HC Tech Manual

INDEX

SR. NO. TITLE PAGE NO.

1 INTRODUCTION 1

2 GENERAL 2

3 OPERATING PRINCIPLES 5

4 AUTOMATIC VOLTAGE REGULATOR 8

5 SALIENT FEATURES OF STAMFORD 10

ALTERNATORS

6 STANDARD REFERENCE CONDITIONS 11

7 GENERAL COMMENTS ON LOAD CONDITIONS 13

8 SELECTION OF AC GENERATORS FOR 14

DIFFERENT LOAD CONDITIONS

9 PARALLEL OPERATION OF AC GENERATORS 17

10 ALTERNATOR RATINGS 19

11 TECHNICAL PARTICULARS 20

12 GENERAL ARRANGEMENT DRAWINGS 26

1.0 INTRODUCTION

CG NEWAGE ELECTRICAL LTD. is a Joint Venture Company intechnical and financial collaboration between Newage International Ltd.,U.K. and Crompton Greaves Ltd., India. The company is located atAhmednagar in Maharashtra.

Newage International, UK are world leaders in the alternator market.The Stamford range of AC Generators have emerged as the mostdependable ones, and are manufactured in line with internationalstandards and well accepted by the market as a quality product.

Crompton Greaves Ltd. is a highly reputed electrical equipmentmanufacturer in the country having a large network of sales & servicebranches

CG Newage is engaged in the manufacturing of the brushless ACGenerators in the range from 30 KVA to 1250 KVA. These alternatorshave proved themselves in every critical environment, in arduousmarine applications and in vital industries like hospitals,telecommunication, information technology and hotels.

The company strongly believes that quality is a fundamental requisitefor success and is committed to excel. The awards won reflect thecommitment to quality.

1. ISO 9002 certification from BVQI in 19962. Rajiv Gandhi National Quality Award in the Large Scale

Manufacturing Category for year 1996, 2000.3. H.N. Thadani Award for best industrial engineering practices from

IIIE in 1998.

CG Newage is confident of continuing its effort towards producing andsupplying the best of products to its customers making them proudowners of a “ STAMFORD” alternator.

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STAMFORDBRUSHLESS AC GENERATORS

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H C 4 4 4 C 2

GENERATOR TYPE HC

FRAME TYPE

TYPE OF CONTROL SYSTEM

NUMBER OF POLES 2, 4 OR 6

CORE LENGTH

NUMBER OF BEARINGS 1 OR 2

MARINE APPLICATION

H C M 4 3 4 C 2

2.0 GENERAL

2.1 TYPE :

STAMFORD HC4, HC5 & HC6 AC generators are of salient pole, revolving field,brushless, horizontally foot mounted, single/double bearing type. These ac generatorsare available in :

a) SELF EXCITED SELF REGULATED SYSTEMb) SEPARATELY EXCITED SYSTEM (with unique Permanent Magnet generator

Excitation system)

2.2 DESIGNATION

For Industrial Generators :

For Marine Generators :

NOTE : The base machine in a HC444C2, HCM444C2 or HC434C1 is referred as HC4Conly.


2.3 CONSTRUCTION :

2.3.1 STATOR FRAME :

The Stator frame is fabricated steel which has less weight and better aesthetics.It is designed to ensure correct distribution of air flow over the stator core andwindings.

2.3.2 STATOR CORE :

The stator core is made of high quality low content silicon steel stampings withC-4 coating for better welding of core packs. These are oriented 90 deg. after everyone fourth length for better magnetic properties. The slots are skewed to reduce thetooth ripples in the voltage wave form.

2.3.3 STATOR WINDING :

The armature coils are made from dual coated, class 200 copper wire & wound witha 2/3 pitch.

The 2/3rd pitch winding eliminates the effect of triplen harmonics. This reduces thevoltage distortion and increases the capability of the alternator to cope with non-linearloads.

2.3.4 STATOR / ROTOR INSULATION SYSTEM :

The insulation system is class H. Main stator windings are vaccum pressureimpregnated in an unsaturated polyster resin and main rotor windings are wet woundwith epoxy resin. These processes are designed specifically to provide protectionagainst the harsh environment encountered in the generator applications. Resins areselected and developed to provide the high build required for static windings and thehigh mechanical strength required for the rotating components. The rotating componentscan withstand on overspeed of 2250 rpm for three minutes.

2.3.5 ROTOR CORE :

The Rotor core is made of high quality low content silicon steel stampings. The polescarry continuous damper windings to facilitate parallel operation.

2.3.6 END SHIELDS :

End shields are of cast iron construction and are fixed by easily accessible high tensilebolts.

2.3.7 BEARINGS :

The bearings used are of sealed bearing type. The bearing life is 30,000 hours ofoperation and is subject to working conditions and environment. High axial vibration

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from the engine or misalignment of the set will also stress the bearing reducing itslife.

2.3.8 SHAFT :

The shaft is made of high quality grade steel. The shaft is liberally designed foroverload & short-circuit conditions.

2.3.9 THE ROTATING RECTIFIER ASSEMBLY :

The rotating rectifier consists of the rectifier hub made of dough moulding compound,the rectifier fins and the rectifier diodes which is specially designed to withstand thecentrifugal forces during rotation. The surge suppresser fitted across the field ensuresthe protection of the diodes in case of surges.

2.3.10 TERMINALS AND TERMINAL BOX ASSEMBLY :

HC4 & HC5 generators are 3 phase reconnectable with 12 ends brought to theterminals & AVR is fitted on the NDE panel of the terminal box as a standard supply.HC6 generators are 3 phase with 6 ends brought to the terminals.

The terminal box has removable panels for easy access.

2.3.11 ENCLOSURE :

IP23 is standard for all industrial generators. The machine is protected against sprayingwater i.e. water falling as a spray at an angle up to 600 from the vertical shall haveno harmful effect. Air filters are available as an option for all generators at reducedrating (5% de-rate).

2.4 BALANCING :

All generator rotors are dynamically balanced to better than Grade 2.5 (BS 6861 :Part 1) for minimum vibration in operation.

2.5 RADIO INTERFERENCE :

The absence of brush gear and the high quality of AVR design ensure low levels ofinterference with radio transmission. Additional RFI suppression kit can be suppliedif required.

2.6 STEP LOAD CAPABILITY :

Additional function controls of DIP and DWELL are provided to enable the loadacceptance capacity of the generator set to be optimised. The Dip feature is availablein SX421, MX341 & MX321 AVRs & the DWELL feature in MX321 AVR.

The Dip feature helps to reduce the block load coming on the engine & the DWELLintroduces a time delay in the recovery of voltage to allow the engine to have animproved speed recovery.

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3.0 OPERATING PRINCIPLES :

3.1 SELF EXCITED AND SELF REGULATED MACHINES :

I. Here the excitation power is derived from the main output winding. Referring tofigure 1, initially the machine builds up voltage with the help of residual magnetism.

II. The automatic voltage regulator (AVR) will sense this low voltage and compare itwith the ‘set reference’ voltage level and provides such power as is available fromthe main stator winding in order to establish the exciter field.

III. The power from the main output winding is rectified in the AVR and added to residualvoltage level of exciter to produce a greater magnetic field strength. This in turnincreases output voltage from the exciter rotor.

IV. The output from the exciter rotor is rectified by the rotating diodes which adds tothe field strength and increases the output voltage from the main stator.

V. The AVR senses this increase, compares it with the ‘set reference’ and uses theincreased power from the main stator to further increase the exciter field excitationas required.

In this way the main stator voltage is progressively built up until the ‘sensed’ voltageis the same as the ‘set reference’ voltage.

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Power

A.V.R.Sense Output

Set Reference

ExciterField(Stator)

Rotating Diodes

MechanicalRotationalPower Input

Main Stator

Main Field (Rotor)

ExciterRotor(Arma-ture)

Fig. 1 Block Schematic Diagram


3.2 SEPARATELY EXCITED MACHINES

I. In the separately excited system (PMG) there is a separate source of exciter fieldpower from a small permanent magnet field a.c. generator mounted on the sameshaft as the main machine. Hence the machine title is ‘separately excited’

II. The permanent magnet produces an output voltage that is only dependant on speedand is independent of load conditions. This constant output voltage is fed to theexciter field winding through the AVR.

III. By comparing the main output ‘sensed’ voltage with the ‘set reference’ voltage, theAVR decides on the proportion of permanent magnet machine output to rectifyand feed to the exciter field.

IV. The exciter rotor output would then increase, establishing a strong main field andtherefore a marked increase in main output voltage.

V. The AVR senses and compares voltages and adjusts exciter field excitation untildesired output voltage is developed.

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A.V.R.Sense Output

ExciterField(Stator)

Rotating Diodes

MechanicalRotationalPower Input

Main Stator

Main Field (Rotor)

Fig. 2 Block Schematic Diagram

Set Reference

Power

ExciterRotor(Arma-ture)

PermanentMagnetStator

PermanentMagnetField(Rotor)


3.3 ADVANTAGES OF PMG EXCITATION SYSTEM :

1) Better motor starting characteristics with lower transient voltage dips.

2) Ability to sustain short circuit current in the event of fault. This presents circuitbreakers enough time to effect a trip to eliminate the fault and provide betterdiscrimination in the protection of sub-circuits.

3) Since the AVR is supplied from PMG, isolated from alternator output terminals,the harmonic currents from the load are prevented from passing to the AVR. Thisreduces voltage distortion.

4) The process of initial voltage build up is very positive in this system, as residualmagnetism is no longer continually depended upon.

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4.0 AUTOMATIC VOLTAGE REGULATOR

4.1 SALIENT FEATURES OF AVR

1) Fully encapsulated AVR aids to withstand humid and corrosive atmosphereconditions.

2) Typical system response :Field current to 90% - 80 msMachine volts to 97% - 300ms

3) Operating temperature : -400C to +600CStorage temperature : -550C to +800C

4) SX 440, SX460 & SX 421 are used in self excited machines and MX 341 & MX 321are used in Separately Excited Machines.

5) Soft start circuitry is included to provide a smooth controlled build up of generatoroutput voltage

6) Under frequency protection is set at 97% Hz. The light emitting diode (LED)indicator, is lit when the generator is running below 97% Hz.

7) Remote voltage adjustment possible in all the AVR types.

8) It is usually fitted on a panel of the terminal box on anti-vibration mounts. It canalso be separately fitted in a switchboard, if required.

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4.2 AVR CHARACTERISTICS & ACCESSORY SELECTION

CONTROL SX 440 SX 421 MX 341 MX 321

SENSING 2 3 2 3

REGULATION 1% 0.5% 1% 0.5%

PMG _ _ REQD REQD

UFRO YES YES YES YES

ENGINE RELIEF FEATURE _ YES YES YES

OVER EXCITATION PROTECTION _ _ YES YES

ACCESSORIES

HAND TRIMMER YES YES YES YES

DROOP KIT YES YES YES YES

CURRENT LIMITING _ _ _ YES

OVER VOLTAGE CIRCUIT BREAKER _ YES _ YES

MANUAL VOLTAGE REGULATOR _ _ YES YES

POWER FACTOR CONTOLLER YES YES YES YES

DIODE FAILURE DETECTOR YES YES YES YES

EXCITATION LOSS MODULE YES YES YES YES

FREQUENCY DETECTION MODULE _ _ YES YES

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5.0 SALIENT FEATURES OF STAMFORD ALTERNATORS

5.1 ELECTRICAL PERFORMANCE

1) AVR used on the machines is imported from Newage International and is of provendesign, reliability and performance. These are uniquely encapsulated against moisture,sand, salt, humidity and corrosive atmosphere ensuring trouble free operations underthe most demanding conditions. The voltage regulation offered is from 1.5% to 0.5%depending on the type of AVR used.

2) There are 12 output terminals which are reconnectable to provide output from 190volts to 440 volts depending on the requirement .Refer to the factory for supply ofreconnectable links.

3) Transient voltage dips are lower.

4) Wave-form distortion on no-load is less than 1.5% .Total harmonic distortion and thetelephone interference is less than 2%.

5) All stators are wound to 2/3rd pitch, which alongwith PMG excitation system and 3phase rms sensed AVR provides better system performance.

6) Damper winding on poles ensure smooth parallel operation with similar and dissimilarmachines and with the grid. Power factor controller is recommended when balancingwith grid.

7) Liberally rated diodes used in rotating rectifier assembly ensures high reliability.

8) The rotating diodes are protected by a surge suppresser which has the ability to chopthe transients.

5.2 PROCESS

1) Gelcoat application is a standard feature which enhances the mechanical strength ofthe stator overhang and ensures trouble free performance in humid and corrosiveatmosphere.

2) Burr free stamping pack construction and file free winding results in excellent qualityof winding and also better machine life.

3) Hammer free assembly and sealed bearing increase bearing life.

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6.0 STANDARD REFERENCE CONDITIONS

6.1 TEMPREATURE

These alternators are designed for an ambient temperature of 400C For marine andother applications where the ambient temperature is greater than 400C, the alternatorsmust be de-rated to ensure that the actual temperature does not exceed the specifiedmaximum.

Outputs are normally quoted at 40 deg. C. These outputs must be multiplied by thefollowing factors for higher ambient temperatures.

TEMPERATURE MULTIPLIER( 0C)

45 0.9750 0.9455 0.9160 0.88

6.2 ALTITUDE

Above 1000 m the effectiveness of the air is reduced sufficiently to make de-ratingnecessary.

For altitudes above 1000 m outputs must be multiplied by the following factors.

ALTITUDES MULTIPLIER

1,500 0.972,000 0.942,500 0.913,000 0.883,500 0.854,000 0.82

6.3 CLIMATE AND ENVIRONMENT

1) Anti-condensation heaters (SPACE HEATER)Space heaters are recommended in areas of high humidity.Condensation or dew will form on all surfaces which are cooler than ambienttemperature. To avoid this, anti-condensation heaters can be fitted which will ensurethe winding temperature remains a few degrees above the ambient temperature andhence no condensation will form. Note that the anti-condensation heaters should beON only when the set is OFF, and they should be switched off whilst the set is inuse. They can be retrofitted at site.

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2) Air FiltersUnder site conditions where the air may be heavily laden with fine dust or sand westrongly recommend the fitting of inlet air filter. The sizing of these is important toavoid airflow restrictions and advice should be sought from the works.

Recommended deration is 5% for machines fitted with air filters.


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7.0 GENERAL COMMENTS ON LOAD CONDITIONS :

7.1 Where a specification exists for any particular load or installation, it is always advisableto forward a complete copy to the factory for examination. As a result of such anassessment it is sometimes possible to incorporate design changes to provide a moreeconomic machine which still meets the specification.

7.2 There are two basic conditions to check when sizing machines. The steady stateCondition, which is mainly concerned with normal operation of the machine withintemperature rise limits; and the transient condition of the machine voltage deviationswhen suddenly applying high current loads (e.g. during motor starting). It is essentialthat both these conditions are checked as a rating sufficient for the steady statecondition is often not large enough to meet motor starting or voltage dip requirements.


8.0 SELECTION OF AC GENERATORS FORDIFFERENT LOAD APPLICATIONS

The different types of loads encountered by an AC Generator can be broadly classifiedas

a) Linear Loads

b) Motor Loads (part of linear loads,considered separately)

c) Non-linear Loads.

8.1 Linear Loads are characterised by

* Constant load impedance regardless of applied voltage.

* The load current increases proportionately as the voltage increases and decreasesa s

the voltage decreases.

Examples of linear loads are motor, incandescent lighting and heating loads.

8.2 SELECTION OF ALTERNATOR FOR LINEAR LOADS

To select the rating of ac generator for linear loads the maximum connected loadand the base load which is always connected has to be considered. In arriving at atotal load figure it is always wise to select the standard rating larger than thatestimated.This despite the fact that all the loads may not be operating at the sametime and hence a smaller machine could have been selected. Future operatingconditions and future growth are very difficult to estimate. An allowance of 15% to20% excess capacity designed into a set now is a small price to pay compared withthe cost of completely new larger unit that may be required to drive additional loadsin a few years time.

8.3 POWER FACTOR

It is the nature of the applied load that dictates the system power factor.

a) The loads which operate at or very close to unity (1.0)power factor include mostforms of lighting, all heating elements, rectifier and thyristor type loads & all domesticloads which are fractional hp motors (washing machine,refrigerator, etc.)

b) For all remaining load types, some knowledge of operating power factor is required,which for motors depends a great deal on their size and power rating.

Stamford a.c. generators perform satisfactorily at any power factor in the range of 0.8p.f. lag to unity p.f. Operation at leading and lagging power factors (below 0.8)demandsa derate and reference to the factory must be made.

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8.4 MOTOR LOADS

During the starting of an induction motor, a very large current is demanded from thepower source, which is known as the starting or locked rotor current. For sizingalternators which have to cater to motor loads, the following guidelines can be referredto.

METHOD OF STARTING STARTING CURRENTDIRECT ON LINE 6 TIMES MOTOR FULL LOAD CURRENT

If starting current is not given starting kVAis 7.1 X hp rating of the motor.

STAR / DELTA APPROX. 3.5 TIMES MOTOR FULL LOADCURRENT.

ROTOR RESISTANCE 1.5 TO 2 TIMES MOTOR FULL LOADCURRENT.

AUTO TRANSFORMER STARTING

65% Tapping 4 Times motor full load current.80% Tapping 4.8 Times motor full load current.

For motor applications the following information should be furnished :

a) Rating of the motor /motors.

b) Type of motor (slip ring /squirrel cage)

c) Method of starting

d) Rated full load current

e) Starting power factor

f) Any restriction on Transient Voltage Dip? (Details of the same)

g) Frequency of starting.

h) Base load at the time of starting induction motor.

i) Any other load apart from the motor loads?(Details there of)

j) Sequence of starting of motors.

8.5 NONLINEAR LOADS

Over a period of time the loads applied to AC generators have become more complexand more care has to be exercised in the sizing of the generators to ensuresatisfactory performance.

8.6 CHARACTERISTICS OF NON LINEAR LOADS

a) A non linear load is one in which the load current is not proportional to theinstantaneous voltage. Often the load current is not continuous.

b) These are essentially electronic loads such as Computers, UPS equipments andvariable speed motor drives.

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8.7 EFFECTS OF NON LINEAR LOADS

a) Non linear loads generate harmonics in their current waveform which in turn leadsto distortion of the ac generator waveform. Depending upon the degree of voltagewaveform distortion this can lead to instability of the excitation system and impacton other loads being supplied by the generator.

b) Odd order hormonics cause overload of neutral conductors.

8.8 GENERAL GUIDELINES ON DERATION FOR NON LINEAR LOADS

LOADS DERATING FACTOR

a) Fluroscent lighting load No derate required.

b) UPS & Telecom load Non linear load should not exceedcontrolled by a 12 Pulse Thyristor 90% of alternator ratingbridge plus a filter.

c) UPS & Telecom load Non linear load should notcontrolled by 6 Pulse thyristor exceed 66% of alternator ratingbridge plus a filter.

d) UPS & Telecom load Non linear load should notcontrolled by 3 Pulse thyristor exceed 35% of alternator ratingbridge plus a filter.

e) Variable speed 6 pulse Non linear should not exceedthyristor bridge controlled drive. 50% of alternator rating

The above percentage figures are guidelines. There may be a problem with electronicload trying to cope with distorted waveform if distortion levels are unacceptable tothe load.

Better sizing of machine is possible on furnishing following information :

a) Number of system pulses : 3, 6, or 12.

b) Level of current distortion produced by the non-linear load.

c) What is the maximum acceptable level of voltage distortion the Non-linear loadcan accept?

d) Operating voltage and frequency.

e) If Non-linear load power requirement is stated in kW, then some guidance regardingoperating power factor & system efficiency is required to establish the alternatorload.

With the information guidance should be sought from the factory regarding alternator sizingfor compatible equipment operation.

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9.0 PARALLEL OPERATION OF A.C. GENERATORS

9.1 INTRODUCTION AND THEORY

No one aspect of the a.c. generator set operation causes more misunderstanding thanthe parallel operation of two or more a.c.generators.

Parallel Operation may be necessary for the following reasons :

i) To increase the capacity of an existing system.ii) Size and weight may preclude the use of one large unit.iii) Allows non-interuption of the supply when servicing is required.

In order to parallel a.c. generators satisfactorily, certain basic conditions have to bemet. These are as follows :

i) All systems must have the same voltage.ii) All systems must have the same phase rotation.iii) All systems must have the same frequency.iv) All systems must have the same angular phase relationship.v) Systems must share the load with respect to their ratings.

The generator waveform plays a big part if successful operation is to be achievedwhen paralleling with the mains/utility supply or with similar or dissimilar machines.

9.2 INSTRUMENTATION REQUIRED :

An ammeter, a wattmeter, voltmeter, power factor meter, synchroscope and a reversepower relay.

A reverse power relay, although contributing a larger proportion of the instrumentationcost, is essential as any engine shut down, from low oil pressure, over-temperatureetc. will result in other systems motoring the failed set with consequent overload tothe remaining systems.

9.3 GENERAL NOTES :

In Stamford machines, the droop CT is wired in the W-phase and its output droppedacross the burden resistor within the AVR. The droop CT is connected to terminalsS1-S2. The droop can be increased by turning the potentiometer in a clockwisedirection. The burden resistor is connected such that the voltage produced across itadds vectorially with the sensing voltage. SX 440, SX 421, MX 341 & MX 321 aresuitable for parallel operation.

Stable parallel operation and accurate load sharing between no load and full load canonly be obtained when the initial voltage settings and the droop kits are correctlyset up. It is also important that the governor characteristics are similar otherwiseincorrect kW load sharing can result when either increasing or reducing load.

It is essential to have droop CT & SX 440 AVR in the alternator for parallel operation& in the case of PMG machines MX 341 & MX 321 AVR to be used.

Remember : The generator droop kit can control only the kVAr sharing andcirculating current. The sharing of kW load is determined by engine governors.

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9.4 NEUTRAL INTERCONNECTION :

Stamford machine can be paralleled with other make machines but with neutrals notconnected. On the other hand, two Stamford machines with similar winding pitch maybe paralleled successfully with their neutrals linked. If during commissioning, it is foundthat neutral currents are flowing, then this will be a product of the characteristics of theload being supported on the local network. Therefore, neutral interconnections is an issueof system design.

9.5 PARALLELING WITH MAINS:

The mains voltage waveform is very close to a sinewave and has a very few harmonics.To parallel successfully with the neutrals linked, the generator is required to have a goodline-line and line-neutral waveform. With 2/3 pitch the line-neutral waveform is excellentand hence paralleling with mains will have no major problems.

For parallel operation with mains, we recommend our Power Factor Controller. It hasfacility for adjusting the voltage of the generator to the fluctuating mains voltage forsuccessful operation. It also improves the power factor of the system thereby reducingutility charges.

A loss of generator excitation during parallel operation will result in heavy circulatingcurrents. The Stamford Excitation Loss Module monitors the generator AVR outputand signals any sustained interruption to an integral relay to initiate an indication / alarm.

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11.0 FRAME V/S OUTPUT

General Notes :

1) All industrial ratings are 3 ph based on 40 0C ambient temperature 1000 maltitude & 415 V.

2) Marine ratings are available and are based on 50 0C ambient unrestricted use.

3) Please refer to factory for 60 Hz., 1800 rpm machines.

4) For ratings other than these please refer to Factory.

5) Continuous development of our products entitles us to change specificationdetails without notice.

FRAME SIZE KVA

HC4C 210

HC4C 225

HC4C 237.5

HC4C 250

HC4D 275

HC4D 285

HC4E 300

HC4E 320

HC4F 350

HC4F 380

HC5C 400

HC5C 437.5

HC5D 475

HC5D 500

HC5E 520

HC5E 550

HC5E 570

HC5E 600

HC5F 625

HC6W 750

HC6Y 800

HC6Y 900

HC6Y 1000

HCK6Z 1250

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NOTES :

A) THE VOLTAGE REGULATION CLAUSES ARE NOT APPLICABLE FOR NON - LINEARLOAD AND UNBALANCED LOAD CONDITIONS.

B) 10% OVERLOAD AND 50% MOMENTARY OVERLOAD CLAUSE IS AS PER IS 4722.THE VOLTAGE REGULATION AND TEMPERATURE RISE ARE NOR APPLICABLE FORTHIS CONDITION.

C) THESE FIGURES ARE FOR GENERAL GUIDANCE ONLY AND ARE NOT TO BE TAKENFOR INSPECTION AND HENCE FOR ACCEPTANCE OR REJECTION.

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