Indian Standard

ROTATING ELECTRICALMACHINES — SPECIFICATION

( Second Revision)

ICS 621,313-13

0 BIS 2001

BUREAU OF IN DIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARC

NEW DELHI 110002

IS 4722:2001

August 2001 Price Group 8

I/

-- .

Rotating Machinery Sectional Committee, ET 15

FOREWORD

This Indian Standard (Second Revision) was adopted by the Bureau of Indian Standards, after the draft finalizedby the Rotating Machinery Sectional Committee had been approved by the Electrotechnical Division Council.

In the first revision of this standard following contents have been brought out in separate independent standards:

a) Type of duty and classes of ratings assigned to rotating electrical machines covered in IS 12824:1989,and

b) Temperature-rise measurements of rotating electrical machines covered in IS 12802:1989.

In this revision, a number of editorial corrections have been incorporated and in addition, some changes havealso been incorporated based on experience for operation of this standard.

The requirements of rotating electrical machines covered in this standard have been updated in line with currentinternational practices.

While revising this standard, assistance has been derived from the IEC Pub 34(1983) now designated as IEC60034 ‘Rotating electrical machines’, issued by the International Electrotechnical Commission (IEC).

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated, expressing the result of a test, shall be rounded off in accordance with IS 2:1960 ‘Rulesfor rounding off numercial values (revised)’. The number of significant places retained in the rounded off valueshould be the same as that of the specified value in this standard.

/

-

IS 4722:2001

Indian

ROTATINGMACHINES —

Standard

ELECTRICALSPECIFICATION

(Second Revision)

1 SCOPE

1.1 This standard covers requirements for rotatingelectrical machines without distinction of output andvoltage but excluding:

a) Traction equipment, andb) Motors covered by IS 996:1979 ‘Single phase

small ac and universal electric motors (secondrevision)’.

1.1.1 Attention is drawn to certain other standardslisted below which may apply when machines arerequired for particular applications. The rating plateof machines built to comply with these standardsindicate the number of the Indian Standards invoked:

IS No. Title

325:1996 Three-phase induction motors~ourth revision)

2635:1975 DC electric welding generators(second revision)

2972 Textile motors:(Part 1): 1979 Loom motors (/irst revision)

(Part 2): 1979 Card motors (@f revision)

(Part 3): 1979 Spinning frame motors (@revision)

3682:1966 Flameproof ac motors for use inmines

5422:1996 Turbine type generators (/h?

revision)

7538:1996 Three-phase squirrel cage inductionmotors for centrifugal pumps foragricultural application

8151:1976 Single-speed three-phase inductionmotors for driving lifts

9283:1995 Motors for submersible pumpsets

9628:1980 Three-phase induction motors withtype of protection ‘n’

2 REFERENCES

The Indian Standards listed in Annex A are necessaryadjuncts to this standard.

3 TERMINOLOGY

3.0 For the purpose of this standard, the followingdefinitiofis shall apply. The definitions of generalterms used in this standard are given in IS 1885(Part 35).

3.1 Rating

The whole of the numerical values of the electrical andmechanical quantities with their durations. andsequence assigned to the machine by the manufacturerand stated on the rating plate, the machine complyingwith the specified conditions.

3.2 Rated Value

The numerical value of a quantity included in therating.

3.3 Rated Output

The numerical value of the output included in therating.

3.4 Load

All the numerical values of the electrical andmechanical quantities that signify the demand to bemade on a rotating machine by an electrical circuit ora mechanism at a given instant.

3.5 No-Load (Operation)

The state of a machine rotating with zero output power(but under otherwise normal operating conditions).

3.6 Full Load

The highest value of load specified for a machineoperating at rated output.

3.7 Full Load Power

The highest. value of power specified for machineoperating at rated output.

NOTE — This conceptalso appliesto torque,current, speed,ete.

3.8 Rest and De-energized

The complete absence of all movements and of allelectrical supply or mechanical drive.

IS 4722:2001

3.9 Duty 3.18 Cooling

,*.. -u_

.

The statement of the load(s) to which the machine is A method by means of which heat resulting fromsubjected, including, if applicable, starting, electric Iossesoccurnng in a machine is given up first to a

braking, no-load and rest andde-energized periods, primary cocdant by increasing its temperature. Theand including their durations and sequence in time. heated primary coolant may be replaced by a new

3.10 Duty Typecoolant at a lower temperature or may be cooled by asecondary coolant in some form of heat exchanger.

A continuous short time or periodic duty, comprisingone or more loads remaining constant for the durationspecified, or a non-periodic duty in which generallyload and speed vary within the permissible operatingrange.

3.11 Thermal Equilibrium

The state reached when the temperature rises of theseveral parts of the machine do not vary by more than2 K over a period of 1 h.

3.12 Cyclic Duration Factor

The ratio between the period of loading, includingstarting and electric braking, and the duration of dutycycle, expressed as a percentage.

3.13 Locked Rotor Torque

The minimum measured torque which the motordevelops with the rotor locked and rated voltageapplied at rated frequency.

3.14 Locked Rotor Current

The measured steady-state root-mean-square currenttaken from the line with the rotor locked with ratedvoltage and frequency applied.

3.15 Pull-up Torque (of an ac Motor)

The smallest torque which the motor developsbetween zero speed and the speed which correspondsto the breakdown torque when the motor is supplied atthe rated voltage and frequency.

NOTES1 This definition does not apply to those asynchronousmotorsof which the torque continually decreases with increasein speed.

2 This value applies to the usual mean torque characteristicwhich excludes transient effects.

3.16, Breakdown Torque (of an ac Motor)

3.19 Coolant

A medium (liquid or gas) by means of which heat istransferred.

3.20 Primary Coolant

A medium (liquid or gas) which, by being at a lowertemperature than a part of the machine and in contactwith it, removes heat from that part.

3.21 Secondary Coolant

A medium (liquid or gas) which, by being at a lowertemperature than the primary coolant, removes theheat given up by this primary coolant by means of aheat exchanger.

3.22 Direct Cooled (Inner Cooled) Winding

A winding in which the coolant flows through hollowconductors, tubes or channels which form an integralpart of the winding inside the main insulation.

3.23 Indirect Cooled Winding

A winding cooled by any other method than thatof 3.22.

NOTE— In all cases when ‘indirect’ or ‘direct’ is not stated, anindirect cooled winding is implied.

3.24 Supplementary Insulation

An independent insulation applied in addition to thebasic insulation in order to ensure protection againstelectric shock in the event of faihtre of the basicinsulation.

3.25 Moment of Inertia

The (dynamic) moment of inertia of a body about anaxis is the sum (integral) of the products of its masselement and the square of their distances (radii) fromthe axis.

The maximum torque which the motor develops with NOTE — This quantity is designated by the letter symbol J andrated voltage and frequency applied at operating is exrmased in K~m2temperature without an abrupt drop in speed.

.

NOTES3.26 Thermal Equivalent Time Constant

1 The definition does not apply to those asynchronous motors The thermal equivalent time constant is the timeof which the torque continually decreases with increase in speed.

2 This value applies to the usual mean torque characteristicconstant replacing several individual time constants,

which excludes transient effects. which determines approximately the temperature

3.17 Pull-out Torque (of a Synchronous Motor)course in a winding after step-wise current change.

3.27 Encapsulated WindingThe maximum torque which the synchronous motordevelops at operating temperature and at synchronous A winding which is completely enclosed or sealed by

speed with rated voltage, frequency and field current. moulded insulation.

2

3.28 Routine Tests

Tests carried out on each machine to check theessential requirements which are likely to vary duringproduction.

3.29 Type Tests

Tests carried out to prove conformity with therequirements of this standard. These are intended toprove the general quality and design of a given type ofmachine.

4 OPERATING CONDITIONS

4.1 Altitude, Temperature and Coolant

Machines shall be designed for the followingoperating site conditions, unless other conditions arespecified by the purchaser.

4.1.1 Altitude

Height above sea level not exceeding 1000 m.For machines intended for operation on a site wherethe altitude is in excess of 1000 m (see 6.3 ofIS 12802).

4.1.2 Ambient Temperature and Temperature of theCoolant

4.1.2.1 Maximum ambient and coolant temperature

The temperature of the air at operating site (which maybe the primary or the secondary coolant, depending onthe ventilation system of the machine) is subject toseasonal variation, but does not exceed 40°C.

For machines intended for operation on a site wherethe coolant temperature is low, by reason of highaltitude, see 6.3 of IS 12802.

Machines intended for operation with a maximumambient temperature other than 40°C are covered by5.3 of IS 12802.

For machines having water-cooled heat exchangers,the temperature of the water at the intake to the heatexchangers shall not exceed 25°C (see 6.1.4 ofIS 12802).

4.1.2.2 Minimum ambient and coolant temperatures

The minimum temperature of the air at the operatingsite (which may be the primary or the secondarycoolant, depending on the ventilation system of themachine) is–15°C, the machine being installed and inoperation or at rest and de-energized.

This applies to all machines except the following:

a) ac machines with rated outputs exceeding3300 kW (or lcVA) per 1000 r/rein, machineswith rated outputs less than 600 W (or VA) andall machines having a commutator or sleeve

b)

IS 4722:2001

bearings. For these machines the minimumambient temperature is +5”C; andMachines having water as a primary or secon-dary coolant. The minimum ~emperature of thewater and the ambient air is +5”C.

NOTE — If temperatures below those given in this standard areto be expected the manufacturer should be informed of theminimum ambient temperature and it should be specifiedwhether this applies only during transport and storage or alsoafter installation. Temperatures below those given shall be thesubject of an agreement between the manufacturer and thepurchaser.

4.1.2.3 Characteristics of gas used as coolant inhydrogen-cooled machines.

Hydrogen-cooled machines shall be capable ofoperating at a rated output underrated conditions witha coolant containing not less than 95 percent hydrogenby vohtme.

NOTE — For safety reason, the hydrogen content should at alltimes be maintained at 90 percent or more, it being assumed thatthe other gas in the mixture is air.

For calculating efficiency in accordance with IS 4889from tests (excluding machines for traction vehicles),the standard composition of the gaseous mixture shallbe 98 percent hydrogen and 2 percent air by volume,at the specified values of pressure and re-cooledtemperature, unless otherwise agreed between themanufacturer and the purchaser. Windage losses shallbe calculated at the corresponding density.

4.2 Electrical Conditions

4.2.1 Electrical Supply

ac machines within the scope of this standard shall besuitable for three-phase 50 Hz, with voltage derivedfrom the nominal voltages given in IS 12360.

In deriving rated voltages for machines, it is necessaryto take into consideration the differences betweendistribution and utilization system voltages.

NOTE — For large high-voltage ac generators, the voltage maybe selected for optimum performance.

4.2.2 Form and Symmetry of Voltage and Currents

Machines shall be so designed as to be capable ofoperating under the conditions detailed in 4.2.2.1,4.2.2.2 as appropriate (see also 4.2.2.3).

4.2.2.1 In the case of an ac motor, the supply voltageis assumed to be virtually sinusoidal as defined in item(a) below. In the case of a polyphase motor, the supplyvoltages are also assumed to forma virtually balancedsystem as defined in item (b) below. Should the limitsin items (a), and (b), occur simultaneously in serviceat the rated load, this shall not lead to any deleterioustemperature in the motor and it is recommended thatthe excess resulting temperature rise or temperaturerelated to the limits specified in 13.2 should be notmore than 10°C.

3

IS 4722:2001

a)

b)

The voltage is considered to be virtuallysinusoidal. If, when supplying an ac motor atrated load, the waveform is such that the dif-ference between the instantaneous value andthe instantaneous value of the fundamentalcomponent does not exceed 5 percent of theamplitude of the latter;

In temperature-rise testing, as specified inIS 12802 such amplitude difference shall notexceed 2.5 percent.A polyphase voltage system is deemed toform a virtually balanced system of voltagesif the negative sequence component does notexceed 1 percent of the positive-sequencecomponent of the system of voltages over along period, or 1.5 percent for a short periodnot exceeding a few minutes, and if the voltageof the zero-sequence component does notexceed 1 percent of positive-sequence

component.

NOTE — Motors shall be able to operate with a negativesequence component of voltage of 2 percen~ but thismay involve very severe conditions which could affectthe life of motors.

In temperature-rise testing as, specified in IS 12802,negative-sequence component shall be less than 0.5percent of the positive sequence component of thesystem of voltages, the influence of zero-sequencesystem being eliminated. By agreement betweenmanufacturer and purchaser, the negative-sequencecomponent of the system of currents maybe measuredinstead of the negative-sequence component of thevoltages, and this shall not exceed 2.5 percent of thepositive-sequence component of the system ofcurrents.

NOTE — In the vicinity of large single-phase loads (forexample, induction furnaces), and in rural areas particularly onmixed industrial and domestic systems, supplies may bedistorted beyond the limits set out above. Specialarrangements will then be necessary between the manufacturerand purchaser.

4.2.2.2 In the case of an ac generator, the circuit whichit supplies is assumed to be virtually non-deformingand virtually balanced as defined in items (a) and (b)below. Should the limits defined in items (a) and (b)occur simultaneously in service at the rated load, thisshall not lead to any deleterious temperature in thegenerator and it is recommended that the excessresulting temperature rise of temperature related to thelimits specified in Table 1, Table 2 and Table 3 ofIS 12802 should be not more than 10”C.

a) A circuit is considered to be virtually non-deforttiing if, when supplied by a sinusoidal,that is to say, none of the instantaneous valuesdiffer from the instantaneous value of the samephase of the fundamental wave by more than5 percent of the amplitude of the latter.

b) A polyphase circuit is considered to be vir-tually balanced if, when supplied by a balancedsystem of voltage, the system of currents isvirtually balanced, that is to say, neither thenegative-sequence component nor the zero-sequence component exceeds 5 percent ofthe positive sequence component.

4.2.2.3 In the case of a dc motor supplied from a staticpower converter, the pulsating voltage and currentaffect the performance of the machine. Losses andtemperature rise will increase and the communicationis more difficult compared with a dc motor suppliedfrom a pure dc power source.

Thus it is necessary for motors intended for staticconverter supply to be designed to operate under theseconditions and it is often necessary to provide a dcmotor with an external inductance for reducing thepulsation.

In order to obtain a proper combination of dc motorand static power converter, the motor manufacturershould be consulted.

4.3 Voltage and Frequency Variation DuringOperation

4.3.1 Generators complying with these requirementsshall be capable of suppl ying their rated output at ratedspeed (and at rated power factor where separatelycontrollable) at a voltage that may vary between95 percent and 105 percent of their rated voltage.

4.3.2 Motors complying with these requirementsshall be capable of providing their rated output with:

a) The terminal voltage differing from its ratedvalue by not more than * 6 percent, or

b) The frequency differing from its rated value bynot more than i 3 percent, or

c) Any combination of (a) and (b).

In the case of continuous operation at the extremevoltage limits specified above, the temperature-riselimits stated in Table 1 and Table 2 of IS 12802 shallnot exceed by more than:

a) 10°C for machines of outputs up to andincluding 1000 kW (or kVA), and

b) 5° C for machines of outputs exceeding 1000kW ( or kVA).

Motors, when operated at the extreme conditions ofvoltage and frequency variation, may not necessarilyhave their performance specified in the relevantstandard.

NOTE — Machines should not be operated in service at loadsin excess of their rated load or under conditions differing fromthe rated conditions unless it is known that they are suitable forsuch use.

+

/

,’

,,... .

.

4

I

Table 1 Weighting Factors(Clauses 4.2.2.2 and 9.1,2)

Frequency Weighting Frequency WeightingHz Factor Hz Factor

(1)

16.66501001502002503003504004505005506006507007508008509009501000105011001150120012501300135014001450150015501600165017001750

.18001850190019502000

(2) (3)

0.00000117 20500.0000444 21000.001120.006650.02230.05560.1110.1650.2420.3270.4140.5050.5850.6910.7900.8951.0001.101.211.321.401.461.471.491.501.531.551.571.581.601.611.631.651.661.681.70i.711.721.741.751.77

215022002250230023502400—2450250025502600265027002750280028502900295030003100320033tXl34003500360037Mt380039004000410042004300440045004600470048004900

(4)

1.791.811.821.841.861.871.891.90—1.911.931.931.941.951.961.961.971.971.971.971.971.941.891.831.751.651.511.351.191.040.8900.7400.6100.4%0.3960.3160.2320.1990.1380.125

5000 0.100

Table 2 Cross-Sectional Areas of Earth Conductor(Clauses 4.2.2.2 and 12.1.6)

Cross-SectionalArea of t%ss-Seetional Area of thethe Live Condrretor Earth of Protective

mm2 rnrr?(1) (2)4 46 610 1016 1625 2535 2550 2570 3595 50

120 70150 70185 95240 120300 1504txl 185

IS 4722:2001

4.4 Machine Neutral Earthing

4.4.1 ac machine shall be suitable for continuousoperation with the neutral at or near earth potential.They shall also be suitable for operation on unearthedsystems with one line at earth potential for infrequentperiods of short duration; for example, as required fornormal fault clearance. If it is intended to run themachine continuously or for prolonged periods in thiscondition, a machine with a level of insulation suitablefor this condition will be required and the conditionshall be defined in operating instructions.

If the windings do not have the same insulation at theline and the neutral ends, this shall be defined inoperating instructions.

NOTE — The earthhrg of interconnection of machine neutralpoints should not be undertaken without consulting the machinemanufacturers because of the danger of zero-sequencecomponents of currents of all frequencies under some operatingconditions and the possible mechanical damage to the windingdue to line-to-neutral fault conditions.

5 TYPES OF ENCLOSURES

Machines covered by this standard shall have one ofthe degree of protection as given in IS 4691.

6 METHOD OF COOLING

The methods of cooling of rotating electrical machinesand their designations shall be in accordance withIS 6362.

7 ASSIGNMENT OF RATINGS

7.1 The ratings assignment to the electrical machinesshall take into account the class and type of dutycovered in IS 12824 and as marked on the rating plate(see 3.1).

7.2 Preferred Voltages

For the purpose of this standard, the preferred voltageshall be in accordance with IS 12360.

7.2.1 The voltages preferred for three-phase 50 Hzmachines are 415 V, 3.3 kV, 6.6 kV, and 11 kV.

NOTES1 The voltages above 11 kV are subjeet to mutual agreementbetween the manufacturer and the user.2 The coordinationof voltage and output ratings of ac machinesis given in 10.1.

7.3 Frequency and Number of Phases

For ac machines the frequency shall be the standardfrequency of 50 Hz.

7.3.1 The standard number of phases for ac machinesshall be three.

7.4 Preferred Rated Output

The rated output of the various types of rotatingelectrical machines should be assigned in accordancewith IS 12824.

5

I/

IS 4722:2001

Table 3 Overspeed(Clauses 4.2.2.2 and 17.1)

Item Machine TypeNo.(1) (2)1 ac machines:

— All machines except

@

b)

c)

those specified beiow:

Water-turbine drivengenera tors, anyauxiliary machinesconnected directly(electrically ormechanically) to themain machine

Machines which mayunder certaincircumstances bedriven by the load

Series and universalmotors

2 dc machines:

O

b)

c)

d)

Shunt-wound andseparately excitedmotors

Compound-woundmotors having speedregulation of 35percentor less

Compound-woundmotors, having speedregulation greater than35 percent and series-wound motors

Permanent-magnetexcited motors -

e) Generators

OverSpeedRequirements

(3)

1.2 times the maximum ratedspeed

Unless otherwise specified, therunaway speed of the set but notless than 1.2 times the maximumrated speed

The specified runaway speed ofthe set but not less than 1.2 timesthe maximum rated speed

1.1 times the no-load streed atrated voltage. For motorsintegrally attached to loads thatcannot become accidentallydisconnected, the term no-loadspeed shall be interpreted tomean the lightest load conditionpossible with the load

1.2 times the highest rated speedor 1.15 times the correspondingno-load speed, whichever isgreater

1.2 times the highest rated speedor 1.15 times the correspondingno-load speed, whichever isgreater but not exceeding 1.5times the highest rated speed

As per mutual agreementbetween the manufacturer andpurchaser

Overspeeds as spmitied in item2(a), unless the motor has aseries winding and, in such acase, they shall withstand theoverspeeds specified in item 2(b)or 2(c) as appropriate

1.2 times the rated soeed

7.4.1 Preferred Outputs of Motors

The preferred output ratings for dc motors and acinduction motors up to and including 110 kW are:

kW kW kW

0.06 1.1 18.5

0.09 1.5 220.12 2.2 30

0.18 3.7 370.25 5.5 45

0.37 7.5 55

0.55 11 750.75 15 90

110

7.4.2 The output ratings above 110 kW shall followthe R20 series covered in IS 1076.

7.5 Machines with More Than One Rating

7.5.1 Ratings for Multi-speed Motors

For multi-speed motors, a definite rating shall beassigned for each speed.

7.5.2 Rating for Machines with VaryingQuantities

When a rated quantity (output, voltage, speed, etc)may assume several values or vary continuouslywithin two limits, the values shall be stated at theselimits. This provision does not apply to voltagevariation of N percent or to star-delta connectionsintended for starting.

8 MACHINES FOR NON-STANDARDVOLTAGES, FREQUENCY AND NUMBER OFPHASES

Machines within the scope of this standard for use onsystems complying voltages, frequencies and phasesother thun standard shall be considered as complyingwith this standard provided they comply with thisstandard in all other respects. The voltages, frequencyand number of phases for which they are designedshall be stated on the rating-plate.

9 IRREGULARITIES OF WAVEFORM

9.1 The requirements of this clause apply only tosynchronous machines of 300 kW or (kVA) or above,intended for connection to power networks operatingat rated frequencies of 16 2/3 Hz 100 Hz inclusive,with a view to minimizing interference between power’lines and adjacent circuits.

9.1.1 Requirements

When tested on open circuit and at rated speed andvoltage, the telephone harmonic factor (THF) of theline-to-line terminal voltage as measured accordingto 9.1.2 shall not exceed the following value:

Rated Output THF,percent

300 kW (or kVA) e P S 1000 kW (or kVA) 5

1f)CtOkW(orkVA)<PS5000 kW (or kVA) 3

5000 kW (or kVA) < P 1.5

NOTES

1 Limiting values of individual harmonics are not specified asit is considered that machines which meet the aboverequirements shall be operationally satisfactory,

2 Where the synchronous machine is to be connected to thesystem in an unusual manner (for example, where the star pointof machine is connected to earth and the machine is not linkedto the system via a transformer), the waveform requirementsshould be agreed between the manufacturer and the purchaser.

..

6I

9.1.2 Tests conformity with 9.1.1, shall be verified bytype tests on ac generators. The range of frequenciesmeasured shall cover all harmonics from ratedfrequency up to 5000 Hz. Either the THF may bemeasured directly by means of a meter and associatednetwork specially designed for the purpose or eachindividual harmonic shall be measured and from themeasured values the THF shall be computed using thefollowing formula:

THF (percent)=1007{

E12klz+ Ez2~z2+Es 2ks2+ .....+E.2 kf12

where

En = rms value of nth harmonic line-to-lineterminal voltage,

U = rms value of line-to-line terminalvoltage of machine, and

An = weighting factor for frequencycorresponding to nth harmonic.

Numerical values of the weighting factor for differentfrequencies shall be obtained from Table 1. The curve

in Fig. 1 may be used as an aid to interpolation.

2.0

1.8

1.6

1.4mog 1.2

if* 1.0~+x 008g

; 1.6

0.4

0.2

0 0

FREQUENCY Iiz

FIG. 1 WEIGHING CURVE

10 CO-ORDINATION OF VOLTAGES ANDOUTPUTS

In the case of ac machines, the rated output should begreater than the limits given below in terms of the ratedvoltage:

Rated Voltage (UtJ Minimum Rated Output

kV kW or kVA

2< U. <3.3 100

3.3< u. <6.6 200

6.6<U. <11 1000

11 DUTY AND RATING

The type of duty and classelectrical machine shall beIS 12824.

IS 4722:2001

of rating of rotatingin accordance with

12 CONSTRUCTIONAL REQUIREMENTS

12.1 Earth Terminali

Machines shall be provided with means for connectinga protective conductor or an earth conductor, suchmeans being identified by the appropriate symbol orlegend. This requirement does not apply to machineswith supplementary insulation, to machines with ratedvoltages up to 42 V, or to machines for assembling insupplementary insulation.

12.1.1 In the case of machines having rated voltagesabove 42 V, but not exceeding 1000 V ac or 1500 Vdc, the terminal for the earth conductor shall besituated in the vicinity of the terminals for the lineconductors, being placed in “the terminal box ifprovided. Machines having rated outputs in excess of100 kW shall have, in addition, an earth terminal fittedon the frame.

12.1.2 Machines for rated voltages higher than 1000V ac or 1500 V dc, shall have an earth terminal on theframe, for example, an iron strap and in addition ameans inside the terminal box for connecting cablearmour, if any.

12.1.3 The earth terminal shall be designed to ensurea good connection with the earth conductor withoutany damage to the conductor or terminal. Accessibleconducting parts which are not part of the operatingcircuit shall have a good electrically conductingconnection with each other and with the earth terminal.The shaft need not be electrically connected to theearth terminal unless the bearings are insulated and theaccessible parts of the shaft and of these insulatedbearings can be subjected to dangerous contactvoltages under fault conditions.

12.1.4 When an earth terminal is provided in theterminal box, it shall be assumed that the earthconductor is made of the same metal as the liveconductors.

12.1.5 When an earth terminal is provided on theframe, the earth conductor may, by agreement, bemade of another metal (that is, steel). In this case, indesigning the terminal, proper consideration shall begiven to the conductivity of the conductor.

12.1.6 The earth terminal shall be designed toaccommodate an earth conductor of crosssectionalarea in accordance with the Table 2. If an earthconductor larger than the size given in the Table 2 isused, it is recommended that it should correspond asnearly as possible to one of the other sizes listed.

“,$,.$,

,-.

:

. .

7

IS 4722:2001

12.1.7 For other cross-sectional areas of the liveconductors, the earth protective conductor shall havecross-sectional areas at least equivalent to:

a) that of the live conductor for cross-sectional

areas less than 25 mm2,b) 25 mm2forcross-sectional areas between25

mm2 and 50 mm2,c) 50 percent of that of the live conductor for

cross-sectional areas exceeding 50 mm2, andd) the earth terminal shall be identified by

symbol_!_.=

12.2 Mounting Arrangements

The designation for types of construction andmounting arrangements shall be in accordance withIS 2253.

12.3 Shaft Extension Key

When the machine shaft extension is provided withkeyway, it should be provided with a full key of normalshape and length.

NOTE — The use of shaft extension key for the purpose ofvibration measurement is covered in IS 12075.

13 TEMPERATURE-RISE

13.1 The determination of temperature-rise ofrotating electrical machine delivering rated outputunder the rated condition of voltage, frequency andpower factor shall be in accordance with IS 12802.

13.2 The limits of temperature-rise applicable torotating electrical machines shall be in accordancewith Table 1 to Table 3 of IS 12802.

14 OCCASIONAL EXCESS CURRENT FOR

ROTATING MACHINES

The excess current capability of machines is given forthe purpose of co-ordinating these machines withcontrol and protective devices. Tests to demonstratethese capabilities are not a requirement of thisstandard.

The heating effect in the machine windings variesapproximately as the product of the time and thesquare of current. A current in excess of the ratedcurrent will result in increased temperattrte. Unlessotherwise agreed between the manufacturer and thepurchaser, it can be assumed that the machine will notbe operated at the excess currents specified for morethan a few short periods during the lifetime of themachine.

When an ac machine is to be used both as generatorand a motor, the excess current capability should bethe subject of agreement between the manufacturerand the purchaser,

14.1 Occasional Excess Current for ac Generators

ac generators having rated outputs not exceeding 1200MVA shall be capable of withstanding a current equalto 1.5 times the rated current for not less than 30s.

14.1.1 ac generators having rated outputs above 1200MVA shall be capable of withstanding a current equalto 1.5 times the rated current for a period which shallbe agreed between the manufacturer and thepurchaser, but this period shall not be less than 15s.

14.2 Occasional Excess Current for dc Machinesand ac Motors (Except Commutator Motors)

Three-phase ac motors having outputs not exceeding315 kW and rated voltage not exceeding 1 kV shall becapable of withstanding a current equal to 1.5 timesthe rated current for not less than 2 min.

NOTE — For three-phasemotors having rated outputs above315 kW and all single-phasemotors, no occasional excesscurrentis specified.

14.3 Occasional Excess Current for dc Machinesand ac Commutator Motors

dc motors and generators and ac commutator motorsshall be capable of withstanding at the highestfull-field speed (rated speed of a generator) andcorresponding armature voltage. A current equal to 1.5times the rated current for not less than 1 min.

14.3.1 For large machines, a shorter time may beagreed between the manufacturer and the purchaserbut this shall be not less than 30s.

15 MOMENTARY EXCESS TORQUE FORMOTORS

15.1 Polyphase Induction Motors and dc Motors

(Excluding Motors in 15.2)

The motors shall, whatever their duty andconstruction, be capable of withstanding for 15 s,without stalling or abrupt change in speed (undergradual increase of torque), an excess torque, of 60percent of their rated torque, the voltage and frequency(induction motors) being maintained at their ratedvalues. For dc motors, the torque maybe expressed interms of overload current.

15.1.1 Motors for duty Type S9 (see IS 12824) shallbe capable of withstanding momentarily an excesstorque determined according to the duty specified.

NOTE — For an approximate determination of the change oftemperature due to the course of the current-related losses,thermal equivalent time constant, determined according toIS 12S02 maybe used. In addition in the case of commutatormachine, attention, should be given to the limits of commutationcapability.

15.2 Induction Motors for Specific Applications

For motors intended for specific application whichrequire high torque (for example, for hoisting), excess

8

IS 4722:2001

torque shall be the subject of agreement between themanufacturer and the purchaser.

15.2.1 For cage-type induction motors speciallydesigned to ensure a starting current less than 4.5 timesthe rated current, the excess torque can be below thefigure of 60 percent given in 15.1, but not less than50 percent.

15.2.2 In the case of special types of induction motorwith special inherent starting properties, for examplemotors intended for use at variable frequency, thevalue of the excess torque shall be the subject ofagreement between the manufacturer and thepurchaser.

15.3 Polyphase Synchronous Motors

15.3.1 Unless otherwise agreed, a polyphasesynchronous motor irrespective of the duty, shall becapable of withstanding an excess torque as specifiedbelow for 15s without falling out of synchronism, theexcitation being maintained at the valuecorresponding to rated load. When brushlessexcitation is used, the limits of torque shall be the samevalue with the excitation equipment operating undernormal conditions:

Synchronous (wound rotor) 35 percent excessinduction motors torque

Synchronous (cylindrical rotor) 35 percent excessmotors torque

Synchronous (salient pole) 50 percent excessmotors torque

15.4 Other Motors

The momentary excess torque for single-phase,commutator and other motors shall be the subject ofagreement between the manufacturer and thepurchaser.

16 PULL-UP TORQUE

16.0 Unless otherwise specified, the pull-up torque ofcage induction motors under full voltage shall be atleast equal to the following values.

16.1 Sbgle Speed Three-Phase Motors

a) For output less than 100 kW:0.5 times the rated torque, and0.5 times the locked rotor torque.

17 OVERSPEED

17.1 Machines shall be designed to withstand thespeeds specified in Table 3.

17.1.1 An overspeed test is not normally considerednecessary but can be performed when this is specifiedand has been agreed to between the manufacturer andthe purchaser (For turbine-type ac generators seealso IS 5422).

17.1.2 An overspeed test shall be considered assatisfactory if no permanent abnormal deformation isapparent subsequently, and no other deficiency isdetected which would prevent the machine fromoperating normally, and provided the rotor windingsafter the test comply with the required dielectric tests.The duration of any overspeed test shall be 2 min.

17.1.3 Due to settling of laminated rotor rims,laminated poles held by wedges or by bolts, etc, aminute permanent increase in the diameter is natural,and is not to be considered as an abnormal deformationindicating that the machine is not suitable for normaloperation.

17.2 During commissioning of a hydraulic turbinedriven synchronous generator, the machine shall bedriven at the speed it can reach with the overspeedprotection operating, so as to ascertain that the balancequality is satisfactory up to that speed.

18 UNBALANCED CURRENTS OFSYNCHRONOUS MACHINES

18.1 Unless otherwise specified, three-phasesynchronous machines shall be capable of operatingcontinuously on an unbalanced system such that, withnone of the phase currents exceeding the rated current,the ratio of the negative sequence component ofcurrent (12) to the rated current(L) does not exceed thevalues in Table 4 and under fault conditions, shall be

capable of operating with the product of (12/ln)2 and

time in second (t) not exceeding the value in Table 4.

19 SHORT-CIRCUIT CURRENT

19.1 Unless otherwise specified, the peak value of theshort-circuit current for synchronous machines, andturbine-type machines not covered by IS 5422. In caseof short-circuit of all phases during operation at ratedvoltages, shall not exceed 15 times the peak value or21 times therms value of the rated current.

b) For output equal to or greater than 100 kW: 19.1.1 For three-phase turbine-type machines, see0.3 times the rated torque, and IS 5422.0.5 times the locked rotor torque.

19.1.2 The check may be carried out by calculation or16.2 Multi-Speed Three-Phase Motors by means of a test at a voltage of 50 percent of the rated

0.3 times the rated torque.voltage or above.

8

9

IS 4722:2001

Table 4 Unbalanced Operating Conditions forSynchronous Machines

(Clause 18.1)

Item Machine Type Maxtmum (12/1.)Maximum (lz/1n)2tNo. for Continuous for Oswatfon

Operation

(1) (2) (3)

1 Salient pole machinesIndirectly cooled:

motors 0.1generators 0.08synchronous condensers 0.1

2 Directly cooled (innercooled) statorand/or field

motors 0.08generators 0.05synchronous condensers 0.08cylindrical rotor synchronousmachines

3 Indirectly cooled rotocair-cooled 0.1hydrogen-cooled 0.1

4 Directly cooled (innercooled) rotor<350 MVA 0.08>350 <900 MVA see Note 1>900<1250MVA see Note 1>1250< 1600 MVA 0.05

NOTES

Und& FaultConditions

(4)

202020

151515

1510

8see Note 2

55

1 Forthesemachines,the@ue of12/1.k calculatedasfollows:

[1s“ -35012/1. = 0.08- —

3 x 1042 For these mach:nes, the ~alue of (12/1,,)is calculated asfollows:

(12/[.)2[= (84.005 45) (S. - 350)WhereS,,is the ratedapparentpowerin MVA

20 SHORT-CIRCUIT WITHSTAND AND

EXCITATION OF SYNCHRONOUS MACHINES

20.1 Short-Circuit Withstand Test forSynchronous Machines

The three-phase short-circuit test for synchronousmachines shall be carried out only at the request of thepurchaser. In this case, the test shall be carried out onthe machine running on no load with an excitationcorresponding to the rated voltage unless otherwiseagreed. The test shall not be cat-tied out with an

excitation greater than that corresponding to1.05 times the rated voltage at no load.

20.1.1 The test excitation, as determined, may bereduced by agreement between the manufacturer andthe purchaser, in order to take into account theimpedance of the transformer which may be placedbetween the machines and the system. In this lattercase, it may also be agreed that the test be made on theoperating site with the over-excitation device inoperation. The short-circuit shall be maintained for3 s.

20.1.2 The test is considered satisfactory if noharmful deformation occurs and if the requirements ofthe applied voltage dielectric test (see 30 and Table 6)are met after the short-circuit test. For three-phaseturbine-type-machines (see IS 5422).

20.2 Excitation

20.2.1 Generator Reserve Excitation

When running at the rated operating temperature andat rated speed, generators shall be capable ofdeveloping for a short time their rated voltage and acurrent eqtrat to 125 percent of the rated current

(at rated power factor for ac generators). Forseparately excited or self excited machines, the fieldwinding shall be designed accordingly. For machineswith direct coupled exciter, the exciter shall be capableof supplying the required excitation voltage.

NOTES1 The operating conditions stated above are only intended toascertain that the reserve excitation is sufficient and are notassociated with any temperature-rise condhion. However, if thetest is carried out after a temperature-rise test, it is recommendedthat its duration be limited in order to prevent windingtemperatures from exceeding the limits of temperature resultingfrom the values specified in Tables 1to 3 of IS 12802.2 The above requirement shall not apply to compoundgenerators without any voltage regulation system.3 If the operating temperatureof field winding is not known, itshatl be considered to be 75°C for windkrg of Classes A, E andB and 115°Cfor Classes F and H.

The ceiling voltage shall not be less than 1.4 times therated excitation voltage for a minimum of 10s.

20.2.2 Ceiling Voltage (Up)

The ceiling voltage of the excitation system ofnon-compounded synchronous condensers is themaximum voltage at which the excitation system iscapable of operation, with field windings of themachine at their operating temperature.

20.2.3 Initial Excitation System Response

The initial excitation system response is the initial rateof increase in the excitation voltage expressed by itsrelative value in relation to the excitation voltage forthe rated conditions of the main machine, thetemperature being the ceiling voltage to be attained inthe shortest possible time.

The conventional expression of the initial exciatiotisystem response is:

up – Ufn P–1=—Ufn x tt tt

where

Ufn = Excitation voltage for the ratedconditions of the main machine;

up = Excitation ceiling voltage;

“

10

P = Q; ~n~Uflr

tl = The time required for the excitationvoltage U. to increase fromUfn to ( Ufn + 0.632 (UP - Ufn)).

The reciprocal of the initial excitation system responseshall be less than 2s.

NOTE — If the operatingtemperatureof field windingis notknown,it shallbeconsideredtobe75°CforwindingsofClassesA, E andB and 115°Cfor ClassesF and H.

20.2.4 Excitation Response Ratio

The excitation response ratio is the initial excitationsystem response (see 20.2.3) as calculated byreplacing the actual change in voltage by a linearvariation leading to the same mean value as measuredduring the first half second unless otherwise agreed.

In the case of a measurement made during the firsthalfsecond, the excitation response ratio will beexpressed by:

41 Ufn (0.5)– Ufn 1Ufn

Where

Ufn = Excitation voltage for the ratedcondition of the main machine; and

Ufn (0.5)= Mean value of the excitation voltageduring the first half-second.

21 LIMITS OF VIBRATION SEVERITY

Unless otherwise specified, the limits of vibrationseverity for the machine shall be within the limitsspecified in IS 12075.

22 COMMUTATION

Commutation of dc machines and ac CommutatorMotor (Excluding those of the Brush ShiftingType)

The machine shall work with brush fixed setting fromno load to the momentary overload specified in 14and 15 without injurious sparking or injury to thecommutator or brushes.

Annex B gives the details of the grades of sparking thatmay be used in specifying the degree of sparking.

23 EFFICIENCY

If a statement of efficiency is required, the purchasershall specify at the time of enquiry the load and inthe case of ac generators and synchronous motors,the power factor to which the statement shall apply.The method of arriving at the efficiency shall be asset out in IS 4889. Tolerances are specified inTable 5.

IS 4722:2001

24 POWER FACTOR

If a statement of power factor is required for aninduction motor the purchaser shall specify at the timeof enquiry the loads on which the statement is to bebased. Tolerances are given in Table 5.

25 TOLERANCES

Unless otherwise specified, tolerances shall be inaccordance with Table 5. Where a tolerance is statedin only one direction the tolerance in thi otherdirection is considered unimportant.

26 TERMINAL MARKINGS

Terminal markings, when used, shall be in accordancewith IS 4728.

27 RATING PLATES

27.1 Every electrical machine shall be provided witha rating plate (or rating plates), containing thefollowing appropriate information which shall beeasily legible and durable. This complete informationneed not be on the same plate. As far as possible, therating plate(s) shall be fixed to the frame of themachine and, unless otherwise specified, located insuch a way as to be easily legible in the position of useas determined by the type of construction of themachine.

a)

b)c)

d)

e)

0

g)h)

j)k)

m)

n)

P)

q)

r)

Reference to this Indian Standard, that is,IS 4722;The manufacturer’s name;The manufacturer’s serial number ofidentification mark and year of manufacture;Frame reference in accordance with IS 1231,if applicable;Type of machine, a motor or generator, shunt,series, compound, cage, etc;The class of rating or the duty type accordingto IS 12824;The rated voltage;The rated output in kW or kVA;The rated curren~Type of current(dc or at);Rated speed or speed range in revolutions perminute;The class of insulation or the permissibletemperature-rise;For hydrogen-cooled machines, the hydrogenpressure at rated outputThe maximum ambient temperature if themachine is designed for a maximum ambienttemperature other than 40°C, or the maximumwater temperature if the machine is designedfor a maximum water temperature other than25°C;The altitude, if the machine is designed to beused at altitude exceeding 1000 m;

(“‘4...” . . .

.

11

IS 4722:2001

Table 5 Schedule of Tolerance(Clauses 23,24 and 25)

S1No. Item(1) (2)

1 Efficiencya) By summation of losses:

Machines up to 50 kWMachines above 50 kW

b) By input-output test

2 Total losses (see Note 1) applicable to machinesabove 50 kW

3 Power factor for induction machines

4 a) Speed of dc shunt and separate excitation motors (at full load andat working temperature)

b) Speedof dc seriesmotors (at full loadand at working temperature)

c) Speed of dc compound excitation motors (at full load and at workingtemperature)

5 a) Slip of induction motors (at full load and at working temperature):1) machines having output 1 kW(or kVA) or more2) machines having output less than 1 kW (or kVA)

b) Speed of ac motors with shunt characteristics (at full load and at workingtemperature)

6 inherent voltage regulation of dc generators, shut or separately excited at anypoint on the characteristic

7 Inherent voltage regulation of generatcxswithcompoundexcitation (at the ratedpowerfactor in the case of alternating current)

8 Locked rotor current of cage induction motors with short-circuited rotor andwith any specified starting apparatus

9 Peak values of short-circuit of ac generator under specified conditions

10 Steady short-circuit current of an ac generator under specified conditions

11 Variation of speed of dc shunt-wound and compound wound motors(from no-load to full load)

12 Locked rotor torque of induction motors

13 Pull-up torque of induction motors

14 Pull-out torque of induction motors

15 Moment of inertia

16 Locked rotor torque for synchronous motors

17 Pull-out torque for synchronous motors

18 Locked rotor current for synchronousmotors19 Voltage balance test at no load

Tolerance(3)

-15percentof(l -q)-lOpercentof(l -q)-15 percent of (1 - q)

+ 10percent of the total losses

-1/6 of (1 - cos $ ) :kfin 0.02:Max0.07

f 15percenL if (kW/l CN30rev/rein)< 0.67+ 10 percent, if [0.67 < (kW/l 000 rev/rein)< 2.51+ 7.5 percent, if [2.5s (kW/ 1000 rev/rein)< 10]+ 5.o pement, if (kW/100 rev/rein) ~ 10

&20 percent, if (kW/l COOrev/rein)< 0.67f 15percent, if [0.67s (kW/l 000 revlmin) <2.51+ 10percent, if [2.5 S (kW/ 1000 rev/rein)< 101f 7,5 percent, if (kW/100 rev/rein) 210Tolerances as per item 4 (b) unless otherwiseagreed between the manufacturerand the purchaser.

i 20 percent of the guaranteed slipi 30 percent of the guaranteed slipOn the highest speed:-3 percent of the synchronous speedOn the lowest speed:+ 3 percent of the synchronous speedf 20 percent of the guaranteed regulation at thatpoint

f 20 percent of the guaranteed regulation, with aminimum of +3 percent of the rated voltage(TMs tolerance appfies to the maximum deviationat any load between the observed voltage at thatload and a stmightlinedrawn between the points ofguaranteed no-load and full-load voltage)+20 percent of the guaranteed current (no lowerlimit)* 30 percent of the guaranteed value

* 15 percent of guaranteed value

.+20 percent of the guaranteed variationwith a minimum of i 2 percent of the rated speed

-15 percent +25 percent of the guaranteed torque(+25 percent may be exceeded by agreement)+15 percent of the guaranteed torque

-10 percent of the guaranteed torque except thatafter allowing for this tolerance, the torque shall benot les rJran1.6or 1.5tis therated torque (see 15)t 10percent of the guaranteed value

-15 percent +25 percent of the guaranteed value(+25 percent may beexceded by agreement)

–10 percent of the guaranteed value except that afterallowing for this tolerance, the torque shall be notless than 1.35or 1.5timesthe ratedtorque (see 14)

+20 percent of the guranteed value (no lower limit)+1%

“

12

IS 4722:2001

s)

t)

The mass of the machine shall be indicated, ifgreater than 30kg when this indication is ofinterest; andAdditional information required, if any see27.2.

NOTE —The above items are numbered for convenientreferencebut the order in wh]chtheyappearonthe ratingplateis notstandardized.

27.2 Additional Information on Rating Plate

27.2.1 dc Machines

The rating plate shall carry the following particularsin addition to &ose given in 27.2:Rated field current and voltage, if separately excited.

27.2.2 ac Generators

The rating plate shall carry the following particularsin addition to those given in 27.1:

a)

b)

c)

d)

e)

Rated frequency in Hz and number of phases;Power factor;Winding connectors designated by appropriatesymbols in accordance with IS 4728;Rated field (excitation) current and voltage atrated output; andThe permissible overspeed, if applicable (forexample, turbine-type generators andhydraulic-turbine driven generators).

27.2.3 Synchronous Motor or Synchronous InductionMotor or Condensers

The rating plate shall carry the following informationor rating plate, in addition to those given in 27.1:

a)

b)

c)

d)

e)

f)

g)

h)

j)

27.2.4

Rated frequency in Hz and number of phases;

Winding connections designated by ap-propriate symbols in accordance with IS 4728;

Rated input in kVA or MVA, in case ofsynchronous condensers;

Rated current in amperes or rated output (formotors) and input (for condensers)

Rated field (excitation) current and voltage atrated input for separately excited machines;

Power factor;

For asynchronous motor intended to be startedas an induction motor, standstill voltage be-tween the sliprings (or secondary terminals) instarting condition;

Secondary current for synchronous inductionmotOrs; and

Permissible overspeed, if applicable.

Irrduction Motor and ac Commutator Motor

The following information, in addition to 27.1, shallbe given on the rating plate:

a)

b)

Frequency in Hz;

Number of phases and winding connections

c)

designated by appropriate symbols in accord-ance with IS 4728; and

For wound-rotor (slipring) machines, opencircuit rotor voltage and full load rotor current.

28 INFORMATION TO BE GIVEN WITHENQUIRY AND ORDER

The details are given in Annex C.

29 TESTS

29.1 General

The tests specified in these clauses shall normally becarried out at manufacturer’s works.

29.2 Test Certificates

29.2.1 Unless otherwise specified when invitingtenders, the purchaser if so desired by themanufacturer, shall accept manufacturer’s certificate,as evidence of the compliance of the machine with therequirements of temperature-rise test (see IS 12802),14 and 15 on a machine identical in essential detailswith the one purchased, together with routine tests oneach individual machine. In the case when a batch of20 or more similar machines is supplied on one order,type tests, as specified, shall be made on one of these.-machines, if the purchaser so requires.

29.2.2 Certificates of routine tests shall show that themachine purchased has been run and has been foundto be electrically and mechanically sound and inworking order in all particulars.

29.2.3 If so specified, at the time of enquiry, tests shallbe carried out at the manufacturer’s works in thepresence of the purchaser or his representative toensure that the machine complies in every respect withthe requirements given in this draft standard andagreed to earlier at the time of agreement.

29.2.4 Certificates of all type tests together with arecord of any alterations, whether essential or not,which have been made to the machine since the typetests were carried out, shall be kept available by themanufacturer for inspection.

29.3 Classification of Tests

NOTE — Impulse tests on windings of rotating electricalmachines are under consideration.

29.3.1 Induction Motors and Generators

29.3.1.1 Type tests

The following shall constitute the type tests:

13

c. ,————

A

IS 4722:2001

a)

b)

c)

d)

e)

f-)

g)h)

j)

k)

Measurements of stator resistance and rotorresistance of slipring motors;No load running of motor and reading of volt-age, current, power input and speed;

Open circuit voltage ration on slipringmotors:

Reduced voltage running up test at no load (forsquirrel cage motors only)

To check the ability of the motor to run up tofull speed on no load, the value of reducedvoltage in case of motors up to 37 kW shall beI/@of the rated line voltage in each directionof rotation of motors.

For motors above 37 kW, the value of reducedvoltage shall be l/~ of rated line voltage ofless but only in the specified direction ofrotation of motov

Locked rotor readings of voltage, current,power input and torque of squirrel cagemotors;

NOTE —This test may be made at a reduced voltage.

Full load values of voltage, current, powerinput and slip;

Temperature-rise test;

Momentary excess torque;

Insulation resistance test (both before and afterthe high Dielectric tests); and

Dielectric tests.

29.3.1.2 Routine tests

The following shall constitute the routine tests:

a)

b)

c)

d)

e)

f)

Insulation resistance tests (before Dielectrictest only);

Dielectric test;

No load running of motor and reading ofcurrent in the three-phase and voltage;

Locked-rotor readings of voltage, currentpower input at a suitable reduced voltage;

Reduced voltage running up test at no load tocheck the ability of the motor to run up to fullspeed on no load in each direction of rotationwith l/fi of the rated line voltage applied tothe stator terminals (for squirrel cage motorsonly); and

Open circuit voltage ratio (for slipring motorsonly).

29.3.2 Synchronous Motors and Generators

29.3.2.1 ;ype tests

The following shall constitute the type tests:

a) Measurement of winding resistance;b) Phase sequence test;c) Regulation test (for generators only);

d)

e)

f)

g)h)

j)k)

m)

n)

P)

@

r)

s)

t)

Measurement of leakage reactance and potierreactance (for generators only);Measurement of open-circuit characteristic(for generators only);

Measurement of short-circuit characteristic(for generators only);

Efficiency test;

Temperature-rise test;

Occasional excess current test;

Overspeed test

Insulation resistance test (both before and afterDielectric test);

Dielectric tes~

Starting current and torque test (forsynchronous motors);

Determination of deviation of voltage wage-form from sinusoidal (for generators only);

Measurement of bearing current for machinesabove 1000 kW;

Short-circuit withstand test and measurementof reactance and time constants (for generatorsabove 1000 kW only); and

Pressure test on coolers for closed circuitcooling.

29.3.2.2 Routine tests

The following shall constitute the routine tests:

a)

b)

c)

d)

e)

f)

@h)

j)

Measurement of winding resistance;

Insulation resistance test;

Phase sequence test;

Regulation test (for generators only);

Measurement of open-circuit characteristic(for generators only);

Measurement of short-circuit characteristic(for generators only)(see Note 1);

Dielectric test;

Measurement of bearing currents for machinesabove 1000 kW; and

Pressure test on coolers for closed-circuitcooling.

29.3.3 de Motors and Generators

29.3.3.1 Type tests

The following shall constitute the type tests:

a)

b)

c)

d)

Measurement of winding resistance;

Measurement of insulation resistance;

Determination of open-circuit characteristics(subject to agreement between the purchaserand the supplier);

Determination of regulation characteristics(subject to agreement between the purchaserand the supplier);

-.“,.“

..

14

e)

f).9h)

j)

k)

m)

n)

Determination of external characteristics( forgenerators only) this test shall be applicable forgenerators having output ratings above150 kW and shall be subject to agreementbetween the purchaser and the supplie~

Temperature-rise test;

Commutation-rise test;

Determination of efficiency of machines;

NOTE — For sliprings alternators these tests areconducted with respect to main field current and forbrusbless these tests are carried out with respect to fieldcurrent.

Load saturation characteristics (for excitersonly);

Nominal exciter response for dc exciters(subject to agreement between the purchaserand the supplier);

Overspeed test; and

Dielectric test.

29.3.3.2 Routine tests

The following shall constitute the routine tests:

a) Measurement of winding resistance;

b) Measurement of insulation resistance, beforeand after high voltage test;

c) Commutation test; and

d) Dielectric test.

30 ELECTRIC STRENGTH

30.1 Dielectric Test

30.1.1 The high voltage shall be applied between thewindings under test and the frame of the machine withthe core and the windings not under test connected tothe frame. It shall be applied only to a new andcompleted machine with all its parts in place underconditions equivalent to normal working conditionsand shall be carried out at the manufacturer’ works.When the temperature-rise test is carried out, thedielectric test shall be carried out immediately afterthis test.

30.1.2 In the case of polyphase machines with ratedvoltage above lkV having both ends of each phaseindividually accessible, the test voltage shall beapplied between each phase and the frame, with thecore and the other phases and windings not under testconnected to the frame.

30.1.3 The test voltage shall be of power-frequency and shall be as near as possible to sine waveform.

IS 4722:2001

30.1.4 The test shall be commenced at a voltage of notmore than one half of the full test voltage. The voltageshall then be increased to the full value steadily or insteps of not more than 5 percent of the full value, thetime allowed for the increase of the voltage from halfvalue being not less than 10 s. The full test voltageshall then be maintained for 1 minute in accordancewith the value as specified in Table 6.

30.1.5 During the routine testing of quantity producedmachines, the one-minute test may be replaced:

a) for machines up to 200 kW (or kVA) and withrated voltages up to 660 V, by a test ofapproximately 5 s at the normal test voltagespecified in Table 6; and

b) for machines up to 5 kW (or kVA) by a test ofapproximately 120 percent of the normal testvoltage in Table 6.

The test voltage being applied by means of probe.

30.1.6 The high voltage test at full voltage made onthe windings on acceptance shall not be repeated. If,however, a second test is made at the request of thepurchaser after further drying if considered necessary,the voltage shall be 80 percent of the voltage specifiedin Table 6.

30.1.7 Completely rewound windings shall be testedat the full test voltage for new machines.

30.1.8 When a user and a repair contractor haveagreed to carry out dielectric tests in cases wherewindings have been partially rewound or in the caseof an overhauled machine, the following provisionsare recommended:

a) Partially rewound windings are tested at75 percent of the test voltage for a newmachine. Before the test, the old part of thewinding shall be carefully cleaned and dried;and

b) Overhauled machines after cleaning anddrying are subjected to a test at a voltage equalto 1.5 times the rated voltage with a minimumof 1 000 V if the rated voltage is equal to orgreater than 100 V and a minimum of 500 voltif the rated voltage is less than 100 V.

30.2 Insulation Resistance Test

30.2.1 The procedure for determination of insulationresistance of insulated parts of the machines given inIS 7816 shall be followed. The value of recommendeddc voltage at which the test may be carried out aregiven in Table 7.

15

IS 4722:2001

Table 6 Dielectric Tests(Clauses 30.1.4,30.1.5 and 30. 1.6)

A

sl Machine or PartNo.

(1) (2)

1)Insulated windings of size less than 1kW (or kVA)and of ratedvoltage less than 100V with the exception of those S1No. (d)to (h)

2) Insulated windings of rotating machinesof size less than 10000kW (or kVA) with the exception of those in item (a) and S1No.(d) to (h) (see Note 2)

3) Insulated windings of rotating machines of size 10000 kW(or kVA) or more with the exceptionof drme in S1No. (d) to (h)(seeNote2)Rated voltage (see Note 1):

Upto24W30Vabove24CMlV

4) Separately excited field windings of dc machines

5) Field windings of synchronous generators, synchronousmotorsand synchronous condensers:a) Rated field voltage Up to 500 V

Above 500 Vb) When a machine is intended to be started with field winding

short-circuited or connected across a resistance of the valueless than ten times the resistance of the winding

c) When the machine is intended to be started either with thefield winding connected across a resistance of value equalto or more than ten times the resistance of the winding orwith the field windings on open circuit with or without afield dividing switch

6) Secondary (usually rotor) windings of induction motors orsynchronousinductionmotorsis not permanentlyshort-circuited(for example, if intendedfor rheostaticstarting):a) For non-reversing motor or motor reversible from standstill

only; and

b) For motors to be reversed or braked by reversing theprimary sLIpplywhile the motor is running

7) Exciters (except as below)

Exception 1 — Exciters of synchronous motors (Includingsynchronous induction motors) if connected to earth ordisconnected from the field windings during starting.

Exception 2 — Separately excited field windings of excitersIsee S1No. (4)]

8) Assembled group machines and apparatus

NOTES

Test Voltage (rms)

(3)

500 V + twice the rated voltage

1000 V+ twice the rated voltage with a minimum of 1500 V (seeNote 1)

1000 V+2U,where U is the rated voltageSubject to agreement between the manufacturer and the purchaser

1000 V+ twice the maximumrated circuit voltage with a minimumof1500v

Ten times the rated field voltage with a minimum of4000 V+ twice the rated field voltageTen times the rated field voltage with a minimum ofmaximum of 3500 V

500 v

500 V and

1 000V + twice the maximum value of the rms voltage which canoccur under the specified starting conditions between the terminalsof the field winding or in the case of a sectional field windingbetween the terminals of any section with a minimum of 1500 V(see Note 3)

.’

1 000V+ twice the open-circuit standstill voltage as measurebetweensiiprings of secondary terminals with rated voltageappliedto the primary windings1000V+four times the open-circuit standstill secondary voltage asdefined in S1No. 6(a)

As per the windhrgs to which they are connected

1000 V + twice the rated exciter voltage with at minimum of1500V

A repetition of the test in S1No. 1to 6 above should be avoided, ifpossible, but if a test on an assembled group of several pieces ofnew apparatus each one of which has previously passed its highvoltagetest, is made the test voltage to be applied to such assembledgroup shall be 80 percent of the lowest test voltage appropriate forany part of the group (see Note 4)

1 For two-phase windings having one terminal in common, the voltage in the formula shafl be the highest rms voltage arising betweenany two terminals during operations.2 High-voltage tests on machines having graded insulation should be the subject of an agreement between the manufacturer and thepurchaser.3 The voltage occuring between the terminals of the field windings, or sections thereof under the specified starting conditions maybemeasured at any convenient reduced supply voltage and the voltage so measured shall be increased in the ratio of specified startingvoltage to the test supply voltage.4 For windings of one or more machines connected together elcctnca\Iy the voltage to be considered is the maximum vohage thatoccurs in relation to earth.

16

------ -.. .

.‘..-.! L

..

Table 7 Test Voltages for Insulation Resistance(Clause 30.2.1)

Rated Voltage Test Voltagefor Insulationac Resistance, dc(1) (2)

Up to 660 5MIvAbove 660 up to and 1000 V or higher value as agreedincludhrg I 100 between the manufacturer and the

mer

30.2.2 The minimum values of insulation resistanceshall be determined by the following empiricalrelationship:

Where

R. =

kv =

Rm=kV+l

Minimum insulation resistance inmegaohms at 40°C of entire machinewindings; and

Rated voltage of the motor, in kilovolts.

NOTE — Rm at 40° C is in effectonemegaohmper 1000 voltsplusonemegaohm.

30.2.3 ac machines rated above 3.3 kV and havingoutput more than 1 000 kW may also be tested forpolarization index (PI) of insulated windings. Themethod for measurement of polarization index shall bein accordance with IS 7816. The minimum values ofPI (lRlornin/lRl rein) shall be 1.5 for Class A, 2.0 for

Class B and 1.75 for Class E insulation systems.

NOTE — The recommended minimum value of PI(!~=vhq~~)shall be 1.3 for all classes of insulations of thewindings.

31 COMMUTATION TEST

31.1 The commutation test shall be made to verify themachine meets the requirements specified in 22 of this

IS No.

1076:1985

1231:1974

1885(Part 35) :1993

2253:1974

1s 47LL : Z(JU1

standard. In case of type test, this is to be carried outat the conclusion of the temperature-rise test of themachine.

32 OVERSPEED TEST

The test, if agreed, shall be made, to verify therequirements of 17 of this standard.

33 UNBALANCED CURRENTS OFSYNCHRONOUS MACHINES

The test, if agreed, shall be carried out to verify theprovisions of 18 of this standard.

34 SHORT-CIRCUIT CURRENT TEST

The test, if agreed, shall be carried out to verify theprovisions of 19 and 20 of this standard.

35 OCCASIONAL EXCESS CURRENT

This test shall be carried out to verify the provisionsof 14 of this standard.

36 MOMENTARY EXCESS TORQUE

This test shall be earned out to verify the provisionsof 15 of this standard.

37 PULL UP TORQUE FOR MOTORS

This test shall be carried out to verify the provisionsof 16 of this standard.

38 LIMITS OF VIBRATION

If agreed between the user and the manufacturer, thistest may be arranged to verify the specified limits ofvibration according to IS 12075.

ANNEX A

(Clause 2)

LIST OF REFERRED INDIAN STANDARDS

Title IS No.

Preferred number (second revision) 4691:1985

Dimensions of three-phase foot-mounted induction motors (thirdrevision) 4728:1975

Electrotechnical vacabulaty: Part 35Rotating machinery (first revision)

4889:1968

Designation for types of constructionand mounting arrangement of rotat-ing electrical machines (tirst 5422:1996revision)

17

Title

Degrees of protection provided byenclosures for rotating electricalmachines (tlrst revision)

Terminal marking and direction ofrotation for rotating electricalmachinery (first revision)

Method of determination of ef-ficiency of rotating electricalmachines

Turbine type generators

IS 4722:2001

IS No.

6362:1995

7816:1975

12075:1987

Title IS No. TitleDesignation of methods of cooling 12360:1988 Voltage bands forelectrical installa-for rotating electrical machines tion, including preferred voltages andGuide for testing insulation resis- frequencytance of rotating machines 12802:1989 Temperature-rise measurement ofMechanical vibration of rotating rotating electrical machineselectrical machines with shaft 12824: 1989 Types-of duty classes of ratingheights 56 mm and higher-measure- assigned to rotating electricalment, evaluation and limits of vibra- machinestion severity

ANNEX B

(Clause 22.1)

GRADES OF SPARKING

B-1 GRADES B-1,1 No. 1 and No. 2

B-1.O The following grades of sparking maybe used No blackening of commutator and burning of brushes.to specify the degree of sparking.

No.1

E!lnABSENCE OF SPARKING(BLOCK COMMUTATION)

No. 1+

SLIGHT PIN POINT SPARKINGUNDER SOME OF THE BRUSHES

No.1+

B

SLIGHT SPARKING UNDEROF THE BRUSHES

MOST

No.2

MODERATE SPARKING ON ALLTHE BRUSHES

No.3

No.4

HEAVY SPARKING ON ALLTHE BRUSHES

VICIOUS SPARKING ON ALLBRUSHES WITH STREAMERSOR GLOWING

THE

f ,.— -

4

-,

.,,. . ..*

,.

18

IS 4722:2001

B-1.2 No.1 B-1.4 No.3

Traces of black spots on commutator which can be Permitted only for direct on load starting and for theremoved by petrol. Traces of burning on brushes. starting period. Easily spottable blackening of

B-1.3 No. 2commutator which cannot be removed by petrol.Burning and slight damaging of brushes.

Permitted only for short time overloads. Trace of B ~ ~ No dblack spots on commutator which cannot be removed - “ “by petrol. Traces of bums on brushes. To much blackening of commutator which cannot be

removed by petrol. Damaging of brushes.

ANNEX C

(Clauses 28 and 31.3)

INFORMATION TO BE GIVEN WITH ENQUIRY AND ORDER

C-1 GENERAL

When enquiring for an ordering an electrical machineto comply with this standard, the following particularsshould be supplied:

a)b)c)d)e)

f)

@

h)

j)

k)

m)

n)

c-2

Site operating conditions;The number of Indian Standard;The type of enclosure;The type of duty;The maximum temperature of the cooling air,if it exceeds 40°C or of the cooling water, if itexceeds 25°C at the place where the machineis intended to work under ordinary service;The altitude of the place at which the machineis intended to work in ordinary service, if itexceeds 1000 m;If the machine is required to operate betweenvarious limits of voltage, current, frequency orspeed, the corresponding values of the voltage,current, frequency and speed respectively;System of earthing, if any, to be adopted;Particulars of tests required and where they areto be carried out;Particulars as to whether voltage-limitingdevices will be employed;Whenever a motor or generator is associatedwith a reciprocating machine, any informationregarding the associated machine which willenable the natural frequency of torsionalresonance of the combined unit to be deter-mined; andThe additional information required by thefollowing clauses of this Annex where ap-plicable.

ADDITIONAL INFORMATION FORDIRECT CURRENT GENERATOR

When enquiring for and ordering a direct currentgenerator, the following particulars should be suppliedin addition to the requirements of C-1.

a) Electrical output at the terminals, in kilowatts;

b)

c)d)

e)

f-)

!3)

h)

Rated voltages. If the voltage at rated load isrequired to be different from no-load voltage,full particulars should be given;Current, in amperes;If required for 3-wire operation, full details ofrequirements;Speed, in revolutions per minute at no-load andat rated load;Direction of rotation;Method of excitation, whether shunt, series,compound or separately excited. If separatelyexcited, indicate excitation voltage.

NOTE — Unless otherwise specitied, the series windingof a compound generator will be connected on thenegativeside of the armature.

When a dc generator is required to operate inparallel with others, the following details ofexisting machines should be given:

1)2)3)

4)5)

6)

Voltage at no-load and-at rated load;kW or current at rated load;Resistance of series winding includingdiverter, if any;Diagram of connections;Nominal response ratio of the excitecandWhether the exciter is required tooperate as a shunt machine on handcontrol.

C-3 ADDITIONAL INFORMATION FORDIRECT CURRENT MOTOR

When enquiring for and ordering a direct currentmotor, the following particulars shall be supplied inaddition to the requirements of C-1:

a)b)c)d)e)

Mechanical output, in kilowatts;Rated voltage;Speed, in revolutions per minute, at rated output;Direction of rotation;Method of excitation, whether shunt, series,compound or separately excited. If separatelyexcited, indicate excitation voltage;

,----

.

19

IS 4722:2001

0 Breakaway torque required; andg) Any information regarding the driven machine

which has a bearing upon the torque requiredduring the accelerating period, the kineticenergy of the moving parts to be accelerated,and the number of starts during a specificperiod.

C-4 ADDITIONAL INFORMATION FOR acGENERATOR

When enquiring for and ordering an ac generator, thefollowing particulars should be supplied in addition tothe requirements of C-1:

a)b)

c)d)e)

f)

g)

h)

j)

k)

m)

n)

P)q)

Frequency, in Hz;Number of phases and in the case polyphasemachines, the interconnection between thephases, if any;Electrical output, in kVA or MVA;Rated voltage;Power-factor, if other than 0.8;Current, in amperes;Speed, in revolutions per minute, at no-loadand at rated load;Direction of rotation;Whether the machine is to have its own exciter,and if so, the methods of drive or whether theexcitation is to be obtained from a separatesource;Excitation voltage, if the generator is not to beprovided with its own exciteqConditions to be met in cases of paralleloperation;Whether the neutral point is to be brought outto a terminal to deal with current in the neutralline in normal service, and, if so, the magnitudeof current in amperes to be carried;Short-circuit ratio; andUnder excited MVAR.

NOTE — Similar information should be furnished forsynchronouscondensers.

C-5 ADDITIONAL INFORMATION FORSYNCHRONOUS MOTOR ORSYNCHRONOUS INDUCTION MOTOR

When enquiring for and ordering a synchronousmotor, the following particulars should be supplied inaddition to the requirements of C-1:

a)b)

c)d)e)

Frequency, in Hz;Number of phases and, in the case of polyphasemachine, the interconnection between thephases, if any;Mechanical output, in kilowatt;Rated voltage;Speed, in revolutions per minute;

f)

/3)h)

j)

k)

m)

n)

Direction of rotation of machine and phasesequence of supply;Method of starting to be employed;Breakaway torque required;Nature of the load and any information regard-ing the driven machine which has a bearingupon the torque required during the accelerat-ing period, the kinetic energy of the movingparts to be accelerated, and the number ofstarts during a specified period;Any information having bearing on the use ofthe motor for supplying wattless current.Unless otherwise specified, the machine willbe designed for unity power factor at its ratedmechanical output;Whether the machine is to have its own exciterdriven through the motor shaft, or whether theexcitation is to be obtained from a separatesource; andExcitation voltage, if the motor is not to beprovided with its own exciter.

C-6 ADDITIONAL INFORMATION FORINDUCTION MOTOR OR ac COMMUTATORMOTOR

When enquiring for and ordering an induction motor,the following particulars should be supplied inaddition to the requirements of C-1:

a)b)c)d)e)

f)

g)h)

j)k)

m)

n)

Frequency, in Hz;Number of phases;Mechanical output, in kilowatt;Rated voltage;Speed in revolutions per minute, at the ratedoutput;Direction of rotation;Rotor, whether squirrel cage or slipring;Type of slipring gear, whether continuouslyrated or for starting purposes only and whetherto be fitted with brush lifting and/ or short-circuiting arrangements and if inler-iocks arerequired;Method of starting to be employed;Breakaway torque in terms of the rated loadtorque and the corresponding breakaway start-ing current which may be taken from thesupply with the starting apparatus in circuit;Nature of load and any information regardingthe driven machine which has a bearing uponthe torque required during the accelerationperiod, the kinetic energy of the moving partsto be accelerated, and the number of startsduring a specified period; andWhere possible, fault capacity of the system towhich the motor is connected.

$,

d

“.-..,’

.

20

I/

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in “writing of BIS. This does not preclude the free use, in the cotrrse ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed

periodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of‘BIS Catalogue’ and ‘Standards: Monthly Additions’.

This Indian Standard has been developed from Doc : No. ET 15 ( 3059 ).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

BUREAU OF INDIAN STANDARDS

Headquarters :

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telegrams : ManaksansthaTelephones :323 Of 31, 3233375,3239402 (Common to all offices)

Regional Offices : Telephone

Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg

{

3237617NEW DELHI 110002 3233841

Eastern : 1/14 C.I.T. Scheme VII M, V. I. P. Road, Kankurgachi

{

3378499,3378561CALCUTTA 700054 3378626,3379120

Northern : SCO 335-336, Sector 34-A, CHANDIGARH 160022

{

603843602025

Southern : C. I. T. Campus, IV Cross Road, CHENNAI 600113

{

2541216,25414422542519,2541315

Western : Manakalaya, E9 MIDC, Marol, Andheri (East)

{

8329295,8327858MUMBAI 400093 8327891, 8327892

‘.

.

;

Branches : AHMEDABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE.

FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR.LUCKNOW. NAGPUR. NALAGARH. PATNA. PUNE. RAJKOT. THIRWANANTHAPURAM.

Printed at Prabhat Offset Press , Daryfi Ganj, New Delhi-2