Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 13555 (1993): Guide for Selection and Application of3-Phase A. C. Induction Motors for Different Types ofDriven Equipment [ETD 15: Rotating Machinery]

r

Indian Standard

GUIDEFOR SELECTlONANDAPPLTCATIONOF 3-PHASEA.C.INDUCTrON MOTORSFOR

DIFFERENTTYPESOFDRIVENEQUIPMENT

UDC 621*313*333*025*3

0 BIS 1993

BUREAU OF INDIAN STANDARDS MANAK HHAVAN, Y BAHADUR SHAH ZAFAR MARG

NEW DELHl 110002

Muy 1993 Price Group 6

Rotating Machinery Sectional Committee, ET 15

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards after the draft finalized by Rotating Machinery Sectional Committee had been approved by the Electrotechnical Division Council.

An electric motor is meant for conversion of electrical energy into mechanical energy, Mechanical energy is required in industries to drive machines such as compressors, cranes, crushers and locomotives and in agriculture to drive irrigation pumps and other farm equipment. The installation sites of machines in industries differ in nature from industry to industry. Installations may be both outdoor or indoor, in humid or in dry weather. Requirements too, differ from industry to industry depending upon a variety of ultimate applications.

In addition to above, there are other important factors such as, and the equipment to be driven,

characteristics of driving equipment characteristics of supply system, environmental conditions and the

economic considerations for a particular application. Attempt is made in this Guide to enable the user of an electric motor to appreciate the overall situation and thereby make the right selection of the electric motor for a particular application.

This Guide does not include requirements for motors to be used in hazardous area.

Selection of electric motors for different driven equipment requires careful consideration of the various features and characteristics of the motor. Table 1.

General factors involved in motor selection arc given in Table 2 provides guidance for selection of requirements of a motor. Basic steps to select the

motor are listed in Table 3 and guide for selection of induction motors for different applications is provided in Tables 4, 5 and 6.

These tables may prove useful as a check-list in determining the requirements in motor specifications or in considering the motor features required for a new application.

The size chosen shall satisfy the customers on all performance parameters including power factor and efficiency. Optimizing the system efficiency would be the responsibility of the system designer. From the point of view of energy conservation, be necessary.

information on power factor and efficiency would, therefore,

Indian Standard

IS 13555: 1993

GUIDE FOR SELECTION AND APPLICATION OF THREE-PHASE A.C. INDUCTION MOTORS FOR

DIFFERENT TYPES OF DRIVEN EQUIPMENT 1 SCOPE

1.1 This Guide covers selection and application of three-phase induction motors for driving different equipments for industrial and agricultural use.

1.2 The guidance for installation and maintenance of 3-phase induction motors is covered in IS 900 : 1965 ‘Code of practice for installation and maintenance of induction motors (revised)‘.

2 RH~ERENClS STANDARDS

The list of Indian Standards given in Annex A arc necessary adjuncls to this Guidr.

3 TERMIN0I,<KY

For the purpose of this Guide, the definitions given in IS 1885 (Part 35) : 1973 and IS 325 : 1978 shall apply.

4 EXCHANGE OF INFORMATION

The engineers responsible for the selection of electric motor for the given application (driven equipment) should be aware of the exact duties, locations and condi- tions under which it is expected to operate. This informa- tion should be exchanged with the motor manufacturer for proper matching between the load and the prime mover for attaining maximum elliciency and safety ofthe installed equipment and the installation as well.

5 CHARACTERISTXCS OF DRIVEN EQUIPMENT

5.1 The following particulars of the driven machine must be known exactly for selecting the motor suitable for the specific application :

Name;

Brief description of the equipment;

Power required in kW;

Rated speed of operation;

Torque speed characteristics of the load;

Type of duty;

Moment of inertia of the rotating parts; and

Method of drive, whether directly coup!ed, belt, gear or chain driven which contribute to the mechanical efficiency of the drive.

5.2 Determination of Full had Output of Driven Machine

Mechanical input required by the driven machine should be calculated accurately taking into account cfficicncy of the driven machine itsclfend the cfficicn- c’y of the system (including that of the coupling used). Tllc formulae ofcalculaling uwtur oulpul ‘,P’ arc given in Annex 8.

5.3 I,o;~rl-‘limpe (hracteristics

5.3.1 Torque-Speed Chracteristics

The curve giving the relationship between torque and speed of the driven machine plotted as a function of the speed within the particular range is required for deter- mining the starting and braking conditions. The various types of loads occurring in practice are broadly clas- sified into four groups shown in Fig. 1. These are :

a)

b)

C)

4

The torque remaining practically constant throughout the speed; the power varies in proportion to the speed. These chardcteristics arc typical for hoisting equipment, reciprocat- ing pumps and compressors operating against a constant pressure; soot blowers, rolling mills, belt conveyors, mills without fan action, and machine tools with a constant cutting force. These characteristics are also typical for machines which should overcome the gravity, sometimes also for shears, punching machines and wood grinders.

The torque increasing in proportion to the speed; the power in proportion to the square ofthe speed.

These characteristics are typical for machmes smoothening cloth and paper, calendering machines, etc.

The torque increasing in proportion to the square of the speed; the power in proportion to the third power of the speed. These characteristics are typical for centrifugal pumps, fans and reciprocating machines feed- ing into an open pipe system.

The torque decreasing inversely proportional to the speed; the power remaining constant. These characteristics are important for automat- ic control process only, for example, for lathes and similar machine tools, winders and wood peeling machines.

5.4 Moment of Inertia

5.4.1 The moment of inertia of the driven machines (GD2) is determined in case of homogcnous bodies, by knowing the weight (of rotating parts) G in kg and diameter of gyration D.

The moment of iqertia of the rotating parts of the driven machine in kgfm” referred for the motor speed must be known for evaluating the starting and braking conditions:

GD’ (ol’the driven machine) rcfcrrcd to Motor Speed n

((;I)’ (of the dtivcn machine) x (Speed of driven machine)’

Tolal G’D’, referred to mo;‘,r shaft is then,

SPEED

Variation of torque in relation to speed : a) constanl torque ( h) lncrcasing torque in linear relation,

c) Iucrcasinp torque in square relation, and

d) Decreasing torque.

Gd (total) = CD’ (Motor) + GD2 (Driven machine); referred to motor speed n.

7 NOTE-It is a common practice to use./ = y as the

term tix moment of inertia. While specifying the diitil lilr

the mechanism, it shall Ix clarified which information is

being given.

6 SELECTION OF ELECTRIC MOTORS

6.1 Type of Motor

6.1.1 Whcrc Ihe primary requiremcnl is fur a cvtistant speed drive, the first choice is almost always the cage- type induction motor, mainly on accounl of its simplicity, robust construction and low initial cost.

Although much has been said in the pas1 about startittg of motors through voltage or winding c.onncction con- trol (resistance, star/delta and entn-transfnrrner

starters), much larger and gcncrally stiffer supply sys- tems are now available, which pcrntil [he USC uf 'direct on-line start’ of tttoturs. This hab tttadc thr dcsigtts simpler and cfficicnl. Therefore, uttlcss ilbS~~lUlely necessary, it direct on-littc start is 10 bc prcfcrred and as slated in 4, the inforniatiun un duties and pcrli9rmattce dcsircd WI of’ thr mechanism, shard freely wilb [he 11m1or mattufaclurcr, so th;tt an ~l’licicn~ tttotur ct~uld bc scl~~ted out of !lic larger variety of dcsigtts tt(.~w pos- sible. A mo1or with ;I higher villuc 01 stilrtittg c’urrrttl

may be more efficient.

Relatively ntinor modifirations to the rotor windittgs (using deep bars, or double-cage designs) enahlc machines to have significantly better starting perfor- ntancc than the simple cage tttachine. For indanrc, low starting current designs are readily available as ;tre high torque designs in which the breakaway torque of Ihe machine exceeds iwicc the full-load torque. Special tlcsigta, ptirdcularly lhosc based on the double cage cundruction, enable other combinations of torque and current IO I9c achieved lo match 11tc particular require- IIKIILS trl’the drive and supply system.

Although primarily a f’ixcd sped machine, the c;Igt! type inductim motor can easily bc wound to give IWO distinct synchronous speeds by adopting tither of the followitt~ methods :

a ) bj

(‘1

Appropriately connecting the slator winding;

Accntttmod;tlittg Iwo scparatc windings in lhc slator, wound li9r dil’krittg ttuttthcr ol’poles it ntl

ctiergizcd iIS required; and

IJlilizing pnle-;lll~plitutIr-lllotlul;ltitrl~ (PAM) techniques.

6.1.2 Where lh(& drive rcquircs ;III ;xljubt;tb!c hpccd

v;iluc of one or ntorc fixed ~~cYxI~, lhc chclicr 01‘ tt901or ryl9r widens cY~nsideritbly. Slip-ring: ittdudion ntljlor5 willt rolor K3iSliiIlCC c‘ottlrctl ilIT oflclt ;Idoplcd lor

IS 13555 : 1993

6.3 Enclosures of Motors

6.3.1 The primary function of the motor enclosure is to provide the required degree of protection to the vital part of motor as well as to the working personnel. The detailed information on degrees of protection provided by enclosures is given in IS 4691 : 1985. The two basic types of frame constructions are totally enclosed type and open type, with additional protection against dripping and splashing of liquids, dusts, etc. Depending upon the location of the machine a suitable enclosure has to be chosen. In practice, it is usually found that, where normal condition5 exist in a factory, simple drip-proof (IP 22) enclosures are by far the most suitable and if positioned sensibly, will give all the protection required with the minimum of interference to ventilation of machine. In fertiIizer and chemical plants, the enclosures should provide mechanical as well as chemical protection to the motors with the minimum of iuterference to ventilation of machine.

The totaly enclosed motor (protection IP 54), whilst of course giving perfect mechanical protection, is larger in size and costs considerably more than its standard screen-protected counterpart, and it is very much open to question whether its installation is justified in a factdry where the atmosphere and general humidity are nqmal.

6.3.2 It is appreciated that there are many situations _Z in’factories, where the working conditions are between

the two extremes, one definitely necessitating totally enclosed motors and second those approaching clean laboratory conditions, where ordinary screen protected versions will operate successfully. In such situation, there are many other types of motor enclosures which will operate very efficiently. For example, piped venti- lated motors method of cooling IC 37 of IS 6362 : 1971 are,very suitable for conditions encountered in saw mills, though in extreme cases these usually have to be located near the outside walls of a building to facilitate the installation of the intake and outlet ventilation pipes.

6.3.3 Table 1 gives the recommendation5 for selection of motors for different application. Table 2 gives the steps for selection of requirements of a motor.

6.4 Supply System and Ambient

6.4.1 In general, a.c. and d.c. arc two supply systems. The d.c. system is used for specific requirements such as traction, steel mill drives, textiles drives etc. In the a.c. system frequencies generally standardized are 50 Hz and 60 Hz. In India 50 Hz frequency is prevalent. Furthermore, there are two types of available a.c. volt- age supplies, single phase and three phase. The single phase voltage is 240 volts and the three phase line to line voltages are standardized as preferred values 415 volts, 3.3 kV, 6.6 kV and 11 kV.

6.4.2 It is not possible to maintain voltages and fre- quencies at their rated values. Therefore, the Indian Electricity Rules 1956, permits certain variations. The parameters such as speed-torque characteristics, efficiency, power factor, slip, etc, depend upon voltage and frequency.

intern&&t duties (for instance, crane or hoist drives) where the inherently high losses of the equipment at low speed are acceptable, whereas on drives where the efficiency is important, the commutator motor is the more usual solution.

NOTE-The availability of thyristors has made it pos- sible the USC of d.c. machines on a wider variety of industrial drives. Ktherto, these had been very largely confined for certain specialist areas such as steel works, where thelargerollingmill drivewasa typical application for Ward-Leonard ser. The ease with which a normal a.~. supply can now he converted by static rectifier system to an adjustable volatge d.c. supply has led to the increasing use of thyristor-fed d.c. motors for drives requiring a wide speed range. Thyristors are also used in the various types of static frequency converter sets, the variahle frequency output being fed to induction motors, the speeds of which are then controlled in accordance with the converter output frequency.

6.2 Mountiug and Frume Number (Mounting Dimensions)

6.2.1 The simplest and the least expensive method of mounting an electric motor is the foot mounting. There are other types of mounting, such as flange mounting, (face mounting bolted directly to the machine) which are also quite commonly used. The position of the base

. mounting hdles (see IS l23 1 : 1974) with reference to each other and to the location of the shaft arc quite important in case of foot mounted motors. Similarly, it is the pitch circle diameter of mounting holes, the spigot diameter and location of the shaft from the face of the tlange, which are important in flange or face mounted motors (SW IS 2223 : 1983).

6.2.2 The fixing dimensions and the shaft extension details have been standardized in IS 2223 : 1983 and outputs are also assigned to the frames. However, the overall dintensions arc not standardized, therefore complete interchangeability is not guaranteed. Though the main fixing dimensions are usually sufficient to allow replacement by motors of different manufacture, it is recommended that user may specify the maximum permissible overall dimensions of the motors for ap- plications where the motors are required to be mounted in restricted space.

Apart from the fixing dimensions (see IS 2223 : 1983), the standard specifies the accuracies of mounting flan- ges such as concentricity and perpendicularity and accuracies of shaft runouts, as these are quite important in the case of flange mounted motors. There are two classes of accuracies, normal and precision; of which the precision class is generally on demand for special purposes:

NOTE - (Zertain mounting arrangements are possible only up to certain Crame sizes. It is, however, hoped that some day various manufacturers of motors would join together and evolve CI common standard of mounting dimensions linked with rating as in IS 123t, so that the users of large rating motors can interchange motors of one make with other.

3

IS 13555 : 1993

6.4.3 Often the USCI has a choice of supply to which a motor can be connected. In principle, motors can be satisfactorily manufactured for a wide range of voltage levels. Although the higher the voltage the larger and more expensive the motor. These differcnccs are generally small in coniparison with the levels, so that the motor supply voltage is generally settled by con- siderations other than the motor cost alone. In such circumstances, it is important to bear in mind that it is difficult to manufacture small motors for high voltages. Outputs below 100 kW at 3.3 kV, below 200 kW at 6.6 kV and below 1 000 kW at 11 kV pose difficulties in the manufacture of quality motors.

6.4.4 The standard motors (SCE IS 325 : 1978) are designed to operate under voltage fluctuatiotls up to & 6% and ambient temperature up lo 40°C in conditions ofwidervoltage fluctuatiom and alnhientsabovc40UC, these motets arc required to be deratcd. The derating factors may be obtained from motor manufacturers. However, it is necessary to give the actual voltage and ambient condition to the motor manufacturer, so that motor can be designed/sclectcd suitably.

6.5 Speed

6.5.1 Induction mtitorsare limited in theirspeeds avail- able as these are determined by the number of ‘poles’. A two-pole motor has a synchronous speed of 3 000 rpm, 4-pole has 1 500 rpm, &pole has 1 000 rpm and so on, the formula being :

Speed = 6 OOO/No. of poles (rev/minute) (for 50 Hz supply)

The most common are 4-pole and 6-pole motnrs for industrial application having the best all round charac-

teristics. The practical limit of low speed is 500 rpm

(synchronous) and when lower speeds are needed, it IS economical to consider the USC of an integral gear box and motor unit.

NOTI:-‘Synchronous’speed is never altained in prx- lice, the motor ;dways runs slower by an amount known ;Isthe’slip’.Theslipatfullloadvariesiyith the kwrating, type of motor and number of poles. II nr,rmillly VilriCh

between 0.5 percent to 10 percent.

The slip can be determined by using the following formula :

Slip = Synchronous speed - Actual

Synchronous speed

6.5.2 It is ;iot necessary to emphasize that, if ;; choice of speed is possible, it is preferable to use 4-pole motor, next a h-pole and so on. The motors haviug larger uumbcr of poles take up more space, arc more cxpcn- sivc and arc deficient in efficiency and power I’;lc,i;)r compared with the lower polarities.

2-1~01~: motors arc not recommended where the high speed is not essential as they tend to be noisy and take morr current while starting.

6.6 Output, Torques and Type of Duty

6.6.1 Starting torque required may vary between 10 percent to 250 percent of full load torque depending upon the type of machine being driven. Starting torque may vary for a given motor because of frequency of star&, temperature-rise, terminal voltage, series con- nected inductive loads, ctc and such variables should be jakcn into accourii. The mntor torque must be well above that rcquircd by the driven machine at all points up to full speed. The greater the excess torque thr more rapid the acceleration (.FPC Fig. 2).

IS 13555: 1993

(lpcn NI’/NI’

Il’44~1154

II’ Wll’ 5-l

i

Table 2 hlotor Selection Guide and Check List for Specification z

( Clnlrsc 63.3 > El E VI . .

StaIldXd 1

I I I I I I I PerCormance Dimensions Construction Enclosure Method Vibration Noise Level e

and Mounting and Degree of of Cooling Level \5 w

I 1 Protection

ctrical Features 1 Mechanical Features I

Charac:cribtlcs I I I I I I Snccd kW Toruue (‘urrent Efficxncs Overload

Slip Power Factor

I I I I I I Speed Method Method Method I;(/ kdtage

of of of ,I i Of

Starting and Eraking Reversal Load Frequent) Acceleration Time Durmg

Start

i -1empcrahxe Loca ion of Altitude

Motor on ,Mach!nc Tool, 1

Area of OpeTation

, ; ,

qwl Enclosed Corrosixr Iiatardous Non- Hazardous

L

I 1 Ty Load

I I 1 Ball Roller Sleeve Radial Axial Thrust

I I Axial PIa! Type of

Drive

Length-t Stand.trd or Special

Compression Lead Connection __ Pluccing Switch

- Miscellaneous I I I \ihralion Level Nuvse Ix\ PI SpelCk3!

Normal Finich Painl

PreciGnn A. BorC

Special

6.6.2 Whcrc I& load 10 IX carried by the tuotor is uat

constant but follaws a dcfinitc ~yclc, a graph showiug load itt kW Vs I~IIIC cmblcs dctcrtnina~ion of peak output as well as the root-uleatt square kW, which indicates the proper ttiotor rating front poitil ol

Iciitpcriiturc rise ofwittdittgs.

6.6.3 The du~ics rcquircrl IO bc pcrl’ortnctl by three- j)llilSC induc~tiott Illolon 1I;iVC heclt ritliclMlized ittlo

ttinc dill‘crcttt typrs known its Sl In S9 iu IS 12324 : I WI. Any ;rpplica tiott GIII Ix classil~icd inlo OIIC oT the nbnvc duly ly]““.

6.6.4 When the tttotots arc subjcc.~cd to Ircquent slart-

i~lg, the lnsscs which occur durittg Ihe starlittg period lmY~lt1c ;tpprcri;ildc, resulting in 0VcrtIcitling 01 motors. The ~endcnry to fit tuolors of ;I larger rating 1h;ttl ncedcd,jusl to improw itpplicwti0ll is ccrlaitily ttol rccottiiitcttdcd for frequettt sliirliitg.

6.6.5 Frcqucucy revcrsittg by ‘plttggiug’ is even tnorc arduous lliii~t L’rcqucnr slartittg. 011 il l;tppittg timchine IIWS~ ol‘ IIIC cttergy losses ~II the moior occur cluritrg the rcvctsittg period. To nlittituizc thcsc Iosscs the rotor L’itgC is tttadc OfSpCCiill &sign. II is dictt at1 ;IdVatlt;lgC

with frcqueIt1 SlilrliIlg or rcversittg ;Ippli~;tIinns 10 tlsc: it sliprittg nrotor with. perIuaIiciit]y c~otutcclcd CXlCtllilI

‘buffer’ resislancc to 11le rotor circuit. Thus ;I mnsidcr- able proporliott of ~hc losses which would otherwise oc‘cur itt the rotor arc dissip:tM itI the cxtcrnal rcsis- L;IIIW, cwllditlga sm;~ller L‘ra~ue size IO Ix used. Revets-

iug duly motor pernd IIIC clilIIi~>i~lio~t oI’ lnc~hal~irill

clttlch ittld reversing SYSICIIIS.

6.6.6 Closely relatrd IO the prohlctu of starling is the braking of ittductic>n tuobrs. Brake tttotors arc

cmploycd it1 itppliC;lli0ltS wltcrc frcquenl Slilrlillg or

rn4~rsiitg service, illlltlCdiillC ittttl Cx;lCl sloppittg Of mtchiittc IOI~IS or itlslitttt brca hittg Ir s;~lCty rcits(lltS is

rcqttircd.

6.6.7 For ccrtaiu itppli~ittious where peak I(GI~S 01 shorl dttrilliou ;lllt:ru;tlc with periods of light lmd, it is c011i11i01i pmcticc lo ci~ipl~~y Ilywhccl its rcsctvoir 01’ cttcrgy front whidt t11~ pr;t k l(~ild is oblitittd. TIx ~01ttttt~~1iw1 l!Xillll]~lC 0l~lllCSC arc lltc tttc~h;ttiic;tl pro- scs used in lmsscs tool work.

The sudden fo;d which is iIn]mscd WIICII the clulrlt is

ctrg:lg:cd lo lllnl ltlc gcitrittg illtd lorcc dOWI tllC rillll Of

IIIC ]msswould rcquirc ;I very tar&c ttmtnr ifit llywhccl wcrc ttot ittcmrpor;tld. By WIII~ it Ily~h~l, lhc six 01

I]tr itiolor Cilll lx: coitsidcr;tbly rcduccd. ils IIIC ]lyWhCCl

supplim IIIOSI 01 Ihc ])cilk 10;1tl. II\ givitlg SOI~IC 01‘ ifs

hlcmd cttergv lllc* I‘lywhccl hloWS dO\vIt (illlt!tlI IO per-

cctt~) ;III~ durit~g 111r IKW fbw sccc~ntls af’lcr Ihc stroke

ol‘ Ihc press iS co~~~]~lcl~d lhc Iliotor iiccclcriilcs lltc

Ilywhrcl lwck 10 IUII sprccl. l‘hc Ilyvhccl thus IMS lhc cl.ld d’sl~rcxli~tg Ihc Imd OII tlw niolor ovc’r a longer

period. For this duty special tttc,lors arc rcquircd which

dcvclol, ihcir r;tlcd 0UlpUt $11 iIpprOXiIllilt~ly X-IO pcr-

ceitl slip. Thcsc itrc i~t kirgcr fr:imcs ltlilll ttoritt:rI ;ttld

arc fi]U with high exlcmrl ‘Imtfcr’ rcsi5l;tnc.c per’-

In;~ncntly cott~trctrd in Ittc rolor circUi1. Thus IUOSI 01

lhc roIor Iossch iirc dissilxrlud cxlcrrtilllv attd lhc .5i;rc ol

ttt0tor is rcdttrcd.

IS 13555: 1993

6.6.7.1 Flywl~ccls arc sonlctittlcs tnisapplicd to tnarhittcs whose working cycle is so short as to provide

no chance for the ilywhcel to lost spd with the load and rcg;litl it during the rest of the cycle, for exittllple, it ltigh speed rcciprocatit1g press. In such GISCS ;t llywltccl should not Ix used, ottly a tttotor ol’adcquittc oi~lpul is rcronitiicttdcd.

6.7 Mectt-id It~sulaliotls

6.7.1 The cl;rssiIiceti(~u of ittsulalinns on (he ixlsis of

lhcir thcrttt;tl cv;tltt;tfinu is givc~t in ]S 1271 : 19X5. Thcrc has been coIlSider;lhlc changes in clcclric;Il itt- sttl;ilioti in rcccttl yczirs. Sl;llldilrd tii;idtittcs iIrC UStlitlly

CI;ISS B (130°C) or clitss F (IS%), >11td with clilss H (1SO”C) li)r spcci;tl. The mitt devclop~~~c~~ts which

ltavc: givctt rise lo ]~0lCllliill ittcrwsc iii motor tctttpcm- lures arc iii clrclriml slol iusula~ion, including shcrl illsuliltittg IllilICri~lS, slcrviltgs, illl]~rCgttillitlgVilrltislt~s

iltld wiiidiug wire etl;ltncls. As niitcltittc output” ii rc primarily limilcd by Ihc pcmissiblr ~ctttpcmtttr~s itt which their windings ran lx nlxratcd, the t~sc of the

higher tctttpcralurc ittsulatintt cnablcs more c~u~ptit lo bc obt;~incd Irorn a @CII VOIUIHC ofactivr ttlaterial, thitt is, from a givctt Tnttuc.

6.7.2 With t11c dcvclopt~tr~t of production Ittacltittcs

requiring incrcnscd lmvcr (kW) the rttolor spc~ prob ICI11 hilS twmll1c~ sigttil’icattt. Citner;tlly, il tttiichinc lOOI ol’rclalivrly Ihc SiItllC physical size tOdily rqttircs I0 IX

driwtt hy a nlolor of cnttpul (kW) r;tlittg 50 pcrccnl hjghcr 111;1n bcl’orc. Uxr 01. ltighcr Clilss ittsulctliott has Itrlpcd in rcduciiig the fr;intc six iiiitl lhtis ilccotii-

ttiod;tliIig the ttio(or iii rcsIriclcd spac’c.

6.7.3 The ittcrcmcd ;Il~l)IiC;tIi<)tt 01 iIttlOtl);llil)tt iu itt- rlustry hiIS rcsullctl in itI1 incrciisd tlrlll;llld lbr tttntnrs with i’rcqucnt/stop duty cycle. II is ol’lc~t itupo~siblc for

lhe user 10 hilY iii ildVit;KG cX:lc‘lly Wh;ll I]lC Iimlor dtlly cyc]c Itc rcqttircs will bc, with lhc rcxull Ihilt st;tttd;lrtl

tunlors ]lilVC oftctt I’itiled iii sctvicc itflcr a rclafivcll, short period of olm:rtiott. By using Class F ittmlalion OII 111~ st;~nd;~rd tuachincs, Iltcrcforc, tuorc scvc’rc’ Ihrr-

iiiiil slrcssiiig of lhc slator winding mity IX allowed.

The IhCrtttitI 1,h;tr;lctrrisiicX 01‘ CI;ISS F insulation III;I~

l)c tlscd to corisirlcr;ihJc: ildLfilllIil~l~ for iiiolor opcraling urid~~r;il~iiortiiitl ~rl~~~rii~iiig~ottdititrlix such its wick volb

;tgc ilttd frcclitcttcy l~lll~~ltlilliOllS, 1llllXl Ii1 IICC in Sllp]>ly

Vtlllil~C’, Iligll ;Ititl~rcttl tcnq~cri~liircs, ri~hlrkled xttlilii- tiott, lllCCh;lIli(Il ovcrlo;itling. scvcrc’ dttl\, c,yc’lCS sUcl1 ilS I’rrtlttcnl slitrlittg, pr[‘longcd Slilrlitl~, plugging, SIC.

5.X Noise I,evcls

IS 13555: 1993

IS 12OhS : 1987 rovers limits I’0r s0uIld pressure iIlKl exception. The limits ol’ vihratioll Icvcl and the.

soulld power levels oi lhKX-philSC iriduclim motors. mrthods of nmlsurenlcllt have IWCI~ spccificd it1

6.9 Vibt-ation Limits IS 12075 : 1957. TWO classes ol’vibr;ltion ICVC~S ilr(:

Vibratim is houild 10 exist ill i111y rotary sysluli lo ii sl~ccil‘ictl, ON l‘or m)rmal USC ;IIKI the other for

greater or lcsscr rlcgrcc ;tmt the rlcctrir. Iiiotcir is ii0 prccisioil IISC.

IS 13555: 1993

Table 4 Guide for Selection of Induction Motor for Various Applications

C Foreword )

4pplicatiun Type of Motor Recommended Check Points Remrrks

Pump centrifugal Squirrel cage or slipring. Normally started If star-delta starting with open valve is required, >r reciprocating (IS 325 : 1978 and IS 1738 : 1975) with close valve ple,Fe consult motqr manufacturer giving starting

conditions torque requirements.

L’ompressors Rotary Squirrel cage or slipring Unloaded start- In case ‘a squirrel cage niotor is to be used to drive (IS 3’25 : 1978) ing the reciprocaling compressor.

Reciprocating Slipring or squirrel cage Starting with Please consull rllolormanufacturrrgivingstarting (IS 325 : 1976) partial load torque requirement and method of starting.

Eentrifugal fans Squirrel cage or slipring Started with When a squirrel cage motor is uskd, the nccelera- (IS 325 : 197R) cloud chamber lion time should not exceed I.5 seconds on direct-

or closed valves. on-line otherwise please consult motor manufacturers giving value of fan inertia.

3lowcrs Squirrel cage or slipring Starting with When a sctuirrel cage motor is used, the accelera- except 2-pole motors valve closed. rion time on direct on-line starting should not

(IS 325 : 1978) exceed 15 seconds. Otherwise (and also when 2-pole motors are to be used), please consult motor manufacturers giving starting torque rc- quirements and inertia of fans with reference to motor speed.

4gitator and Squirrel cage or slipring Light starling do nixers (for liquids) (IS 325 : 1978) duty

Zranesff Ioists High torque squirrel cage or slipring (IS 325 : 1978)

Pleae furnish the following IO the molar manufacturer : i\ No. of starts, plug stops inching/reversals per

hour. ii) Cyclic duration factor. iii) Method of braking mechanized/Dynamic plug

stop/plug resource. iv) Starting and pullout torque.

1-i fts

Pulley drive

Squirrel cage with smooth uniform acceleration and quiet running.

Squirrel cage or slipring (IS 325 : 1978)

Hell lension

v) Load inertia referred to motor speed.

do

Please furnish the following IO the motor manufacturers : i) Type of Belt, Hat or V Bell and Number ii) Diamekr of pulley on motor shaft iii) Breadth of pulley on motor shaft iv) If the rentre of the hub coincides with the

ccntre of the rim of the pulley. If not, the displacement between the two ccntrrs may be furnished.

v) Weigh1 of pulley in motur side in kg. ’ ? vi) Inclination of pulley system from the\horizon

tal. : ._

VO~IB-_O~ proper &sign of lhc nlofur, it is essential rhar load torque curve and inertia rckrred 10 motor speed are supplied to the m&r

nanufacturer.

IS 13555 : 1993

‘lhble 5 Guide for Selection of Induction Motors tbr Heavy Starting Duty and High Feak Load Applications

( Foreword )

Appliculioo Type of LOWI Special Chnracteristits Type of Motor Hemarks crf Motor -___

14 ne S ha fls Heavy starting Started on load Normal starting High torque squirrel

torque required. 100% FL7 cage or 4ipring ___.~_

lTiL&s

Power mixers do do dU

Flour, l’apcr and I’lcasc furnish lhc following delails tu

Rubber mills Ihc momr manuSaac!urer

Rolling mills

Strokers

i) (.‘omplete luad characteristics

(Zircular saws

iii) Starling and pull-out lorcluc

Pull-out torque 2tI0’6 lo 250 ‘%, High torque squirrel

FL1 C‘age or slipring

iv) Number of starts/stops. inching

and reversal per hyur.

(:rushcrs

(withoul llywheel)

Hammer

mills

(wilhoul t’tywhccl)

v) Melhod ol’hraking. iI any

Hydra-pulpers

Nom- t’or proper design and the motor, it is csscnlial that land torque curve and inertia &erred to motor speed arc suppticd lo ~hr motm

mi~nufaclurrr.

IS 13555 : 1993

IS No.

325 : 197X

1231 : 1974

1271 : 1985

1885 (Part 35) : lY73

2223 : lY83

2254 : 19X.5

ANNEXA ( Clause 2 )

LIST OF REFERRED INDL4N STANDARDS

Titles IS No.

Three-phase induction motor (‘jorrrdl 4691 : 1985 rcwision)

Titles

Degrees of protection provided by enclosures for rotating electrical machinery (‘firirsl revision)

Dimensions of three-phase foot- mounted induction 1110t0rs (t/Ii& 6362 : 1971 rwision)

Designations of methods of cooling for rotating electrical marhincs

Thermal cvaluatiou and classifica- 7538 : 1975 tion of electrical insulation Cfirsf revi.sion)

Three-phase squirrel cage induction umtors for centrifugal pumps for agricultural applicalion

Electrotechnical vocabulary : Part 35 12065 : 1987

Rotating machinery

Permissible limits of noise lcvcl for rotating elcctriral machines

12075 : 1987

Dintensions of flange mounted ac induc- tion motors (second revision)

Mechanical vibration of rotating electri- cal ntachi”nes with shaft height 56 nm and higher-nteasurctttent, evaluations and liiiiits of vibtittion severity

Dimensions of vertical shaft motors for 12824 : 1989 puutps (smnd revison)

Types of duty and classes of ratings as- signed to rotating electrical machines.

a) Linear motion :

ANNEXB (Clause 5.2)

r) Puu1ps :

I’ = g&w) where

F.= useful load in kgf,

V = speed in metres/sccond,

&I = tttechanical cl’ficicn~y of the: drive, and

1 kW = 102 kgf ul/se;ec.

b) Rotary motion :

M x I1

where

M = torque in kgt‘ n = speed in rev/tnin.

p= lOOOxVxSpGrx/~

102Xdfl (kW)

whcrc

V = discharge in i*t3/sccoud

Sp Gr= specific gravity ofthc liquid tn be pumped, and

h = delivery and resistance head in n~wg.

d) Lifts where the rage or cabin weight and halfofthc useful load is usually balanced by rountcrweighls :

p = FxV ~ (kW)

2 x 102 x CT”

where

F = useful load in kgi, and

V = speeds in ut/scc.

11

IS 13555 : 1993

c) Faus :

p= vxp 102 x ($6

(kW)

where

V = air delivery iu m3/sec

P = air pressure in kgl’/u? (mwg) at the outlet.

Vary& duties S3 and S6 (s.L’~ IS 12824 : 1989) where the losses occurring duriug slartiug arc negli- gible, the equivalent Sl rating load miy, therefore, be expressed as a root umu square kW oulpul, or

kW (rms) = /

(kW1)” tl + (kW2)‘fz 11”

Kf” + l1 + I, + . . . . . . . . . . . . . . . . . J

where

kW (rnls) = equivalrnt Sl load

kW1 = cquivalcnt kW in first interval of duty cycle, carried tbr time I I,

I l+tl = tolal duty cycle tiuic iu secoutls,

K = rous~an1 for duly cycle time a1 zero speed which is a ppmx, l/4 for TEFC motors (cooling lC41 as IJer IS 6362 : 1971), it nd l/3 for opcu omtors (Cooling ICOl as per IS 6362 : 1971); and

‘(1 = lime of duly cycle ol‘ zero speed.

12

Standard Mark The use of the Standard Mark is governed by the provisions of the tlurrau qf Zn&un

Standards Act, 1986 and the Rules and Regulations made thereunder. The Standard Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, testing and quality control which is devised and supervised by BTS and operated by the producer. Standard marked products are also continuously checked by BIS for con- formity to that standard as a further safeguard. Details of conditions under ~lhich ;1 licrncr for the use of the Standard Mark may be granted to mauufacturers or producers may be obtained from the Bureau of Indian Standards.

Bureau of Indian Standards

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

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced m any form without the prior permission in writing of BIS. This does not preclude the free use, in the course of implementing 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 any reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of ‘BIS Handbook’ and ‘Standards Monthly Additions’. Comments on this Indian Standard may be sent to BIS giving the following reference:

Dot : No. ET 1.5 ( 3140)

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

RUREAU OF INDIAN STANDARDS

Headquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telephones : 331 01 31, 331 13 75

Regional Offices :

Central : Marx& Bhavan, 9 Bahadur Shah Zafar Marg NEW DELHI 110002

Eastern : l/ 14 C. I. T. Scheme VT1 M, V. I. P. Road, Maniktola CALCUTTA 700054

Northern : SC0 445-446, Sector 35-C, CHANDIGARH 160036

Telegrams : Manaksanstha ( Commoli to all offices )

Telephone

1

331 01 31 331 13 75

i

37 84 99, 37 85 61 37 86 26, 37 86 62

1

53 38 43, 53 16 40 53 23 84

Southern : C. J. T. Campus, IV Cross Road, MADRAS 600113

1

235 02 16, 235 04 42 235 15 19, 235 23 15

Western : Manakalaya, E9 MIDC, Marol, Andheri ( East ) BOMBAY 400093

632 92 95, 632 78 58 632 78 91, 632 78 92

Branches : AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE. FARIDABAD. GHAZIAUAD. GUWAHATT. HYDEKARAJ).

JATPUR. KANPUR. T.UCKNOW. PATNA. Tf~TK’lJVANANTtiAI’~IIIAM.