Advanced Uniterruptible Power Supply Systems

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Advanced Uninterruptible PowerSupply Systems

1 March 2002

Har Hotzvim Industrial Park, 14 Professor Hartum St., Jerusalem 97774, Israel

P.O.B 45029, Tel: +972 (0)2 5888222, Fax: +972 (0)2 5828875

www.gamatronic.com email: info.gamatronic.co.il


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2 March 2002

Contents Table

CONTENTS TABLE ....................................................................................................... 2

1. INTERRUPTION TO THE SUPPLY OF ELECTRICITY............................3

1.1 COMMON MODE NOISE........................................................................... 3

1. 2 DIFFERENTIAL MODE NOISE ........................................................................... 52. TYPES OF UPS SYSTEMS................................................................................6

3. TRUE ON-LINE UPS WITH ON-LINE BATTERIES (GAMATRONIC

TOPOLOGY) ...............................................................................................................7

3.1 CONNECTION OF ON-LINEBATTERIES ........................................................... 7

3.2 RESONANCE CONVERTER RECTIFIER/CHARGER............................................. 83.3 ISOLATION OUTPUT TRANSFORMER ............................................................... 8

4. ON-LINE H.F. UPS SYSTEM, MODEL 1........................................................9

4.1 BATTERIES CONNECTED OFF-LINE WITH RELAY........................................... 94.2 SEPARATESMALL CHARGER FOR BATTERIES ................................................ 94.3 ISOLATION BETWEENINPUT ANDOUTPUT....................................................104.4 ABSENCE OF OUTPUT TRANSFORMER .......................................................... 104.5 MULTI-COMPONENT AND MULTI ENERGY CONVERSIONS............................ 10

5. NON-ISOLATED ON-LINE H.F. UPS SYSTEM, MODEL2(WITHSHARED NEUTRAL LINE TO INPUT AND OUTPUT) ............................................ 11

5.1 BATTERIES CONNECTEDOFF-LINE WITH RELAYS ........................................115.2 SEPARATECHARGER FOR BATTERIES .......................................................... 125.3 ABSENCE OF ISOLATION BETWEEN INPUT AND OUTPUT...............................12

5.4 ABSENCE OF OUTPUT TRANSFORMER .......................................................... 125.5 MULTI-COMPONENTSYSTEM....................................................................... 12

6. THREE PHASE UPS DOUBLE CONVERSION WITH O N-LINEBATTERIES - GAMATRONIC TOPOLOGY...................................................... 13

6.1 ADVANTAGES...............................................................................................13

6.2 DISADVANTAGES .........................................................................................14

7. THREE-PHASE STAND-BY BATTERY UPS WITH ECONOMY MODE -

MODEL3.................................................................................................................... 15

7.1 ADVANTAGES OF ECONOMY MODE..............................................................157.2 DISADVANTAGES OF ECONOMY MODE ........................................................15

7.3 DISADVANTAGES OF NORMAL MODE...........................................................16

8. INCREASING UPS SYSTEMS RELIABILITY ........................................... 17

9. COMPARISON TABLE FOR VOLTAGE RELIABILITY - MTBF... 19

10. CONCLUSION ............................................................................................. 20


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3 March 2002

1. INTERRUPTION TO THE SUPPLY OFELECTRICITY

The supply of continuous, uninterrupted, electrical power to communication andinformation based technologies has become a critical element to their success in

todays business climate. These systems rely on a continuous, undisturbed,electricity supply at all times. Unfortunately, many electrical power generators

throughout the world are unable to guarantee a continuous, undisturbed, supply ofelectricity.

Disturbances in the supply of electricity from a network can take many forms.

Continuous variations to incoming power by way of fluctuations between

high and low voltages. These variations in voltage may frequently extend beyondthe accepted voltage limits demanded by the system they are required to power.

Noise, known as Common Mode Noise, appears in the zero line due to stray

currents. These stray currents are to be found in almost all network generated

electrical power supplies.

1.1 COMMON MODE NOISE

1.1.1 The Common Mode Noise (C.M Noise) phenomenon is illustrated in

diagram (Fig. 1).

Junction 2 is grounded to the earth 3, forming a zero potentialdifference between the earth and zero line. Different current loads resulting

from Za, create a voltage between junction 5 and junction 2, i.e., between (inthis example) a computers zero line and the earth.

In this situation, the zero line 5 has a different potential to that of the

earth even though the supply voltage to the computer between junctions 4 to 5may be completely clean.

It is usually only low voltage (several volts) but may increase to tensof volts due to poor or loose terminal connections. Unstable earth connections

or an under sized conductor may cause these problems which can be solvedonly by the meticulous attention to detail during installation. However, theinstallation of a regular isolation transformer will solve the problem

immediately.

After installing the T2 isolation transformer to the computer, the

voltage between junctions 4 and 5 is transferred, in an isolated manner, tojunctions 7 and 8. Junction 8 is connected to a clean earth line at junction 6.This results in a zero voltage difference between the new zero line (8) and the

earth, effectively cancelling the affects of C.M. Noise from the computer.

An isolation transformer will perform the above operation; yet, it willalso cause a drop in voltage of between 3% - 7% from the networks supplyvoltage.


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4 March 2002

Za

Za

T1

2

4

5

6

1

7

8

T2

Additionalloads

Computer

Line

phase

Neutral

Earth

Mains

Figure 1:Common Mode Noise

1.1.2 Another cause of common mode noise are currents found in the zeroline. These currents, in non-linear loads, possess high harmonic noise.

Within three-phase linear symmetrical loads, currents in each of thephases are at 120 and drop to zero at the zero line. When the loads are non-linear, currents are formed in the higher harmonic noises. These currents are

not moved in a 120 phase; thus, they do not fall to zero, but are accumulated.As a result, higher zero currents are formed.

These high zero currents cause several unwanted effects. These

include conducting lines, fuses and switches assemblies and to overheat,leading ultimately to the zero conductor to disconnect. Any disconnection to

the zero line will cause irregularities in the phase voltages.

Even when the zero line is not disconnected, zero currents will leadto the formation of voltages on the zero line connection to the earth.

Figure 2: Currents in a Three-Phase System


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5 March 2002

1. 2 Differential Mode Noise

Interference on the sinusoidal wave is known asDifferential Mode Noise

(Differential Noise). Diagram (Fig. 3) demonstrates how this type of interference iscreated.

The voltage between junctions 1 and 2 maybe reasonably clean. Junctions 3 and 4show the voltage as it appears to the computer when interference from differentialnoise, caused by thousands of users simultaneously taking power from the same

network, are present. The waves shape becomes distorted due to the impedance Zapresent in the mains.

These users are usually scattered over a geographical radius of many kilometers,and therefore beyond any control.

In addition to the types of interference already mentioned, consumers operating

on the Zb computer line can cause further interference. Use of the isolationtransformer does not solve the problems: the interferences are passed on because the

transformer relays every signal exactly in the same form that it had entered thetransformer. (This is the fundamental definition of a transformer).

Thousands of consumers

6 8

Zb

4

Za1

2

~

due to Zb

Za Zb

Additional system operatingin close proximity to the

computer causing additionaldisturbances due to Zb

53 7

transformer

Computer

cause a voltage drop

Isolation

Figure 3: Differential Mode Noise


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6 March 2002

2. TYPES OF UPS SYSTEMS

There are three accepted types ofUninterruptible Power Supply systems (UPS):

On-Line UPS with On-Line Batteries

On-Line UPS with Stand-By Batteries Line-Interactive UPS

IEC standard 146-4 defines continuity of load power very clearly: voltage to the loadmust continue within voltage and frequency limits when changes in the input and load

occur. The main idea is that nothing should stop this process of continuity. The onlyUPS system that completely fulfills this fundamental requirement is a Double

Conversion On-Line System, complete with On-Line Batteries.

In a Double Conversion On-Line system, the batteries are directly connected to thechargers output and inverters input. In view of the highly competitive nature of the

UPS market and the constant drive toward lower pricing , UPS systems are frequentlydescribed, somewhat falsely, as being On-Line, when they are most certainly not. The

overall build quality, performance and reliability of many UPS systems in themarketplace has dropped considerably with the result that, many UPS systems do notlive up to the customers expectations. This deterioration in performance and quality

is at the cost of some manufacturers ignoring accepted industry standards coveringUPS systems. The most important standard governing the manufacture of any true

On-Line UPS is IEC standard 146-6. This standard defines an On-Line UPS as onehaving a rectifier shared by both the units inbuilt battery and inverter. This is thetrue On-Line Batteries System.

There is also a definition of a UPS with a separate charger for the systems batteries.This is the On-Line UPS with Stand-By Battery System. The batteries are activated by

a contactor or thyristor. This type of UPS, based on a separate charger, often uses a

charger that is only capable of slowly charging the systems batteries. Due to thechargers inherently small size, it is incapable of charging large batteries, which

would be required to achieve a longer back-up time. The charger will also beincapable of completely charging a system's batteries if frequent power failures exist.

To the best of our knowledge, Gamatronics UPSs are the only UPS systemsavailable in todays commercial marketplace which meet the demands of IECstandard 146-6. The On-Line UPS with On-Line Batteries topology today.

A third design of UPS is that known as, a Line-Interactive UPS.


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7 March 2002

3. TRUE ON-LINE UPS WITH ON-LINEBATTERIES (GAMATRONIC TOPOLOGY)

The system has four major characteristic features:

Back-up batteries are permanently connected On-Line between arectifier/charger and inverter (Fig. 4).

Resonance converter technology in the rectifier/charger provides highfrequency conversion coupled with P.F at the input stage.

PWM inverter with an isolation transformer at the output.

Double isolation at the input and output of the unit. The batteries are isolated

from high voltage and allow contact (in the batteries) while increasing back-up

time by external batteries. These systems conform the safety standards dictated byIEC107 health Standard for hospitals and operating theatres.

Figure 4: Double Conversion UPS with On-Line Batteries

3.1 Connection of On-Line Batteries

3.1.1 Batteries are activated without switching or delay.

3.1.2 During power failure, a single efficient energy conversion takes placethrough the inverter, thus utilizing all the batterys energy and ensuring themaximum back-up time possible.

3.1.3 The high power rectifier/charger supplies current to the inverter andbatteries, therefore, it is not necessary to purchase an additional charger.

When the UPS is not fully loaded, large external batteries can beconnected, thus allowing optimal utilization of the powerful chargers ability,This is not possible with small-dedicated chargers.


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3.2 Resonance Converter Rectifier/Charger

3.2.1 Highly efficient due to the high frequencies and soft switching

incorporated within this technology.

3.2.2 High input P.F (using the minimum components), this leading to a

marked reduction in input currents.

3.2.3 Optimum charging for all types of batteries.

3.2.4 Increases in the input voltage range (up to 150 VAC in the lower

range).

3.2.5 Allows for connection to all networks and all input frequencies.

3.2.6 Rapid charging of the existing batteries, as well as of larger batteries,which may be incorporated into the system for longer back-up periods.

3.3 Isolation Output Transformer

3.3.1 Prevents conflict and interference from the inverters output to load.3.3.2 Disconnects a noisy zero line from the input to output (There is

galvanic isolation between the input and output stages).

3.3.3 Allows convenient connection of the zero line to an appropriate earth

line at the output.

3.3.4 Eliminates all DC current at the output (the transformer cannottransfer a DC current, which can cause irreversible damage to the load).

3.3.5 The inverters topology allows unlimited activation of all load types,i.e., active and reactive. .

3.3.6 Allows a balanced output supply if required.

3.3.7 Allows a floating output to ships and hospitals.


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9 March 2002

4. ON-LINE H.F. UPS SYSTEM, MODEL 1

The system has five characteristics (Fig. 5):

The batteries are not permanently connected to the system but remain Off-Line until they become re-connected should a power failure occur. A relay is the

most commonly used method of achieving connection to the system. This type ofUPS system features:

Small separate battery charger.

Total isolation between the input and the output stages.

Absence of an output isolation transformer.

Multi-component use resulting in multi, non-efficient, energy conversion.

Boost

DC/DC Converter InverterRectifier

Small Charger

Input

Batteriesfor backup

Relay

Boost

Output

Normal mode

Backup mode

Figure 5: On Line H.F. Ups System, Model 1

4.1 Batteries Connected Off-Line with Relay

When a power failure occurs activation of the batteries, by relay, to on-line

status will always result in a period of delay. This is due to the time requiredby the system to assess a power failure has occurred before operating the

relay.

4.2 Separate Small Charger for BatteriesThe batteries charger is small and capable limited charging only. To increasea systems back-up time (by the addition of larger batteries), an expensiveexternal charger will be required. It must be capable of work in harmony with

the systems existing charger. This additional charger makes the total systemboth uneconomical and clumsy.


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10 March 2002

4.3 Isolation between Input and Output

The insulation suppresses the interferences from the input to output stages.

In addition, it permits connecting the zero conductor to the required earthline. The load type is limited.

4.4 Absence of Output Transformer

Should a fault develop in the output inverter, a DC voltage in the load could

occur. This DC voltage is capable of causing irreversible damage to the load.

4.5 Multi-Component and Multi Energy Conversions

There are four power conversions during normal mode. During backup mode,

there are also the same number of conversions. This results in considerableenergy losses causing a considerable decrease in a systems back-up time and

reduction in reliability due to the design inherent in a multi-component

system.

CONCLUSION

The on-line H.F.UPS System model1 functions as a Stand-By system, which is relianton batteries switching.

RECOGNITION SIGN

If the batteries are of voltage - 24V-96V and there is no isolation transformer withinthe system, then in most instances this will be a Stand-By Battery UPS.


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11 March 2002

5. NON-ISOLATED ON-LINE H.F. UPS SYSTEM,MODEL2(WITH SHARED NEUTRAL LINE TO INPUT AND OUTPUT)

Boost

PH

DC/AC

PH

NNSmall Charger

Batteries for backup

Relay

Rectifier

OutputInput

Backup mode

Figure 6: Non -Isolated On Line H.F. UPS System, Model 2 (With a Shared

Zero Line to the Input and Output)

This system has five characteristic features:

Batteries are connected Off-Line with relays.

Separate charger for the batteries (i.e., the system has two chargers).

There is no isolation between the input and output stages. The system has no output transformer. The neutral line is connected between

the input and output stages. (see Fig. 6).

Use of multi-components and multi energy conversion losses.

5.1 Batteries Connected Off-Line with Relays

When a power failure occurs activation of the batteries, by relay, to on-line

status will always result in a period of delay. This is due to the time requiredby the system to assess a power failure has occurred before operating therelay.

There are two parallel energy conversions during backup mode. This resultsin a further reduction in battery efficiency during back-up coupled with areduction of reliability due to the design found in a multi-component system.


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5.2 Separate Charger for Batteries

The separate charger for the batteries incorporates two small chargers capable

of only limited charging. To increase the systems back-up time, an additionaland frequently expensive, external charger will be required. It must also be

capable of working in harmony with the existing charger. Overall, the

separate charger makes a system expensive and uneconomical.

5.3 Absence of Isolation between Input and Output

The output is exposed to interferences from the input via all parts of thesystem, as well as from the shared neutral line. To eliminate this interference

an expensive, external isolation transformer will be necessary in order todiffuse the input interferences.

5.4 Absence of Output Transformer

When there is no transformer, the load is exposed to the existing DC voltageat the output during Normal Mode, as well as during inverters fault. It is not

possible to connect every type of load to this systems output.

5.5 Multi-Component System

The systems efficiency is inherently very slow in both operating modes.There is a double boost in the Normal mode. In the back-up mode, the twochangers are activated, and the boost is doubled. This type of UPS designgreatly impacts on the efficiency of energy conversion resulting in far shorterback-up times.

CONCLUSION

The UPS functions as a Stand-By Batteries UPS due to batteries switching.


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13 March 2002

6. THREE PHASE UPS DOUBLE CONVERSIONWITH ON-LINE BATTERIES - GAMATRONICTOPOLOGY

R

S

T

N

L1

L2

L1

L1L2

L2

C

C

C

Input

TransformerInverter

switchStatic

Output

Rectifier

Figure 7: Gamatronic Double Conversion On-Line Batteries System

The charger has six pulses at the input frequency with additional filters for increasingP.F and reducing harmonic distortion levels at the input. The batteries are connectedat the rectifier/charger output stages and inverters input, so no transfer time or delay

occur in their activation. The 3-phase inverter has three IGBT transistor H bridgeswith an isolation transformer. This system has a separate voltage controller for each

phase at the output stage, thus allowing the load to be extremely non-symmetrical.

6.1 Advantages

6.1.1 The rectifier/charger, batteries and inverter are all galvanicallyconnected resulting in the batteries being permanently connected On-Line.The batteries are activated on line when a failure in the power network

occurs. The batteries do not under any circumstance depend on mainsidentification or relay switching to achieve activation of the system.

6.1.2 Wide-input voltage range.

6.1.3 High P.F. (0.92-0.94).

6.1.4 Low THD (7-15%).

6.1.5 Galvanic isolation at the output permits an earth connection at anydesired point.

6.1.6 A large battery charger provides faster batteries charging times,together with the advantage of being capable of charging large batterieswithout an additional charger.


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6.1.7 Diffusion of noise and interferences in the zero line.

6.2 Disadvantages

Relatively higher weight due to the incorporation of 50Hz transformers.

CONCLUSION

On-Line Batteries provide a high reliability of clean continuous power and offersolutions to overcoming the many problems associated with the delivery of inferior

electrical power from the generating network.

The MTBF reliability of this classic UPS system is 31,000 hours i.e., three and ahalf years. By the simple addition of a static switch to the UPSs output (with a

MTBF of 100h), MTBF reliability of the entire system will increase to 12 years.


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7. THREE-PHASE STAND-BY BATTERY UPSWITH ECONOMY MODE - MODEL3

RST

CCC

R

S

T

N

SR

TInput

G4 G5 G6

N

R

S

T

L

L

LPower supply

Input

Output

Static switch

Charger Inverter

Batteries

G1 G2 G3

Figure 8: Economy Mode System With Three-Phase Stand-By Battery UPS

The system incorporates a high frequency rectifier/charger.

When the batteries are in Stand-By mode, the rectifier forms positive and negative

voltages when connected to the zero line. The UPS operates in two modes:

Economy mode - the output is connected to the mains. This is possible by

either manual or automatic operation. The inbuilt controller decides on theoperation default in normal mains condition, though it is impossible to forecast a

normal mains condition. The user is unable to detect whether or not the output isfed by either the inverter or the mains.

Normal mode.

7.1 Advantages of Economy Mode

High efficiency.

7.2 Disadvantages of Economy Mode

7.2.1 The load is connected to the mains with all the defects of the Stand-

By mode and of connection to the zero line found in the network.

7.2.2 The batteries are always on Stand-By and are only activated upon

network failure and relay activation. There is a great dependence onnumerous factors that eventually result in low reliability: the right detection

of network failure, operation of relay, etc.

7.2.3 Slow battery charging rate due to a small charger being incorporatedwithin the systems design. This also makes it incapable of effectively fully

charging any additional batteries.


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7.2.4 While the batteries are working; inverter efficiency is reducedbecause of the two energy conversions inherent within the system.

7.2.5 Low reliability.

7.3 Disadvantages of Normal Mode

7.3.1 Even during double conversion, the system is at disadvantagebecause of the connection of the zero line between the input and outputstages.

7.3.2 When the static switch is connected to the inverter, the batteriesremain connected in Stand-By mode, with all the associated difficulties found

with the system. In addition, remains the problematical connection of theneutral line to the mains.


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17 March 2002

8. INCREASING UPS SYSTEMS RELIABILITY

On the manufacturers responsibility:

Improved engineering design.

Reduction in the number of critical components within the UPS, thus makingit far easier for the customer to program and to statistically reduces the possibilityof system faults.

Learning by overcoming previous design problems, faults and ongoing fieldexperience of the system.

Expert workmanship and build quality coupled with appropriate final

inspection and the meticulous testing of each UPS prior to dispatch.

Compliance with the various national and international quality standards.

On users responsibility:

Selection of quality accessories and associated components, e.g., the use of batteries

having a fifteen year life.

Selecting a UPS of adequate size to match the anticipated loads and to lower the

strain on the systems components. (The MTBF calculations provided by the UPS

manufacturers are performed under the toughest conditions).

All UPS systems should be installed, where ever possible, in a clean, tidy, air-

conditioned dust free environment. The system should be protected from any forof tampering.

The users correct operation under approved conditions.

To ensure the connection the batteries in parallel sets and to replace all faulty

batteries in the shortest time possible.

The connecting of UPSs in series or in parallel configuration (see fig. 9, 10

following) by a fully competent person.


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18 March 2002

Load

MainsUPS II

UPS I

AS2

AS1

Figure 9: UPS Connected in Series

UPS I

UPS II AS2

AS1

AS3Load

Controller

Mains

Figure 10: UPS Connected in Parallel


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19 March 2002

INPUT

OUTPUT

+ +

A.S

UPS

+ +

UPS

+

INPUTOUTPUT

+

UPS

A.S

INPUT OUTPUT

+

INPUT OUTPUT

+

+

INPUT

UPSOUTPUT

9. COMPARISON TABLE FOR VOLTAGERELIABILITY - MTBF

TOPIC LABEL MTBF

(HOURS)

1. Supply from mains100

2 UPS without Static Switch(STSW), with high cost

batteries

31,000

3.5 years

3 UPS without STSW, with two

sets of low cost batteries in

parallel

41,000

4.5 years

4 UPS with STSW, with two low

sets of cost batteries in parallel142,000

16 years

5

Two UPSs connected in

parallel, with two sets of low

cost batteries in parallel

2.5 510

28 years

6 Two UPSs connected in

series, with two sets of lowcost batteries in parallel

5 510

56 years

Condition: 1. MTBF of electricity 100h 2. MTTR required 24h


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20 March 2002

10. CONCLUSION

Double Conversion On-Line Batteries UPS systems overcome all theelectrical problems presented in section 1. Advanced UPS systems allow a clean,

sinusoidal current to be pulled from the mains, i.e., a high P.Fs and low harmonic

distortions. This topology is available both in single and three-phase systems. The sinusoidal current consumption from the mains neutralizes the current

consumption of the loads connected at the UPSs output. This may be non-symmetrical, non-linear and contain especially high harmonic compositions.

In addition, the three-phase UPS system allows the load current to be equallydivided over the mains inputs even when the output load is not truly symmetrical.

The UPS contains a 50Hz transformer that allows disconnection from the zeroline of the dirty mains and the connection of a clean zero junction to the

appropriate earth line. Disconnection of the zero line from the input to the outputallows formation of floating outputs for special devices such as ships andhospitals.

UPS systems that do not have 50Hz transformers require an external 50Hztransformer supply at either the input or output stage of the UPS. It is not possible

to operate without this external transformer. Therefore, it is far more preferable topurchase a UPS with an integrated insulation transformer as manufactured by

Gamatronic Industries.

How do you know you are buying an Advanced UPS On-Line System with anOn-Line batteries? Perform a simple test on the input and output currents and

then by comparing them using a suitable oscilloscope. If the currents are found tobe identical, then the UPS output is fed from the input.

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