly to the multiphase AC utility in parallel with the WRDF stator windings. The back-end of the REG directly connects the rotor active multiphase winding set (i.e., rotor armature assembly) with motion synchronized multiphase variable frequency AC excitation (i.e., the proprietary and patented Brushless Real Time Controller). SYNCHRO-SYM has two electrical ports (i.e., doubly-fed) that separately power the stator and rotor armature winding sets with only the rotor power passing through the electronic controller (i.e., REG), which is half the total electrical power, if the rotor and stator armatures are equally rated. Disregarding loss, the total electrical power equals the total mechanical power from the shaft of the rotating rotor assembly. Explained in more detail in section 4 on page 20, Rotor Excitation Generator (REG), the REG consists of a position-dependent flux high frequency rotating transformer (PDF-HFT) with a similar arrangement of primary (i.e., stator) and secondary (i.e. rotor) phase windings as the WRDF entity but designed with low mutual inductance for high frequency operation. The PDF-HFT is stationed between two electronic stages of synchronous modulators-demodulators (i.e., modems with simple choppers) on the rotor and stator, respectively, which convert and isolate the low frequency input and output of the REG to PDF-HFT compatible high frequency. Highlighted by fine dotted lines, the “Rotating Body” or armature assembly of the WRDF is attached to the “Rotating Body” of the REG, which consists of the PDF-HFT secondary windings and one stage of synchronous modems, so both move freely but together to experience the same movement dynamics. As a result, the PDF-HFT becomes an electromagnetic computer (i.e., self-commutator) when complemented with proprietary conditioning techniques, which experiences the same mechanical and electromagnetic dynamics as the WRDF, and unlike inferior Field Oriented (i.e., Flux Vector) Control, REG excitation control of the rotor multiphase winding set becomes instantaneous and independent of amplitude or frequency of the input signal, which is referred to as Real Time Control (BRTC). The noticeable difference between the conventional EMS of Figure A and SYNCHRO-SYM of Figure B is the double power rating within the same package size and the half rated electronic controller with brushless “symmetrical” bi-directional power transfer. Furthermore, the rotor air-gap area, which is the same between all types of electric machines with equal stator armature design, determines the bounded stator and rotor volumes or armature sizes but unlike the conventional EMS, the rotor volume of SYNCHRO-SYM (with a multiphase winding set) actively contributes work to the power conversion process. As a result, the rotor volume is not passive and wasted. By



individually placing the stationary and rotating electronics within the core annulus of an axial-flux form-factor, only the axial flux SYNCHRO-SYM has the same rotor and stator assemblies for simple manufacturing, reduced inventory, and easy field service.

f. BEM SYNCHRO-SYM Unique Attractive Attributes A small set of theoretical studies of the well known C-WRDF-EMS from professional publications, such as IEEE Transactions, are available in APPENDIX III (Bibliography of Professional Publications) on page 46. Although the studies demonstrate the complicated attempts by established academia and industry to conventionally overcome the known limitations of instability and the slip-ring assembly, the studies conveniently highlight each of the following known attributes truly unique to the brushless and stable SYNCHRO-SYM:

Active Rotor Real-Estate: By eliminating reliance on low frequency or motion-based induction (i.e., asynchronous principles), which is only possible with a practical, independent, brushless, and phase locked real time control means that provides bi-directional multiphase electrical power connection to a second armature or “active” multiphase winding set placed on the rotor (i.e., doubly-fed) without speed-based induction, SYNCHRO-SYM is the only electric machine with rotor real-estate “actively” participating (or working) continuously in the energy conversion process in conjunction with establishing the rotating air-gap magnetic field. In contrast, all other electric machine systems, including the PM-EMS, have no practical electrical connection to the rotor real-estate with multiphase bi-directional electrical power flow to directly contribute to power production and as a result, the rotor real-estate “passively” participates in the energy conversion process by only establishing the rotating air-gap magnetic field. With rotor and stator real-estate each consuming about half of the physical volume of any electric machine; with the power rating of any armature or active winding set effectively determining the air-gap area or physical size of any electric machine; and with the sum of the power rating of all active winding sets determining the total power capacity of any electric machine, the doubly-fed SYNCHRO-SYM with at least equally active rotor and stator winding sets within similar physical volume inherently exhibits very high power and specific power density compared to any other EMS. This is equivalent to a superconductor-EMS operating with over 2 Tesla of air-gap flux density but without the complexity, cost, inefficiency, or real-estate associated with ancillary and cryogenic support equipment. [Without providing detail, SYNCHRO-SYM technology can bring superconductor machine systems closer to practical reality.] As a clear metric of power density while operating under the same voltage, frequency of excitation, torque, pole-pair count, and within the same package size, the SYNCHRO-SYM has a constant torque speed range of 0-7200 rpm @ 60 Hz with one pole-pair, which is twice the constant torque speed range and power of 0-3600 rpm for other EMS, such as the PM-EMS.

Low Cost High Efficiency Electronic Control: For another level of higher

efficiency and smaller size with significant cost reduction, the SYNCHRO-SYM integral electronic controller, called the Rotor Excitation Generator (REG), only



controls the power of the rotor active winding set for full system control, which is half (or less) of the total system power rating. Similar to any EMS, the REG takes on proportionally more power at speeds above the constant torque speed range (i.e., constant horsepower range) but at half the rate of other EMS. (Furthermore, SYNCHRO-SYM has reduced eddy losses.) In effect, the normalized power density of the electronic controller of SYNCHRO-SYM shows twice the power density of any other EMS electronic controller with the same optimizing design features available to all. With virtually all variable speed EMS requiring electronic control for practical operation or to meet 2015 efficiency deadlines, the cost, efficiency, and size of the controller should always be included for equitable system comparison, which is rarely the case except with SYNCHRO-SYM.

Low Loss Winding Core: With the same armature power rating under a utility

source of given voltage and frequency of excitation, the dual armature SYNCHRO-SYM shows twice the total system power as any singly-fed EMS, such as the PM-EMS, reluctance EMS or Induction EMS. Since similar electrical loss (i.e., I2R), core loss, and efficiency occur in similarly designed armatures of similar power rating and since electrical loss, core loss, and efficiency are always normalized relative to total system power, the dual-armature SYNCHRO-SYM with MMF included shows nearly the same normalized loss and efficiency as any PM-EMS with a similarly power rated stator armature winding set but nearly half the normalized loss and higher efficiency as any advanced singly-fed induction electric machine with the additional passive (or dissipative) rotor winding set of similarly rated MMF. However, when the essential electronic controller for practical operation of any performance electric machine system is correctly included in the comparison, SYNCHRO_SYM with a half power rated electronic controller always shows lower loss and higher efficiency overall. The same reasoning applies if SYNCHRO-SYM is designed with half power rated armature winding sets for the same total system power as the PM-EMS or Induction EMS contestant.

With hysteresis and eddy current loss are directly related to the excitation frequency and the square of the excitation frequency (or speed), respectively, but with hysteresis showing the significant loss at low speeds and eddy loss showing the significant loss at high speeds, the total core loss of SYNCHRO-SYM throughout its lower half of the constant-torque speed range varies between similar to much lower core loss as the PM-EMS operating throughout its constant-torque speed range. But at the upper half of its speed range, the core loss of SYNCHRO-SYM is significantly lower than the PM-EMS requiring up to twice the excitation frequency and voltage for the same constant-torque speed range.

No Exotic or Strategic Technologies: By using only copper and steel found in all

electric machines, SYNCHRO-SYM does not incorporate exotic materials, such as superconductor field-winding technology or high performance permanent magnets that use scarce samarium-cobalt or cartel-controlled neodymium-dysprosium rare earth materials. Contradictory to healthy supply and demand economics, China overwhelmingly controls the global supply of neodymium materials and virtually all



the stabilizing doping ingredient, dysprosium. The alternative, samarium-cobalt, is even scarcer more expensive material. Of more concern with the expected migration to an electric society, the future global demand for PM material is likely to outpace the entire global supply (including China) of minable raw material without new discoveries of sizable minable deposits. Furthermore, if the environmentally unfriendly mining and processing of these specific rare earth materials were considered, the advertized green status of the high performance PM-EMS would be seriously challenged. Although companies are renewing interest in ferrite with one-seventeenth the cost as a marketable solution to high performance magnetic materials, readily available ferrite PM materials with about one-tenth the BH energy product are much too delicate and volume consuming to be a viable replacement material that can competitively perform against the conventional Induction-EMS for the foreseeable future. Now considered strategic materials, renewed R+D investment for studying the efficient use of these rare-earth materials is quickly taking place rather than their complete elimination. Ironically, cartel affiliations, which already control over 90% of PM-EMS manufacture, are endorsing these efforts and sharing in the R+D grants while diverting R+D from more rewarding electric machine technology, such as brushless and stable wound-rotor synchronous doubly-fed technology. Furthermore, any material science effort to improve performance of PM materials, such as nanotechnology, will likely improve magnetic core material properties, which is beneficial and just as useful for all electric machines. Still, the US Department of Energy 2011 Annual Progress Report demonstrates PM and non-PM electric machine system R+D is vibrant today; particularly with its vested affiliates, such as Toyota, Honda, Hyundai, etc. With high coercivity and a persistent magnetic field, high performance PM eliminate magnetizing current and extends air-gap depth (e.g., 20%) for loser frame and bearing tolerance before magnetic leakage becomes the same issue as other EMS types, which questions the marketing veracity of so-called coreless PM-EMS. Furthermore, any theoretical flux density improvements marketed by magnetic path focusing techniques, such as Parallel Path, Internal Magnet, or Halbach Array arrangements, is bounded by core saturation limits (as for electric machines without permanent magnets) and the low residual flux density design limit of high performance PM materials despite its high BH product. Furthermore with no port connection for electrical or mechanical power, permanent magnets do not contribute work to the energy conversion process as sometimes perceived, which makes the entire mounting assembly, such as the entire rotor, wasted real-estate. Field Weakening, which provides higher speed bandwidth and reliable electronic control, has now become another holy grail of PM-EMS research. Field Weakening of PM-EMS always requires the introduction of magnetizing MMF, which is an inherent feature of transformer type electric machine systems, such as SYNCHRO-SYM or Induction electric machine systems, and field-wound synchronous electric machine systems that are all without extraneous PM materials and assemblies. Originally, the marketing advantage of the PM-EMS was no magnetizing MMF but now after absorbing market share, the goal of PM-EMS research is to supplement the



PM assemblies with magnetizing MMF for Field Weakening capability, which is seemingly blind endorsement of the PM-EMS perhaps instigated by the marketing ploy of the PM cartel. As a fully electromagnetic electric machine, which comprises no PM or exotic materials but only windings found in all electric machines, SYNCHRO-SYM accommodates any electric machine form-factor or power rating, particularly with its proprietary electronic controller rated for half power (or less depending on speed range). Peak air-gap flux density is nearly always bounded by the saturation of the magnetic core material as in all electric machines, particularly about the slot teeth; however, without the persistent but limited flux density of high performance PM but with PM demagnetizing potential (regardless of high coercivity), higher peak air-gap flux density is always safely and reliably achieved by winding MMF. Without the persistent magnetic field of a PM assembly, rotor and stator components can be field repaired or assembled without the same concern for safety, such as electrocution by induction, physical injury, etc., or without difficult handling logistics, such as special manufacturing, assembly, and field service tooling, etc. Without the stiff persistent magnetic field of PM, control and electronic reliability have been verified to statistically improve (in large wind turbine studies). Non-PM electric machines require magnetizing current to establish the air-gap flux and armature winding voltage in accordance to Faraday's Law. The magnetizing current component (i.e., vector) in transformer type electric machines (i.e, induction and synchronous wound-rotor doubly-fed) is always orthogonal to the active current (i.e., torque current) component and in worse case, is upward of 30% of the maximum torque current magnitude. The total current magnitude contributes to electrical loss in all winding sets according to the product of total current magnitude squared and winding resistance. As the vector sum of the magnetizing current component and the torque current component, the total current magnitude of transformer type electric machines is only 4% higher than PM electric machine systems in the worst case

(i.e., 04.13.01 22

with 1 as the normalized torque current) and is not the proportional 30% higher current magnitude that some PM marketers suggest. Furthermore, wound-rotor doubly-fed electric machines can share the magnetizing current between the rotor and stator armatures and in worst case, total current magnitude is 1% higher than PM electric machines (without considering the better power rating of doubly-fed). In contrast, increasing magnetizing current gives a proportional decrease in number of winding-turns. Under the same analysis, electrical loss due to magnetizing current varies from 9% to 2.3% more loss than the PM electric machine but the compounded electrical loss of the PM electric machine "system," which includes a full rated electronic controller, is always greater than the wound-rotor doubly-fed electric machine system, which includes a half-power rated electronic controller. This is the same for core loss

Highest Peak Torque: As the only electric machine with a truly symmetrical (i.e.,

dual-ported) transformer circuit topology provided by real time control of the REG,



the primary currents and secondary currents (beyond Faraday’s magnetizing current) associated with increasing air-gap magnetic flux in other machines are now neutralized. As a result, the operating principles of SYNCHRO-SYM accommodate much higher peak torque current without leading to the cumulative vector effects of core saturation, field misalignment, or damage experienced by all other electric machine systems, particularly for the PM-EMS. Peak torque (and torque current) of SYNCHRO-SYM is far beyond the highest torque of the closest electric machine competitor, the universal (i.e., electromechanically self-commutated) EMS, and factors higher than any other EMS competitor, including PM, Induction, and other doubly-fed induction electric machine systems. Like any EMS, safe operating conditions, such as duty cycle, are affected by peak torque current and as a result, the electronic controller must be appropriately rated; but only the electronic controller of SYNCHRO-SYM (i.e., REG) is conveniently rated for half the peak power over its extended constant torque speed range.

Adaptable: The symmetrical transformer circuit topology of SYNCHRO-SYM

can leverage any winding form-factor, such as concentrated low end-turn windings flaunted by PM-EMS technology, or the legacy of advanced research, examples, designs, improvements and commercialization available to any type of electric machine, including the C-WRDF-EMS, but without instability or a multiphase slip-ring assembly.

Much More: With a symmetrical circuit topology (i.e., dual-ported transformer)

under real time control, only SYNCHRO-SYM provides rock solid voltage and frequency following (i.e., phase lock-loop). As a result, SYNCHRO-SYM shows at least: 1) controllable leading, lagging, or unity power factor adjustment; 2) symmetrically stable motoring or generating modes of operation; 3) fault tolerance; 4) low voltage ride through (i.e., LVRT); 5) intentional or non-intentional islanding and synchronous connection at any speed; 6) individual phase control with a similar benefit in power component rating (i.e., 1.73 advantage for 3-phase systems); 7) no bulky and inefficient low frequency components, such as a DC Link Stage; and 8) virtually pure sinusoidal excitation signals without common-mode, distortion or harmonic content that commonly leads to insulation failure, bearing failure, heating, and power loss in all other EMS.

g. BEM SYNCHRO-SYM Perceived Concerns: As the “only” electric machine with “active” rotor real-estate, SYNCHRO-SYM easily eliminates any perceived concerns:

REG rotor electronics seem to impose cooling and reliability issues but rotor based electronics have been commercially popular for decades to actually improve reliability or performance of the EMS, such as high power turbo-alternators with rotor electronics for brushless excitation of the field-winding (i.e., electromagnet), diagnostic and measurement electronics, etc. More importantly, rotor electronics as implemented by the REG is the only means to achieve the attractive attributes of highest power density, lowest cost, highest efficiency, and highest peak torque



provided by brushless, synchronous, and stable control of active rotor real-estate in a true symmetrical WRDF topology; and rotor electronics as implemented by the REG electronically eliminates the need for exotic materials or technologies, such as PM or superconductors, but with better performance. Furthermore, the preferred axial flux form-factor conveniently exposes the rotor to the same cooling surface area as the stator, which contradicts conventional wisdom of confining dissipative components to the stator, such as active windings. With the half-rated electronic controller of SYNCHRO-SYM, the REG rotor electronics (i.e., one of two stages) dissipate only one-quarter the chassis power of the conventional electronic controller and as a result, require less rotor cooling. Regardless, fast, robust, high temperature, high power electronic components operating to 250° C (e.g., SiC, etc.), which is beyond the operating temperature of winding insulation, are already entering the market while achieving the highest power density in conventional electronic controllers. [If compared to other electronic control, the half power rated REG effectively doubles the normalized power density of the electronic controller.]

Although integrated electronic control is the Holy Grail (and fast approaching) for

any EMS, integrated electronic control is inherent with SYNCHRO-SYM. However, remotely mounted electronics have the convenience of residing in an air conditioned room with separately long, high frequency electrical cabling connection to the electric machine under control, which are custom engineered to reduce noise and reflection damage caused by transmission line effects as a result of hard common-mode electronic switching by conventional electronic controllers (e.g., switching edges > several hundred kHz). In contrast, SYNCHRO-SYM uses standard electrical wiring local to the installation site and like any EMS in the most extreme environments, a distribution of inexpensive plastic tubing to remotely supply cooling medium could be introduced, all of which are considerably simpler and less expensive than set-aside air-conditioned rooms and engineered high frequency high power electrical distribution buses.

With two means for reversing SYNCHRO-SYM rotation, simply reversing

rotation (without phase switching) increases REG power flow but at the rotor power rate, which is half (or less) of the total power.

With twice the constant torque speed range (and power) for a given excitation

frequency and voltage, SYNCHRO-SYM pole-pairs double to provide the same speed at the same excitation frequency as other EMS. But with the inherent half power rotor and stator assemblies for the same torque, SYNCHRO-SYM always shows half the total core volume as other EMS with the diameter increasing less than 30% for the same number of slots per pole-pair and not doubling as expected with all other EMS. Furthermore, Power Stacking Technology (PST) proportionally substitutes diameter for stack length (or vice-versa) during design while improving cooling, which more than satisfactorily addresses the already manageable diameter.

Forgoing PM or exotic technologies, SYNCHRO-SYM is purely an AC EMS

with both ports individually excited with AC (i.e., dual-ported or doubly-fed) of half



total power rating and at least one port excited with speed-synchronized AC. On first perception, this seems to complicate a DC application, such as an EV, by requiring two ports of electronic control. But each controller is rated for half the power with a combined power rating and cost equal to the full rated electronic controller of any other EMS. Furthermore, Klatt has invented an advanced electrical power distribution bus (A-EPDB), which greatly simplifies the DC-AC interface while providing better efficiency, lower cost and higher reliability over other electrical power distribution methods for DC or non-standard frequency applications.

Considering all electric machines follow the same operating relationships, which are simultaneously base on Faraday Law, Ampere Law, and Lorentz’s Relations, with virtually the same slot count, pole-pair count, air-gap flux density, wire size, voltage, frequency, duty cycle, and cooling design choices for winding sets, all EMS show about the same “continuous” torque density, if optimally designed with the same choices equally available to all. [Note: Comparisons against manufacturer’s “marketed” specifications should never be considered without the same design, manufacturing, construction, material, cooling, and duty cycle choices equally available to all.] However, as the only electric machine with active rotor real-estate, nothing approaches SYNCHRO-SYM, if cost, efficiency, continuous power density, peak torque, and peak power density are the deciding factors! See APPENDIX I (EMS Design Constraints) on page 37. 4. Rotor Excitation Generator (REG)

a. BEM Rotor Excitation Generator (REG) The proprietary Rotor Excitation Generator (REG) is the integral electronic control component of SYNCHRO-SYM. Revolutionary in operating principles, the REG: 1) automatically provides absolute positioning mechanism with the inherent “electromagnetic processing” of the PDF-HFT while under the same motion dynamics as the WRDF, which is essential for guaranteeing stable, variable speed, constant frequency (VSCF) “synchronous” operation at any speed, position or perturbation, particularly for stable wound-rotor doubly-fed synchronous control; and 2) independently propagates distortion-free speed-synchronized multiphase excitation power to the rotor multiphase winding set without motion-based induction or electromechanical contact of any kind (i.e., brushless). The REG servo method of control, which is comparable to the “electromagnetic” processing of a Resolver or Selsyn, is appropriately designated Brushless and Stable Real Time Control (BRTC). Furthermore, the unique switching modulation techniques and circuit topology of the REG, which uses off-the-shelf components, always drives the low frequency windings of the WRDF entity and the utility power with motion-synchronized sinusoidal signals that are virtually free of common-mode, distortion, or harmonic content.

b. Conventional EMS Electronic Controllers In direct contrast to the REG with BRTC, today’s state-of-art control method, such as derivatives of Flux Vector Control, perform time consuming, imprecise, and interdependent “electronic processing” for: 1) offline measurement of frequency, speed



and position; 2) offline transformation of coordinates for realistic electronic calculations; 3) offline estimation of time-constants; and 4) offline frequency synthesis of excitation with common mode modulation that directly drive the windings of the electric machine and the utility power with high frequency harmonics, which lead to insulation failure, bearing failure, power loss, and poor power quality unless the ancillary cost, inefficiency, and size of extra mitigating measures are introduced. The limitations become obvious at low speeds or frequencies, when the change with time (i.e., slope) of the measured or synthesized signals becomes immeasurable and phase adjustment becomes untimely and inaccurate for satisfactory control. Furthermore, the power of the electronically synthesized excitation is propagated to the rotor winding set of a C-WRDF-EMS by the extra cost, inefficiency, complexities, and real-estate of a multiphase slip-ring assembly.

c. BEM REG Operating Details Basically, the REG includes a PDF-HFT stationed between two electronic stages of synchronous modulators-demodulators (or modems) on the rotor and stator, respectively. Each phase has its own synchronous modem, which are actually bi-directional chopper circuits that are as simple as those chopper circuits used in induction heating controllers. By sampling or gating the modems in synchronism (i.e., synchronous modulation-demodulation) with special proprietary modulation techniques, individual synchronous modems modulate or demodulate each low frequency AC phase (or DC) signal applied to the input or outputs of the REG with a high frequency differential (i.e., bipolar) carrier. As a result, each applied signal to the PDF-HFT is the high frequency carrier signal with a modulation envelope of the low frequency AC phase signal, which precisely captures the signatures of the low frequency AC on each side of the differential carrier for modem reproduction. Synchronous gating by the modems virtually confines (i.e., gates) the high frequency carrier signal to the PDF-HFT, which is obviously designed for high frequency operation, and away from the low frequency inputs or outputs of the REG, which connect to the AC utility source or the low frequency windings of the electric machine (e.g., WRDF). As a result, the input and output connections of the REG experience nearly pure sinusoidal AC phase signals with very little filtering. Conveniently, the differential carrier signals inherently provide soft (i.e., resonant) switching at the zero crossing of power to reduce component stress and switching loss while benefitting from the reactive impedance of the circuit. Furthermore by appropriately sampling (i.e., gating) the synchronous modems with proprietary modulation techniques, the periodic magnetic energy stored in the PDF-HFT can be shared between phase windings to contrive sinusoidal multiphase AC excitation of any motion-based frequency (e.g., 0-60 Hz) or phase offset. In addition, by allowing relative movement between the primary (stator) and secondary (rotor) windings of the PDF-HFT with an air-gap, any motion-based frequency or phase offset of sinusoidal multiphase AC can be produced by relative movement between the rotor and stator at the appropriate speed and phase offset, which is another form of sharing magnetic energy of the PDF-HFT that follows virtually the same operating principles as the WRDF. Any 3-phase AC signal (e.g., for instance) of fixed frequency (say 50/60 Hz) at the input of the REG would be automatically and instantaneously transformed to another 3-phase AC signal of variable frequency or phase offset with modulation components of relative



speed and position solely by the inherent electromagnetic processing of the PDF-HFT, which experiences the very same dynamic principles of motion-based induction between the rotor and stator windings of a 3-phase C-WRDF-EMS but with the electrical and mechanical effects of significantly lower mutual inductance of the high frequency PDF-HFT. By replacing the slip-ring assembly (and controller) of the C-WRDF-EMS with the REG and mechanically attaching rotors of the WRDF and REG (and PDF-HFT) to provide the same movement dynamics while electrically connecting AC phases, the precise rotor power excitation for synchronous operation of a C-WRDF-EMS is “automatically” and “instantaneously” satisfied without “offline electronic” processing intervention, without regard for rotor movement, and without reliance on motion-based induction or slip-ring assemblies; hence, the BRTC of SYNCHRO-SYM. By automatically alleviating the elusive control for complex variable motion-based excitation frequency from offline electronic processing, torque control becomes a simple singular process of controlling torque current magnitude without regard to motion or position, which is akin to the admired simple control of the self-commutated universal (i.e., DC) EMS but without the unreliability, real-estate consuming, or low control resolution of electromechanical commutation. More importantly, the full bi-directional power of the low frequency, motion-based multiphase AC power propagates to the rotor winding set through a direct multiphase high frequency AC-to-AC conversion method: 1) without the bulk and inefficiency of low frequency components, such as a DC Link Stage and line reactors; and 2) without the bulk, cost, inefficiency, and power capacity constraints of electromechanical contacts (i.e., brushless) or extra winding sets to provide motion-based induction; but instead, with the compactness and efficiency of a high frequency transformer (i.e., PDF-HFT) with low mutual inductance, shortened winding-turns and low resistance (and loss) as stipulated by high frequency operation. Only with the circuit topology of a PDF-HFT surrounded by synchronous modems: 1) forms a gyrator circuit topology where the current phase can be adjusted electronically in relation to the port voltage, regardless of magnetizing current, or adjusted manually by changing the physical relation between the WRDF and PDF-HFT stator assemblies, both of which provide comprehensive leading, lagging, and unity power factor control, regardless of magnetizing current; 2) provides inherent step-up-down voltage-current transfer ratio; and 3) exhibits a seamless connection of multiple units consisting of additional isolated PDF-HFT phase windings and low cost synchronous modems to easily provide moderate to high voltage scaling by series connections or moderate to high current scaling by parallel connections.

d. REG versus Conventional EMS Controllers Virtually all conventional state-of-art electronic controllers incorporate a bulky and inefficient intermediate DC Link Stage between at least two stages of electronics with twelve active switches to provide AC-DC-AC conversion in a separate remotely mounted chassis with little engineering concern for wasted packaging space (e.g., back-to-back converter). Typically with four switch junction drops in the total conducting circuit path, each electronic stage for the conventional controller is rated for the full conversion power and consists of six active electronic switches for a total of 12 switches across the two stages, which are operating at effectively full duty cycle switching at the “peak-to-peak” AC phase voltage of the DC Link stage (i.e., 1.73 for 3-phase systems) and more than



peak AC “phase” current flow (i.e., 1.3 for 3-phase systems). See APPENDIX II (DC and AC Power Transfer) on page 39. Since the DC Link Stage always forces uncontrolled rectification at given times with the high dissipation and poor signal quality of associated harmonics, more stages of high power electronic switches and reactive components should be introduced in high performance applications to provide active correction for some degree of excitation smoothness. Losses cumulate with the number of switch junction drops, the low frequency reactive components required by the DC Link Stage, such as line reactors, transformers, filters, etc., and as an integral component of C-WRDF-EMS control, the necessary multiphase-slip-ring assembly for propagating electrical power to the moving multiphase active winding sets of the rotor. In contrast, the simpler REG conveniently replaces the entire real-estate of the slip-ring assembly and intermediate DC Link Stage with a compact, efficient PDF-HFT between two similar electronic stages on the rotor and stator, respectively, for AC directly to AC conversion. As a result, the REG becomes an integral part of SYNCHRO-SYM. With the 8 switch junction drops in the conducting circuit path for a full bridge circuit topology (e.g., 4 switch junction drops for a push-pull circuit topology), each electronic stage is rated for half the conversion power but consists of twenty-four active electronic switches per stage for a full bridge circuit topology (e.g., 24 switch junction drops for a push-pull circuit topology). The switches operate at only half duty cycle switching, peak AC phase voltage and current. Because of true wound-rotor synchronous doubly-fed operation, the power rating is one half of the total power. After reviewing APPENDIX II (DC and AC Power Transfer) on page 39, the electronic switch loss of the REG is better than ½ the conventional electronic controller (even with 8 switches versus four switches in the conduction path) and the electronic switch cost of the REG is better than ½ the conventional electronic controller (even with 48 switches versus 12 switches in the conduction path). As a result with up to twice the combined advantage of the conventional controller for electronic switch cost, size, and electrical loss and with up to one-four-hundredths the proportional physical size, number of winding-turns, or electrical impedance between the PDF-HFT designed for say 24 kHz and the SYNCHRO-SYM designed for 60 Hz (60 Hz ÷ 24 kHz), the compact REG integration into the SYNCHRO-SYM chassis is conveniently possible. Specifically designed for high frequency operation, the PDF-HFT, which effectively replaces the low frequency DC Link Stage and complementary reactive components of the conventional electronic controller, shows lower loss overall without considering the lower power rating of doubly-fed operation. Although the necessary air-gap of the PDF-HFT introduces low reactive impedance due to leakage, the air-gap more importantly evenly distributes core flux and conveniently implements soft switching (i.e., resonant switching) without additional reactive components to effectively eliminate the higher harmonic and switching loss.

e. REG Assessment Integration of power and control electronics into the rotor or stator of the EMS chassis follows today’s goal (or practice) of eliminating field integration and tuning with associated cost while improving overall performance and physical density. The unrelated development and commercialization of the so-called new Variable Frequency



Transformer for the flexible AC transmission system (FACTS) [Hydro-Quebec’s Langlois substation] and the high power high frequency electronic transformers for the compact, low cost, and efficient replacement of low frequency AC utility transformers demonstrate the belatedly catch up by the establishment with loosely comparable technology but more importantly, conveniently provide third party verification of REG technology. Well acquainted with the back-to-back (i.e., DC Link Stage) converter limitations, Matrix Converter topologies, which will always rely on Flux Vector Control, are constantly being conceived by the electric machine establishment but will never achieve the simplicity, efficiency, high torque, and low cost of BRTC provided by the REG.

f. Effective Power Switch Utilization For AC and DC Control A PM electric machine system can satisfactorily peak to 150% of continuous torque per nominal frame size, an induction electric machine system can satisfactorily peak to about 250% of continuous torque, a commutator DC motor system can satisfactorily peak to 500% of continuous torque, but because of dual-ported transformer physics, SYNCHRO-SYM can satisfactorily peak to over 800% of continuous torque (or more by design) per nominal frame size.1 Beyond these peak torque values, core saturation overwhelms MMF (but less so with SYNCHRO_SYM), which is a function of current squared, with little torque production but considerable dissipation and permanent magnet damage if applicable. Obviously, auxiliary cooling or discontinuous operation must be employed to keep the electric machine within the safe operating area. Just as important, the electronic controller must be rated for the high current levels required to reach peak torque. The following analysis considers the peak power of the electric machine or three phase AC load is product of voltage and current (V*I) and as a result, the AC power across each switch (i.e., power semiconductor) in series with the load is V*I. The premise of this discussion considers the power semiconductors to be the cost driving component of any electronic controller, which can be considerably more than twice the cost of the electric machine itself. Furthermore, a very reasonable consideration between cost or efficiency and the power rating of the switch is a direct 1:1 relationship (e.g., a doubling in power rating of a power semiconductor, such as an IGBT, will double the die size and material, doubles the manufacturing cost; doubling the breakdown voltage will double the junction drop; Because of the transistor junction as a logarithmic function, increasing the current does little to junction drop). The reader is encouraged to review APPENDIX II (DC and AC Power Transfer) on page 39, which shows the following cost-performance analysis of the REG circuit topology compared to the conventional circuit topologies. DC machine: Since three phase AC power is the traditional means of electric power distribution, the DC electric machine system (i.e., commutator DC electric machine with electronic

1 The dual-ported (i.e., symmetrical) transformer technology of SYNCHRO-SYM reduces peak current to the voltage drop across the winding resistance. For other EMS, the voltage drop is across the winding impedance, which includes the inductive reactance. Furthermore, SYNCHRO-SYM has a inherent step-up-down electronic transformer to increase voltage drop.



control) needs a chopper circuit topology of at least 8 switches for asymmetrical control of bi-directional power flow (e.g., 6 switches for the Primary Stage between a three phase AC source and the DC Link stage with an Secondary Stage of 2 switches (i.e., bi-directional switch) to control the DC power to the DC electric machine. Without additional switch complexity, the bi-directional power flow is asymmetrical because the Primary Stage is rectifying during motoring mode (i.e., AC power flows to the DC link stage), which causes excessive harmonic distortion on the multiphase AC power distribution system. Furthermore, the switches must support the full power of the electric machine but to provide the same power as a three phase AC, the power rating of the switches is 1.73 V*I, which is the DC Link Stage (apparent) power. Cost Factor for power switches (only):

Note: Emphasized by the historical migration from DC to AC electric machines, the electromechanical commutator of the DC electric machine system is expensive and maintenance intensive, which can dramatically increase the overall cost of the system. PM or Induction machine: The dual stage inverter with an intermediate DC Link Stage is the most popular electronic controller for electric machine systems, including PM electric machines. Power across each switch is V*I*1.73 or the power of the DC Link Stage. The number of devices in a totem pole arrangement is 12 for asymmetric control of bi-directional power flow when motoring or generating. The bi-directional power flow is asymmetrical because at any time one of the two stages (i.e., primary or secondary stage) is operating as a rectifying stage, which puts harmonic distortion on the electric machine windings or the AC power distribution. More symmetrical control can be approached by increasing the switch complexity (e.g., 24 switches instead of 12). Cost Factor for power switches (only):

Cost Factor: PM Electric Machine System [Power Semiconductors]

Continuous Torque: 12*1.73 * 1.3 * (or 26.99)

Peak Torque: 2.5* 12 * 1.73 * 1.3 * (or 67.47) (250% Continuous Torque)

Cost Factor: DC Electric Machine System [Power Semiconductors]

Continuous Torque: 8 * 1.73 * 1 * (or 13.84)

Peak Torque: 5* 8 * 1.73 * 1 * (or 69.2) (500% Continuous Torque)



Note: There are other ancillaries that are not considered, such as the extravagant cost of the cartel controlled PM materials and the complex manufacturing and field service procedures for PM electric machine systems. Compared to the power semiconductors, the low frequency and bulky chokes or capacitor banks of the DC link stage show the highest loss, physical size, and the cost. SYNCHHRO-SYM: The Rotor Excitation Generator (REG), which is the real time controller of SYNCHRO-SYM, incorporates no DC Link Stage but comprises 48 semiconductors in a full bridge arrangement for symmetrical control of bi-directional power flow (i.e., motoring and generating). Unlike asymmetrical power flow of conventional DC and AC electric machine systems, symmetrical power flow as only the REG provides virtually eliminates harmonic distortion and associated filtering requirements. The power across the switches is the phase power (V*I) and not the phase-to-phase power (1.73V*I) of a DC Link Stage for a 1.73x cost factor advantage already introduced in the DC and PM torque. Doubly-fed principles allow the power through the REG to be one-half the total power of the electric machine rating for another 2x cost factor advantage. Furthermore, the switches operate at half the duty factor (i.e., full bridge with resonant or soft switching) and as a result, the switches can operate at twice the rated continuous current because of lower temperature rise with proper cooling for another 2x cost factor advantage.

Note: The twice continuous current factor while running half-duty cycle is documented in data sheets. Furthermore, a half power rated semiconductor (e.g., IGBT of half the current rating or half the voltage rating) has about half the die size with half the cost and half the junction drop, which is tantamount to half the dissipation.

Table 1 Cost Factor Comparison [Power Semiconductors]

Continuous Torque/Power

Peak Torque/Power @ Maximum

Peak Torque/Power @250%

DC Electric Machine System:

13.84 69.2 (500% of Continuous)

34.6

Cost Factor: SYNCHRO-SYM [Power Semiconductors]

Continuous Torque: 48 4*1 * 1 (or 12)

Peak Torque: 8*48 4*1 * 1 (or 96) (800% Continuous Torque) 2.5*48 4*1 * 1 (or 30) (250% Continuous Torque)



PM Electric Machine System:

26.99 67.47 (250% of Continuous)

51.9

SYNCHRO-SYM: 12 96 (800% of Continuous)

30

The Cost Factor Comparison Table 1 shows the power semiconductors for SYNCHRO-SYM are about half the cost of the DC electric machine system at continuous torque rating and approximately one-third the cost of the PM electric machine system (or any electric machine), while providing symmetrical bi-directional power control and by far, the highest peak torque potential. Even at the highest peak torque, SYNCHRO-SYM is considerably more cost effective when normalized between electric machine system. Note: The extra cost factor associated with the DC Link Stage or the HFT were not included nor were the extra cost (loss and size) factor associated with the mechanical commutator of the DC electric machine or the delicate high performance permanent magnet material of the PM electric machine. But with the cost of the DC Link Capacitors higher than the cost of the power semiconductors, the cost factor of the HFT, which is compact and efficient because of its high frequency operation, should be comparable if not better than the cost factor of the DC Link Stage.

g. Effective Power Switch Loss Factor For asymmetrical bi-directional power control, there are 4 switch junction drops per phase (i.e., 2 junction drops for the primary stage and 2 for the secondary stage) when the power conditioning circuit of the electronic controller for either the PM electric machine system or the DC electric machine system is conducting. Furthermore, the switches must support the full power of the electric machine and DC Link Stage, which experiences the phase-to-phase voltage (i.e., 1.73 factor). The rated voltage junction drop across the switch is directly proportional to power rating of the switch. The normalized switch power dissipation (i.e., loss) for either the DC or PM electric machine system is 4*1.73*1.3 or 9 (see APPENDIX II (DC and AC Power Transfer) on page 39). For symmetrical bi-directional power control, SYNCHRO-SYM with a full bridge configuration has 8 switch junction drops per phase (i.e., 4 junction drops for the primary stage and 4 for the secondary stage) when the power conditioning circuit of the REG is conducting. In accordance with SYNCHRO-SYM, the REG only supports the rotor power for full system control, which is half the power of the system for an advantage of 2 over the conventional controller. Furthermore, each switch must support the voltage of the AC phase and not the phase-to-phase voltage (or DC Link Stage). Furthermore, the switch rating for a half duty cycle circuit topology is one half for an additional junction drop advantage of 2, which is documented in IGBT data sheets. The normalized switch power dissipation (i.e., loss) for SYNCHRO-SYM is 8 ÷ (2*2) or 2, which is 22% of the normalized loss of the DC or PM electric machine system.



Note: SYNCHRO-SYM, which is a wound-rotor synchronous doubly-fed electric machine system, shows twice the power as the singly-fed PM or DC electric machine systems for a given current and voltage rating of the electronic controller. This advantage for SYNCHRO-SYM can be assumed by its wound-rotor electric machine entity or by its electronic controller (REG) entity. The Effective Power Switch Loss Factor analysis assumed the loss advantage by its electric machine entity and not for the REG entity, which otherwise would have provided an additional 2x advantage for the REG analysis. 5. BEM Power Stacking and Smart Manufacturing Tool Technologies

a. BEM Axial Flux Form-Factor Since SYNCHRO-SYM has active (or working) power on both the rotor and stator, which is better served with an axial-flux form-factor, BEM has patent pended a Power Stacking Technology (PST) and a Smart Axial-Flux Manufacturing Tool (SCMT) for vertical integration of SYNCHRO-SYM technologies. In contrast to the classic radial-flux format, the axial-flux form-factor provides at least: 1) inherently equal cooling exposure of the rotor and stator assemblies; 2) centralized mounting of each half of the compact, high frequency REG conveniently within the annulus of the WRDF rotor and stator core, which otherwise would be wasted space in other EMS in addition to the wasted space of their passive rotor assemblies; 3) single inventory of duplicate rotor and stator assemblies as only SYNCHRO-SYM can provide; 4) better air-gap tolerance during high speed operation with consistently higher air-gap flux density potential; 5) simple outside-in automated winding approach; and 6) inherent structural security of the moving windings directly against the core structure during high speed operation (which is an expressed concern for the radial-flux WRDF regardless of its merits but ironically, not a published concern for the more delicate PM-EMS structure).

b. BEM Power Stacking Technology With virtually the same component design, structure, and self-contained controller stage for the rotor and stator assemblies provided only by SYNCHRO-SYM technologies and without the persistent magnetic fields of PM, Power Stacking Technology: 1) accommodates individual field replacement of rotor or stator assemblies with a single inventory of the same self-contained components and without safety or special tooling concerns; 2) provides scalability, commonality, and modularity with failsafe operation, since the stack continues to operate regardless of individual component failure, albeit at reduced power capacity; 3) provides field replacement accessibility for individual components of the stack from a single component inventory; 4) accommodates different speeds, torques, and application specifications by conveniently interchanging power stack length and diameter; and 5) accommodates multiply higher power by adding a single inventory of components to the stack.

c. BEM Flexible Axial-Flux Smart Manufacturing Tool To compete with and improve against other patented axial-flux manufacturing tooling, BEM has patent pended its own Flexible Axial-Flux Smart Manufacturing Tooling with a more cost-effective approach, which provides less cutting stress on delicate high performance magnetic core material, such as thin or amorphous ribbon material, and



provides a low cost manufacturing method for the timely universal construction of a precision axial flux core with structural frame but without expensive pre-manufactured precision structures and castings. Specific to SYNCHRO-SYM, the core of the PDF-HFT can be built in conjunction with the core of the WRDF with amorphous magnetic ribbon, which is compatible with high or low frequency operation. 6. BEM Short Range Electrical Power Distribution Bus or (EPDB) Electric road vehicles, electric ships, etc. (EV), which are propulsion (or generating) applications, or large industrial applications incorporate at least one electrical power distribution bus (EPDB) to remotely connect distributed EMS or other electrical apparatus to distributed power sources over a short range (< 1000M), such as batteries, generators, flywheel storage apparatus, etc. Most likely consuming or producing the majority of electrical power on the EPDB, the connected EMS generally determines the power capacity of the EPDB. But all EMS have at least one armature or active multiphase winding set that must be excited with multiphase variable frequency AC (MPVF-AC) excitation for practical torque production under motion and as result, a DC-EPDB is commonly proposed because a single stage of active electronics can be removed from the MPVF-AC electronic controller of the EMS and consolidated into the DC-EPDB to reduce component count. However for high performance applications, which require smooth symmetrical control of MPVF-AC excitation power, such as EV applications, the electronic controller requires the minimum classic configuration of two stages of active

Figure C



electronic conversion on each side of a DC Link Stage with another stage of active electronics and reactive components for active power correction and regeneration. Different from passive rectifying diodes, only active electronics, which are controllable gating transistors, can control bi-directional power (albeit asymmetrically), voltage levels on the DC bus, and torque of the EMS with the required precision during high performance motoring or generating.

a. Conventional High Performance DC EPDB The conventional high performance DC-EPDB is shown in Figure C with solid borders lines highlighting minimal essential modules: 1) the power module converts DC electrical power for other apparatus, such as the EMS; 2) the DC battery or storage; 3) the step-up-or-down transformer modules, which could be placed between power modules to meet different voltage requirements; and 4) the contactor module to disconnect the battery. Additional modules, such as the optional dotted modules, can be added by tapping into the DC-EPDB along its length. The step-up-or-down transformer module incorporates electronic AC conversion circuitry to interface to the DC-EPDB, which may include high frequency conversion to reduce the bulk and loss of the transformer. Passive or active filtering protects the low frequency sides from hard high frequency switching modulation across a DC Link. With this modular configuration, the appropriate impedance of the self-contained DC Link Stage will be automatically applied to the DC-EPDB as power modules are added to the bus. Still, the power modules are bulky and inefficient because of low frequency chokes, transformers, and bypass capacitors of the DC Link Stage. Instead of DC, low frequency AC with 60 Hz, 400 Hz, etc. would show similar operation and module support. Instead of a PM-EMS, any doubly-fed EMS, such as SYNCHRO-SYM, would require independent AC excitation to both stator and rotor windings by two electronic controllers (for instance) to satisfy doubly-fed principles of two ports of multiphase AC excitation. Using SYNCHRO-SYM for the example in Figure C, each REG is rated for half the power with the sum equal to the cost, loss, or size of the single PM-EMS controller. More than one DC-EPDB with appropriate failsafe connection means may be incorporated to guarantee high reliability through redundancy. An electronic shut-off of the DC-EPDB always occurs at full power and at the high frequency of electronic switching, which generates stressful traveling and standing waves of several hundred kHz or more. [At least one serious and unsolved characteristic that is keeping DC utility distribution systems from application is mitigating reflected traveling and standing wave stress during full power shutoff; particularly during emergencies.] The high performance DC-EPDB is noticeably complex for high performance control of bi-directional power; particularly, when comprising doubly-fed EMS. In a minimal configuration, Figure C has two full rated electronic stages for each PM-EMS or four full rated electronic stages for the motor and for the generator with one full rated electronic stage for the battery contactor with a combined rating of “five” full rated electronic stages of cost, size, or electrical loss.



b. BEM Advanced EPDB Strategy The DC-EPDB is not the best EPDB for doubly-fed electric machines, which need two ports of multiphase AC power, and as shown in Figure C, the DC-EPDB complicates the circuitry needed to implement a Power Electronic Build Block (PEBB) concept (PEBBC) for seamless connection to any power requirement, such as single or multiphase AC of any frequency and voltage or DC of any voltage. BEM provides a patent pending EPDB solution called the Advanced EPDB (A-EPDB) for simple synchronized bi-directional power connection between SYNCHRO-SYM technology, for instance, and any power source, such as a battery in an electrical vehicle application. A strategic goal is to lower the cost, the weight, and the amount of material used in the EPDB. Certainly raising the voltage of the EPDB would lower current and amount of expensive copper used (i.e., wire) but would complicate the power electronics. Significantly raising the AC operating frequency beyond 400 Hz proportionally reduces the size and weight of reactive components, such as transformers, filtering, etc., but frequency should be kept below the transmission line threshold to eliminate compensation requirements for traveling and standing wave effects. For instance, an EPDB operating at 24 kHz has sinusoidal signal wavelength of 1.25 x 104 meters (3 x 108 (speed of light in M/sec) ÷ 24 x 103 cycles), which is at least ten fold longer than the anticipated length of any EPDB (e.g., several hundred meters) in an EV or propulsion application and by rule of thumb, the EPDB would not show transmission line effects of any significance. Note: Under the same reasoning, a utility distribution bus, which spans miles or hundredths of miles, is better served with low frequency AC (i.e., 50 or 60 Hz) or DC to minimize transmission line effects. Although a high frequency AC bus has the same resistance as a DC bus, since both must support the same power with the same amount of copper (while disregarding Litz wire to compensate for skin effect), the inherent distributed reactive impedance of capacitance and inductance, which ideally neither consume nor dissipate electrical power, introduces circulating currents that lead to additional dissipative losses in the circuit path. But the loss impact is minimal because circulating current and active current are orthogonal phasors, which do not accumulate linearly, and the magnitude of circulating current can be minimized by balancing power in and out of the bus. Besides, manageable reactive impedance is useful for implementing soft-switching with smooth switching edges, which eliminates high frequency transmission line effects experienced by power distribution buses between remotely placed conventional electronic controllers with fast-edge hard-switching and electric machine pairs. Furthermore, human audible noise is eliminated with higher frequency but radiation may be more pronounced in secure environments under electronic surveillance, which would have to be addressed by engineering, shielding, etc. for these circumstances.

c. BEM Advanced EPDB (or A-EPDB) Proprietary details of the A-EPDB will be supplied to appropriate parties but provides a simple, compact, low cost PEBBC support that interfaces to any bi-directional, frequency (e.g., AC or DC), number of phases or voltage power requirement. By simplifying the unique circuit topology of the REG as shown in Figure B with the removal of a single stage of power electronics from one side of the PDF-HFT (i.e.,



modified REG), an isolated patent pended Modulated High Frequency Multiphase AC EPDB or Advanced EPDB (A-EPDB) with high performance symmetrical control of bi-directional power flow exists between modified REG(s) as shown in Figure D. [Compare the extra stage of electronics in the REG blocks of Figure B or Figure C with the modified REG blocks of Figure D.] The modified REG is a simple, compact, low cost PEBB circuit with an inherent transformer for interfacing to any frequency, phase or

voltage power requirement. The modulation envelope can be 50Hz, 60 Hz, 400 Hz, etc. on a synchronized soft-switched, smooth edge sinusoidal high frequency differential carrier but 50/60 Hz is envisioned for compatibility with the abundance of commercially available 50/60 Hz apparatus. Without going into implementation detail, multiple SYNCHRO-SYM (with the modified REG configuration) can be connected through the common A-EPDB with less complexity than the DC-EPDB example as clearly shown by comparing Figure D to Figure C but more importantly with both armatures supplied with AC, the SYNCHRO-SYM continually operates as truly wound-rotor doubly-fed with the attractive attributes of smallest size, lowest cost, highest efficiency, and highest peak torque (and power) of any electric motor or generator system and without exotic or strategic materials. The minimal essential modules for the A-EPDB highlighted by solid border lines are: 1) the SYNCHRO-SYM with at least a simple synchronous modem stage of electronics for the stator AC port and a modified REG module for the rotor speed-synchronized AC port, which inherently includes electronic step-up-down transformers (i.e., the PDF-HFT); 2) the storage or battery module; and 3) the active battery contactor or power module, which is another modified REG module. Additional modules, such as the optional dotted modules, can be added by tapping into the A-EPDB anywhere along its length. Because of the common A-EPDB, all modules are simple and

Figure D



can symmetrically interface with any AC or DC power, such as SYNCHRO-SYM (i.e., dual AC electrical ports) with a DC battery. In a minimal configuration, the high performance A-EPDB of Figure D has two half rated electronic stages for the SYNCHRO-SYM motor and for the SYNCHRO-SYM generator with a normalized total of two full rated stages and one full rated stage for the battery contactor with a combined rating of “three” full rated electronic stages of loss, cost, and size, which is 3/5th the overall complexity, cost, size and electrical loss of the lower performance DC-EPDB. With direct high frequency AC to AC conversion, the bulky, inefficient low frequency reactive components of the DC Link Stage, such as chokes, transformers, and bypass capacitors, are eliminated. Furthermore, the A-EPDB leverages all of the unique characteristics of the high frequency REG, such as: 1) compact and efficient high frequency reactive components, including PDF-HFT with inherent step-up-down transfer ratio; 2) reduced complexity and fewer number of electronic stages; 3) differential gating with inherent soft (resonant) switching to reduce switching losses, component stress, and transmission line effects while providing fast fault detection and correction; 4) open or short detection and de-activation within half cycle periods (20.8 us at 24 kHz) without the effects of traveling or standing waves; 5) tap-able along length to supply any AC or DC power with compact power modules; 6) seamless scalable connection of multiple modified REG (or power modules) with bi-directional power flow; 7) multiphase with inherent fault tolerance to a single AC phase loss with SYNCHRO-SYM technology but with no more copper than the DC-EPDB because power is shared between phases; and 8) etc. Furthermore with seamless synchronous connection, more than one A-EPDB can be introduced in the bus system for redundancy and high reliability with all buses operating during normal conditions to share current and reduce I2R loss. Should any redundant A-EPDB be compromised, the remaining A-EPDB will assume the overall load with acceptably higher loss of the emergency. Not possible with DC, high frequency AC switch-off or switch-on of the A-EPDB occurs on the timely detection of the zero crossing point or soft switching point of voltage or current, which normally occurs every half cycles or 20.8 us at 24 kHz. As a result, only small half-cycle packets of electromagnetic energy are stored or released in the PDF-HFT at any time. Should an open event (i.e., zero current) or a short event (i.e., zero voltage) occur on the A-EPDB, the event absorbs or releases only small half-cycle packets of stored energy at most before power is electronically switched off at the next zero crossing. More importantly, the switching off at zero-crossing of power (i.e., zero voltage or current) mitigates any high frequency traveling or standing wave stress.

d. BEM Advanced EPDB Conceptual Overview Figure E gives a simple block diagram of a Multiphase High Frequency Electrical Power Distribution Bus (A-EPDB), which is a component of the patented SYNCHRO-SYM Technologies. The A-EPDB is between two sets of modified Rotor Excitation Generators (i.e., A&B and C, respectively), which in this case, interface SYNCRO-SYM to a DC or AC power source, such as a battery or multiphase AC of



different phases or frequencies. The HFT electromagnetically isolated the A-EPDB and in accordance with the modified Rotor Excitation Generator (REG), the A-EPDB can be void power switches. Without power switch considerations on the A-EPDB side of the HFT, the A-EPDB can be high voltage but low current (or vice-versa) for lowering copper use, lowering cost or lowering weight through a step-up-step down or multiply stacked voltage leveling HFT winding arrangements. For instance, the A-EPDB could comprise three conductors with each conductor carrying a high frequency carrier signal with the modulation envelope of the appropriate phase according to the conventional low frequency multiphase AC source (e.g., three-phase 60 Hz). The phase envelopes of the A-EPDB can be translated from any DC, Single or Multiphase AC source by the patented actions of the Modified REG C with a very low frequency to minimize the number of poles and diameter of a low speed electric machine application or a high frequency to increase the speed with a minimum number of poles. Clearly, additional SYNCHRO-SYMs with modified REGs of A and B can be tapped into the A-EPDB with an appropriately power rated modified REG of C. However, the cost and efficiency of such a SYNCHRO-SYM arrangement will change. For instance, there are now 72 switches with the arrangement of three Modified REGs, which have a complete stage of electronic switches removed, in contrast to the 48 switches of a (non-modified) REG arrangement. Furthermore, the full power flows through the Modified REG (C) but half the full power flowing through the Modified REG of A and B. Following the same Effective Power Switch Utilization analysis

Multiphase High Frequency Distribution Bus [Tap-able at any point] [High voltage and low current or vice-versa.]

Local motor [REG Controlled low or high voltage bus]

Multiphase or DC Power

A

B

C

B is modified REG with one stage of switches removed from the Distribution Bus side and a long air-gap HFT (lower efficiency) for movement calculation. A and C are a modified REG with one stage of switches removed from the Distribution Bus side and a short or no air-gap stationary HFT, which provides very high efficiency.

SYNCHRO-SYM [For this case]

Figure E



presented, the normalized lost factor will be 24 4*1.73 (or 3.47) for Modified REG A or B (each with one stage of electronic switches) plus 24 2*1.73 (or 6.93) for Modified REG C (with one stage of electronic switches but twice the current or power flow) for a total normalized cost factor based on continuous torque of 3.47+3.47+6.93 (13.9), which is comparable to the power semiconductor cost factor of the DC electric machine system but still considerably less expensive than the PM electric machine system. Following the same Effective Power Switch Loss Factor analysis presented, the normalized voltage drop factor will be 4 2 (or 2) for Modified REG A or B (each with one stage of electronic switches or 4 drops and half the full current flow of the phase), plus 4 for Modified REG C (with one stage of electronic switches or 4 drops at the full current flow of the phase) for a total normalized loss factor of 6 based on continuous torque, which is better than the power semiconductor loss factor of the DC or PM electric machine systems. MULTIPHASE HIGH FREQUENCY ELECTRIC POWER DISTRIBUTION BUS: The inductance per foot of a conductor in free space is about 70 nH and the capacitance per foot is about 30 pf. For a 1000 ft conductor in a high frequency power distribution bus operating at 24 kHz, which is less than one tenth quarter wave length and below the effects of a transmission line. As a result the distributed inductance for the 1000 foot line can be lumped with a lumped inductance of 70 H and a lumped capacitance of 30,000 pf. In comparison, the inductance of the HFT operating at 24 kHz is about 11 mH or 200 times higher than the 1000 foot conductor and the inductive impedance of a large motor operating at 60 Hz is 740 mH or 8000 times larger, both of which are overwhelming in comparison to the lumped inductance of the 1000 foot distribution line. The inductive impedance along the line is 24 x 103 x 2 x 70 x 10-6 11 ohms. The capacitive impedance to ground is 1 ÷ (24 x 103 x 2 x 30,000 x 10-12) 220 ohms. The inductive or capacitive impedances are reactive impedances, which do not dissipate power because current is orthogonal to the voltage but do change the power factor of the line and contribute to voltage drop along the line. Similar to a DC line, there is distributed resistance to ground via the insulation medium, such as air, and in series with the conductor and as a result, the same dissipation and voltage drop occurs, regardless of frequency (even at DC). However, without proper shielding of the distribution conductor (e.g., coaxial cable, etc.), high frequency increases the radiation area by the square of distance from the inductor, which provides a low resistive path and a higher loss. Not possible with DC, the AC line inductance and capacitance can be leveraged in a resonant application to provide a smoother edge turn-off and turn-on of the line power at the zero crossing points (i.e., resonant or soft switching) to avoid destructive or dangerous standing waves. In addition, a high frequency power distribution bus can more easily translate voltages with a compact electronic transformer. Considering the inductance ratio between the 1000 foot line and the HFT, the voltage drop across the HFT (or across the electric machine) dominates. This is important because the reactive impedance of the HFT in the Modified REG allows active filtering



or the soft switching of a pure sinusoidal signal at the current or voltage zero crossing while allowing the full power of the sinusoidal signal to be propagated through the Modified REG to the load or source. In contrast, hard switching would exhibit very fast edges (not slow edges of a sinusoid signal), which results in high harmonic content and standing waves in the long transmission line as discussed. Furthermore, proper power propagation would only occur at the peaks of the sinusoid signal, which results in hyper-sinusoid current signals with low root-mean-square (RMS) content. 7. BEM Proposal and Associated Risks

a. BEM Value Added With significant self-funded resources continually devoted specifically to prototyping, development, CAD design, and promotion of SYNCHRO-SYM technologies, BEM is presently considered a small design house for SYNCHRO-SYM technologies without in-house manufacturing for large sized electric machines. Still, BEM has a seamless path to large scale manufacturing: 1) with the contract leveraging of surplus manufacturing base at present; 2) as keeper and expert of SYNCHRO-SYM technology knowledge base with over 25 years research, development, and prototyping experience, which have been subsequently verified years later by unrelated but comparable concept catch up from the electric machine establishment; 3) with the developed CAD tool for the universal design of axial-flux form-factor, which best accommodates SYNCHRO-SYM technologies; 4) with the simple patent-pending Smart Core Manufacturing Tool (SCMT) for Axial Flux Cores; 5) with the simple patent-pending Power Stacking Technology (PST) that accommodates multiple increases in power rating with a single inventory of components while improving cooling within the same diameter package; 6) with an electronic controller that uses readily available off-the-shelf components arranged in a different but simpler circuit topology than conventional controllers; 7) with the legacy of C-WRDF-EMS template designs readily available from industry and academia establishments; and 8) with the in-house inventory of SYNCHRO-SYM designs and development. Instead of leveraging conventional radial-flux wound-rotor doubly-fed technology from the electric machine industry, BEM is marketing SYNCHRO-SYM technology on its cost-performance merits with the benefits of an axial-flux form-factor as discussed.

b. BEM Technology Assessment Clearly legacy products, designs, and research demonstrate the C-WRDF-EMS is scalable to any power rating but is dependent on the power capacity, real-estate, and efficiency of the slip-ring assembly and the instability of control, particularly when motoring. Inherently brushless, symmetrically stable, and automatically synchronous, SYNCHRO-SYM depends only on the power rating of the proprietary PDF-HFT and the modulation control algorithms that span several technical disciplines in a uniquely innovative way, all of which have been verified by BEM research, development, and prototyping with other seemingly common aspects recently verified by the industrial and academic establishments continually playing catch up over time, such as the successful institutional research, prototyping and commercialization of electronic transformers to replace low frequency AC utility transformers and Variable Frequency Transformers for the flexible AC transmission system (FACTS).



8. APPENDIX I (EMS Design Constraints) All magnetic rotating electric motor or generators have at least one armature (i.e., singly-fed) and at most two armatures (i.e., doubly-fed). By the definition set forth, the armature is an independently excited multiphase winding set that supports bi-directional power flow. The armature of any electric motor or generator must obey the same design relationships:

1. ;sSynchronouDesignAirgap SpeedKVoltage “Faraday’s Law”

2. ;TorqueDesignAirgap CurrentKTorque “Lorentz Relation” (Modified for Torque)

3. ;1 FrequencyP

SpeedP

sSynchronou “Synchronous Speed Relation”

(Rev/Second)

4. ;1 FrequencyP

ASpeedP

eeSpeedRangConstTorqu

5. ;0

DepthAirgapMMF “Ampere Circular Law”

(Modified magnetic path)

6. ;TorqueArmature CurrentVoltagePower

7. ;ArmatureTotalMechanicalElectrical PowerAPowerPowerPower

Combining relations 1, 2, 4, 6 & 7:

8. ;A

PowerFrequency

PTorque ElectricalP

Where:

Airgap - Air-gap Flux Density; [Constrained by the same core saturation properties available to all electric motors or generators]

CurrentTorque - “Active” Current flowing in a single Armature; [Less Loss and Magnetizing Current]

CurrentTotal ;TorqueCurrentA [Assuming both armatures are rated for the same power]



Notes:

For a given armature power rating, torque depends on the Frequency and PP; The Lorentz Relation was modified for a rotating motor or generator by

introducing the circumference term, W; The “Synchronous Speed Relation” gives the ± speed of the rotating magnetic

field for a given frequency of excitation; The “Constant Torque Speed Range” is the maximum speed for a given frequency

of excitation; The Ampere Circular Law describes the flux density, , of the armature or any

winding with a given MMF;

Frequency - Armature Winding Excitation Frequency; [Contrary to descriptive terminology, such as DC electric motor, all electric motors or generators require Alternating Current (AC)]

A - Number of Armatures; [A = 1 (i.e., Singly-Fed) or 2 (i.e., Doubly-Fed)]

KDesign ;KWLNP [The same Design/Fabrication constraints available to all electric motors or generators]

Where: PP - Number of Poles-Pairs;

[So-called Brushless Induction Doubly-fed electric motor or generators have an effective P=(P1+P2)/2, where P1 and P2 are the unlike pole counts on the two armature windings, respectively, to guarantee speed-based induction (i.e., asynchronous) operation]

N - Number of Winding-Turns; L - Length of winding cutting Magnetic Field; W - Circumference of the Armature winding end-turns; K - design constant for slot grouping, etc., which is

virtually the same for all EMS winding sets MMF - ;gMagnetizinCurrentNiveForceMagnetoMot

- CurrentMagnetizing is “Reactive” current; AirgapDepth - The magnetic path length of the airgap.

[Ampere’s Circular Law was modified to confine the magnetic path to the low permeability of the airgap, 0, because of the relatively high permeability of the magnetic steel core]



Without superconductor considerations, air-gap flux density, Airgap, is constrained by the same magnetic saturation properties of the magnetic steel core that is available to all. Regardless of high magnetic energy product, high performance permanent magnets (PM), such as neodymium and samarium-cobalt, have a limited flux density, which is a lower achievable air-gap flux density than what could be provided by winding magneto-motive-force (MMF);

The KDesign parameter, which is the product of P, N, L, and W, determines the physical size of the armature and effectively, the size of the magnetic core and the power rating of the electric motor or generator. The same KDesign parameters are available to all with the same interrelated mechanical constraints. The KDesign parameters are significantly affected by the same slot dimensions, which is where the winding conductors reside. Cooling methods, wire size, materials, etc. are equally available to all electric machines but dramatically differ the dimensional, continuous torque, and continuous power properties between contesting electric machines unless consistently applied!

Upon reviewing the electric motor or generator relationships (1 – 5), the following observations between similarly rated electric motor or generators clearly emerge, which contradict marketing gimmickry:

Voltage is Speed (or vice-versa); Current is Torque (or vice-versa); All electric motor or generators display similar continuous torque or torque density with the same optimized KDesign constant; Only SYNCHRO-SYM (A = 2) has the highest continuous power density because the armatures of a brushless and fully stable wound-rotor [synchronous] doubly-fed electric motor or generator reside on the rotor and stator, respectively, to optimally utilize all electric machine real-estate;

9. APPENDIX II (DC and AC Power Transfer) There are three basic means for electricity distribution, Direct Current (DC), Single Phase Alternating Current (AC) and Multiphase AC with Three Phase AC (i.e., multiphase) the predominant means of electricity distribution. DC Real Power Transfer: DC power is the product of peak current and peak voltage = VPEAK x IPEAK or V*I. Where:

VPEAK: Maximum voltage; IPEAK: Maximum current.

Direct Current (DC) power distribution requires at least two conductors (i.e., neutral and live) to transfer V*I power. The normalized power transfer per conductor (NPTC), which



is Power ÷ Number of Conductors, indicates the efficient use of conductors (e.g., copper utilization). For DC, the NPTC is 1/2 units per conductor. Two Phase AC Real Power Transfer: Single Phase AC power is the product of RMS current x RMS voltage = VRMS x IRMS or V*I/2. Where:

VRMS: Peak Phase Voltage ÷ 2 ; IRMS: Peak Phase Current ÷ 2 .

Single Phase Alternating Current (AC) power distribution requires at least two conductors (i.e., neutral and live) to transfer V*I/2 power. For Single Phase AC, the NPTC is 1/4 units per conductor. Three Phase AC Real Power Transfer: The power transfer for each phase (e.g., single phase) of Three Phase AC power is RMS current x RMS voltage = Vpeak x Ipeak/2 or V*I/2. For all three phases, the Three Phase AC Power transfer is 3*V*I/2 or 1.5V*I.

222PeakPeakPeakPeak

RMSRMSIVIVVIaseRMSPowerPerPh

PeakPeak IVasePowerPerPhRMSPowerTotal233 [for a three phase

system] Similarly, three-phase power at any instance along the sinusoid:

PeakPeak

PeakPeakPeakPeakPeakPeak

PeakPeak

PeakPeak

PeakPeak

IV

IVIVIV

tCosItCosVtCosItCosV

tCosItCosVcePowerIns

23

41

41

)240(240120120

00tan

Three Phase AC power distribution requires at least three conductors to transfer 1.5V*I of power. For Single Phase AC, the NPTC is 1/2 units per conductor, which is equal to the normalized transfer per conductor for DC but twice the normalized transfer per



conductor for Single Phase AC. Three Phase AC efficiently utilizes copper as well as DC power, which is twice the efficient utilization as Single Phase AC. Apparent Power Transfer to a multiphase AC load, such as electric machine: All electric machines require multiphase AC for practical operation, which is the production of smooth average torque. Clearly, multiphase AC power, such as Three Phase AC power is the ideal medium for at least the following reasons: 1) no multiphase conversion process is required, such as single phase AC or DC to multiphase AC, and 2) multiphase AC (or DC) is the most effective method of power transfer and copper utilization. With an AC phase voltage, V, and an phase current, I, across each phase load (in conjunction with power semi-conductors (switches) for power conditioning), Figure F shows the peak power supplied to each load of the three phase configuration is 1.5 V*I but the peak Apparent Power is 1.73 V*I. In contrast, the DC source would have to raise its voltage (or current) by 1.73 to supply the same power to the multiphase AC load (e.g., electric machine) after conversion to multiphase AC; otherwise, DC power with V*I rating could only supply the multiphase load with V*I ÷ 1.73 when converted to three phase AC. Raising the voltage or current of the DC source to meet the Apparent Power of a three phase load divides the normalized insulation or conductor carrying capacity by 1.73, which gives the multiphase AC distribution bus a considerable advantage to the normalized power transfers per conductor for supplying a multiphase load.

Electronic Conditioning of DC or AC Power: Some reasonable assumptions about power semiconductors:

For every doubling in voltage or current (i.e., power), the cost of a power semiconductor doubles because the die size, the amount substrate material and the manufacturing cost double; A 50% duty cycle at high frequency doubles the current capacity of the power semiconductor (assuming pulse width < the pulse power rating and the temperature is within Safe Operating Area); A doubling in voltage breakdown rating of a power semiconductor, such as an IGBT, doubles the junction drop (or resistance for a FET) because of thicker substrate; Because of the logarithmic function of the IGBT junction, increasing current rating may increase substrate area but does little to increase junction drop;

Figure F

Power Switches and phase load

V*I1.73V



DC Link capacitors and inductors contribute the major portion of size, loss, and cost of the inverter.

DC Link Stage Power Semiconductor Rating: Figure G shows the relative time phases of a three phase AC system. In a DC Link, there are periods when only one active power semiconductor is on because the phase voltage is at its peak in comparison to the other phases (e.g., three phase system). The maximum voltage is 1.73 (i.e., 3 ) the AC peak voltage of the phase. The cycle period can be calculated by determining the time when the voltage of any two phases is the same as follows:

tCostCos 1200

tSinSintCosCostCos 120120

Figure G



tSintCos 866.05.0

tCostSin577.0

866.05.0

T=30 degrees so a pulse width is 120 deg x 2 (for each polarity of the sinusoidal) =240 deg over a 360 deg cycle for 6 pulse rectifying. PulseTimeOnPerCycle = 2/3 period. In a DC Link Stage, this time period (2/3 cycle in a three phase system) is very long in comparison to the “maximum pulse time” for a power semiconductor (i.e., switch) and accordingly, power semiconductors are always considered to be operating in a continuous duty cycle in inverter. Under a DC Link system the power semiconductor junctions are on (continuous duty) at the Peak-to-Peak Voltage (1.73 Peak Phase voltage for three phase system). The Total 3-phase power must be supported by the DC Link Stage:

PeakPeak IVRMSPowerTotal23

The peak (i.e., Peak-to-Peak 3-phase Voltage) voltage across the DC Link Stage is:

PeakVageDCLinkVolt 3 The Rectifiers (and active switches driving the electric machine) for each phase are on for 2/3 cycle, which is considered continuous duty (see analysis). The peak power is shared

between all phases with each phase supplying 2

PeakPeak IV RMS but one switch is “on” (at

a given time) and must pass the absolute peak DC current with the other two switches on the same side of the inverter “off.” Two switches on the other side of the inverter are on at partial peak current (see Figure G). The Power semiconductor must support the following current levels to establish IPeak per AC phase in the electric machine:

PeakPeakDCPeakPeak IVnPerCyclePulseTimeOIV23)(3

PeakDCPeak InPerCyclePulseTimeO

I)(

13

123

PeakPeak IICurrentDCLinkPeak 3.123

31

23



Electronic conditioning of the DC Link Stage of a three phase AC system requires power semiconductors rated at [1.3 x Peak AC Current or 1.3*IPeak] and [1.73 Peak AC Voltage or 1.73*VPeak]. Effectively, the Power Semiconductors must have a power rating of 2.25* VPeak*IPeak of the AC Phase Power. The DC Link Stage can incorporate active filtering, which reduces the cost, size, and loss of the DC Link Stage but complicates the circuitry with more active components rated for the power of the DC Link Stage. REG AC to AC Power Semiconductor Rating: The REG electronically conditions each phase independently, while smoothly and evenly distributing the power across the phase sinusoidal wave with virtually no harmonic content. Furthermore, the bipolar power semiconductors switch on and off at high frequency (for the HFRT) with a duty cycle that is well within the peak pulse width rating of the power semiconductor or a truly 50% duty cycle (assuming temperature is kept within the Safe Operating Area). Power Semiconductor data sheets show a maximum IPulse capacity with a 50% duty cycle. Furthermore, at a 50% duty cycle, the junction temperature is reduced for lower junction voltage or resistance (that will not be considered). If the comparison is comparing REG controlling SYNCHRO-SYM (i.e., doubly-fed) to an FOC control singly-fed electric machine, the REG controls only half the power for another factor advantage of 2. Electronic conditioning of the direct AC-to-AC method of the REG requires power semiconductor rated for [Phase Peak Voltage or VPeak] and with the 50% duty cycle rating for current [Phase Peak Current/2 or IPeak/2]. REG versus DC Link Stage Cost Factor: REG power semiconductors have a 2*2*1.73*1.3 or 9 cost factor advantage over the DC Link Stage power semiconductors, if comparing SYNCHRO-SYM to Singly-fed FOC. 2 advantage for half power rated controller, 2 advantage for half duty cycle operation at switching frequency, and 1.73 advantage for phase voltage (not phase-to-phase voltage of a DC Link stage). REG power semiconductors have a 2*1.73*1.3 or 4.5 cost factor advantage over the DC Link Stage power semiconductors, if comparing SYNCHRO-SYM to Wound-Rotor Doubly-fed under today’s state of art Field Oriented Controller (FOC). Cost and Electrical Loss Study between the REG and the Field Oriented Control (FOC) DC Link Stage: The study neglects the cost and loss of the large reactive components (e.g., capacitors and chokes) of the FOC DC Link Stage and the high frequency reactive components of the



REG HFRT. However, studies show the reactive components of the DC Link Stage exhibits the major portion of the loss and cost (and size) of the FOC electronic controller compared to high frequency components. Furthermore, this cost and loss study only concerns the linear regions of the power semiconductors and does not concern switching losses. Generally, FOC controllers use hard switching methods, which show high switching losses. The REG has inherent soft switching (e.g., always zero crossing signals), which has negligible switching losses. COST: The REG has 48 power semiconductors (with VPeak and IPeak ratings with duty cycle at 50%) for a full bridge configuration or 24 power semiconductors (with VPeak and IPeak ratings with duty cycle at 50%) for a push-pull configuration. In contrast, the FOC has 12 power semiconductors (without active filtering). It was previously shown that the REG for SYNCHRO-SYM (i.e., doubly-fed) has a 9 cost advantage over FOC singly-fed electric machines. The REG ÷ FOC cost factor is (48 ÷ 9) ÷ (12) = 0.44 or the cost of the REG semiconductors is 1/3 (30%) of the cost of the FOC semiconductors for the same power rated electric machine (SYNCHRO-SYM versus singly-fed FOC electric machine). The cost of the capacitor bank of the DC Link Stage (with the largest capacitor and smallest choke as optimally designed for highest efficiency) is 110-120% of the drive cost.2 Electrical LOSS: The REG has the electrical loss of 8 junction drops plus the HFRT for a full bridge configuration or 4 junction drops plus the HFRT for a push-pull configuration. The FOC has the electrical loss of 4 junction drops plus the DC Link Stage. The REG of SYNCHRO-SYM supports half the power and an effective current of 1/1.3 of the FOC singly-fed electric machine for a loss factor of 2.6. The REG ÷ FOC electrical loss factor is (8 ÷ 2.6) ÷ (4) = 0.8 or the loss of the REG semiconductors is 80% of the loss of the FOC semiconductors for the same power rated electric machine (SYNCHRO-SYM versus singly-fed FOC electric machine).

REG

advantage factor

Reasonable Assumptions

DCPeakVoltage 1.73 For every doubling in Peak Voltage

2 Ajith. H. Wijenayake et al, Modeling and Analysis of DC Link Bus Capacitor and Inductor Heating Effects on AC Drives,” IEEE Industry Application Society Annual Meeting, New Orleans, Louisiana, October 5-9, 1997.



Rating of the power semiconductor, the cost doubles, the “Junction Drop” doubles because the substrate is thicker to resist the breakdown voltage, and the Loss doubles (i.e., Junction Drop x Current).

DCPeakCurrent 1.3 For every doubling in Peak Current Rating of the power semiconductor, the cost doubles because the area of the substrate doubles and the Loss doubles (i.e., Junction Drop x Current).

PeakPowerRating 2 For Every doubling for the Peak Power Rating of the Power Semiconductor, the cost and loss double.

DutyCycle 2 (1÷Duty Cycle). The duty cycle is the percentage of time the power semiconductor is on. The REG operates at a true 50% duty cycle (bipolar) at high switching frequencies. Operating Temperature is reduced and maximum Pulse current can be the rating, assuming within the safe operating are (SOA) of the semiconductor

Power Semiconductor cost formula for FOC with DC Link Stage Versus SYNCHRO-SYM:

ntSYMSemiCouSYNCHROntFOCSemiCouDutyCycleatingPeakPowerRentDCPeakCurrDCPeakVolt

or

ntSYMSemiCouSYNCHROntFOCSemiCou223.173.1

Power Semiconductor loss formula for FOC with DC Link Stage Versus SYNCHRO-SYM:

psSYMSemiDroSYNCHROpsFOCSemiDroatingPeakPowerRentDCPeakCurrDCPeakVolt or

psSYMSemiDroSYNCHROpsFOCSemiDro23.173.1

10. APPENDIX III (Bibliography of Professional Publications)



The following references from technical professional publications of electric machine research highlight the known attributes of the C-WRDF-EMS.

a. Power Density Attribute of Wound-Rotor Doubly-Fed EMS “Recently, it has been shown that a grid-connected wound-rotor [doubly-fed induction] motor with current injection on the rotor side can be operated in super synchronous mode to produce up to two times the rated nominal power” [See page 1089, Column 2, Paragraph 1] i “Since the full torque can be obtained up to twice rated speed, the power output (of the doubly-fed electric machine), can be up to twice the rating of the machine.” [See page 1329, Column 2, Paragraph 3] ii “Simulation and experimental results are presented from a 50-hp drive, demonstrating that the drive can deliver full torque from 0 to 2-p.u. [twice rated power]” [See Abstract] ii

b. Torque Density Attribute of Wound-Rotor Doubly-Fed EMS “The double armature machine has operating characteristics which make it a desirable energy converter in a drive system. Its continuous power rating is double that normally associated with a given frame size; in addition, it has a maximum pull-out torque of approximately eight times nominal frame size torque rating.” [See page 526, Column 2, Paragraph 1] vi “In particular, the double-speed doubly fed machine is examined in some detail, and it is shown theoretically that the peak-power capability of this machine when acting as a motor is greater than that of any comparable form of machine.” [See Abstract] iii

c. Electronic Controller Attributes of Wound-Rotor Doubly-Fed EMS “ ..each inverter rated for 1 p.u. [1/2 power rating] is capable of producing rated torque at rated frequency….Thus, the motor output power becomes twice the rated power.” [See page 1093, Column 2, Paragraph 1] i "The rating of the power converters used in the rotor circuit [of the doubly-fed motor] is substantially lower than the machine rating and is decided by the range of operating speed [around synchronous speed]." iv

d. Slip-ring Limitation of Conventional Wound-Rotor Doubly-Fed EMS “The higher cost of the machine [due to the slip rings of the Doubly-fed machine] is compensated by a reduction in the sizing of the power converters (of the Doubly-Fed Machine).” [See page 414, Column 2, Paragraph 3] v

e. Stability Limitation of Conventional Wound-Rotor Doubly-Fed EMS “At very low rotor flux frequency [synchronous speed for the doubly-fed or zero speed for the singly-fed], it is very difficult to maintain the rotor [flux] constant…At



very low stator frequency, the DTC algorithm also fails due to …inaccurate estimation of the stator resistance drop” [See page 1333, Column 2, Paragraph 2] ii The problem of inherent instability [hunting] uncontrollable torque angle is an old one … the problem of accelerating the machine and synchronizing it to the power system has continued. [See page 526, Column 2, Paragraph 2] vi Synchronous electric machines and electric machine systems are subject to oscillatory behavior similar to that associated with a simple spring-mass mechanical system. These oscillations occur because the principle torque produced by the machine is proportional to a position variable. Thus, the motion is approximately characterized by a second order differential equation in which the dominant terms are the inertial torque and the position-dependent (synchronizing) torque. [See page 652, Paragraph 1] vii Another interesting and potentially useful device in which the absence of proper damping torques creates a stability problem is the doubly-fed synchronous machine. The velocity dependent torques produced during hunting in this machine are in a direction to increase the oscillation and render the machine unstable. Unfortunately, the conditions which allow full advantage to be derived from the possibility of delivering energy to both the rotor and stator (reduced frame size for a given output at twice normal synchronous speed) are the same conditions which create unstable operation. Thus the desirable steady-state features of this machine are not available because of the stability problems. [See page 652 paragraph 2]vii Two stabilizing control strategies have been proposed…the minimum time sub-optimal control has been found to be superior. [See page 799 Abstract]…Since realization of such a control which requires…zero time is almost impossible, the sub-optimal scheme… is used. [See page 803 paragraph 6] viii The operation of an ideal control circuit would be independent of the amplitude and frequency of the input signal. [See page 656 3rd column paragraph 1]vii

f. Neodymium-Dysprosium Permanent Magnet Cartel Any web search for Neodymium or Dysprosium (i.e., doping agent) will find many articles that detail the global uncertainty and serious nature of the Chinese PM cartel.ix

g. Motor Efficiency Deadlines For European Union Are you ready for Dec. 19, 2010, the next major U.S. motor efficiency compliance deadline?x

h. Electric Machine Core Loss Core Loss Testing.xi

i. Comparable Emerging Technologies Comparable Emerging Technologies. xii,xiii



i “Sensorless Field-Oriented Control for Double-Inverter-Fed Wound-Rotor Induction Motor Drive,” Gautam Poddar and V. T. Ranganathan, IEEE Transactions On Industrial Electronics, VOL. 51, NO. 5, October 2004, pp. 1089-1096. http://ieeexplore.ieee.org/xpl/periodicals.jsp ii “Direct Torque and Frequency Control of Double-Inverter-Fed Slip-Ring Induction Motor Drive,” Gautam Poddar and V. T. Ranganathan, VOL. 51, NO. 6, December 2004, pp 1329-1337. http://ieeexplore.ieee.org/xpl/periodicals.jsp iii Bird, B.M. Burbidge, R.F., Analysis of doubly fed slip-ring machines, Proceedings of Institution of Electrical Engineers, Volume: 113, Issue: 6, June, 1966, pp.1016-1020. iv Rajib Datta and V.T. Ranganathan, "A Simple Position-Sensorless Algorithm for Rotor-Side Field-Oriented Control of Wound-Rotor Induction Machines," IEEE Transactions On Industrial Electronics, Vol. 48, No. 4, August, 2001, pp. 786-793. v “Variable-Speed Wind Power Generation Using Doubly Fed Wound Rotor Induction Machine – A Comparison With Alternative Schemes,” Rjib Datta and V. T. Ranganathan, IEEE Transactions On Energy Conversion, VOL. 17, NO. 3, September 2002, pp. 414-421. http://ieeexplore.ieee.org/xpl/periodicals.jsp vi Norbert L. Schmitz and Willis F. Long, “The Cycloconverter driven Doubly-fed Induction Motor,” IEEE Transactions on Power Apparatus And Systems, Vol. PAS-90, No. 2, March/April 1971, pp. 526-531. vii D. W. Novotny and N. L. Schmitz, “Parametric Pump-Down of Synchronous Machine Oscillations,” AIEE Great Lakes District Meeting, Fort Wayne, Ind., April 25-27, 1962. Page 652-657. viii A.H.M.A Rahim, “Stabilizing Controls for Doubly Fed Synchronous-Induction Machines,” IEEE Transactions on Energy Conversion, Vol. 3, No. 4, December, 1988, pp. 799-803. ix http://rareearthinvestingnews.com/754/us-rare-earths-report-tackles-chinese-monopoly, x http://www.controleng.com/index.php?id=483&cHash=081010&tx_ttnews[tt_news]=40011; http://online.wsj.com/article/SB10001424052748703583404576080213245888864.html?KEYWORDS=Toyota+tries+to+break+reliance+on+china xi Chuck Yung and Travis Griffith, “Core Loss Testing,” IEEE Industry Applications Magazine, Vol. 17, No. 1, January | February 2011, pp. 57-64. xii Jerome Legranger, Guy Friedrich, Stephane Vivier, Jean Claude Mipo, “Design of a Brushless Rotor Supply For a Wound Synchronous Machine For Integrated Starter Generator,” Proceeding 2007 IEEE Vehicle Power and Propulsion Conference, pp. 236-241. xiii M. Ruviaro, F. Runcos, N. Sadowski, I.M. Borges, “Design and Analysis of a Brushless Doubly Fed Induction Machine with Rotary Transformer,” XIX International Conference on Electrical Machines – ICEM 2010, Rome.

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