1、The Institute of Electrical and Electronics Engineers, Inc.345 East 47th Street, New York, NY 10017-2394, USACopyright 1996 by the Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Published 1996. Printed in the United States of America.ISBN 1-55937-751-8No part of this pub
2、lication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.IEEE Std 620-1996 (R2008)IEEE Guide for the Presentation ofThermal Limit Curves for SquirrelCage Induction MachinesSponsorElectric Machinery Committeeof theIE
3、EE Power Engineering SocietyReaffirmed 10 December 2008Approved 20 June 1996IEEE-SA Standards BoardAbstract: Thermal limit curves for induction machines are defined. A procedure is established forthe presentation of these curves, and guidance for the interpretation and use of these curves formachine
4、 thermal protection is provided.Keywords: machine thermal protection, rotor cage windings, stator cage windings, thermal limitcurves, three-phase squirrel cage induction machinesAuthorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrict
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17、ejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrictions apply.iiiIntroduction(This introduction is not part of IEEE Std 620-1996, IEEE Guide for the Presentation of Thermal Limit Curves forSquirrel Cage Induction Machines.)This revision of IEEE Std 620-1987 was initiated by the I
18、nduction Machinery Subcommittee of the ElectricMachinery Committee of Power Engineering Society. The standard was originally issued in 1981 for trial-use only and had expired. Further, it was felt that the revised standard of 1987 needed to be issued as a guide.The following is a list of participant
19、s in the Working Group: Nirmal K. Ghai,ChairAt the time IEEE Std 620-1996 was balloted, the Induction Machinery Subcommittee had the followingmembership:Nirmal K. Ghai,ChairThe following persons were on the balloting committee:Michael J. CostelloJames H. DymondJonathan D. GardellFranklin H. GroomsJa
20、mes R. MichalecNils E. NilssonJames OliverLloyd W. BuchananStanley S. BurnsDouglas H. CashmoreC. C. ChanJack L. CraggsJan A. DeKockPaul DiamantJames H. DymondSteve EiringRay FindlayPaul C. GabersonFranklin H. GroomsRobert J. HarringtonJohn HsuThomas A. HigginsHoward E. JordanJ. Glen KarolyiJames A.
21、Kirtley, JrSian H. LieThomas A. LipoWalter J. MartinyNigel P. McQuinEdward J. MichaelsJames R. MichalecNils E. NilssonPaul I. NippesDonald W. NovotnyChee-Mung OngEdward L. OwenPragasen PillayMichel PoloujadoffM. A. RahmanRandy R. SchoenA. M. SharafJan SteinBarna SzabadosLarry WallStanley S. BurnsDou
22、glas H. CashmoreC. C. ChanJack L. CraggsMichael J. CostelloJan A. DeKockJames H. DymondPaul C. GabersonJonathan D. GardellNirmal K. GhaiFranklin H. GroomsRobert J. HarringtonThomas A. HigginsJohn HsuThomas A. LipoWalter J. MartinyEdward J. MichaelsJames R. MichalecNils E. NilssonJames A. OliverParag
23、asen PillayM. Azizur RahmanRandy R. SchoenJan SteinAuthorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrictions apply.ivWhen the IEEE Standards Board approved this standard on 20 June 1996, it had the following membership:Donald C. Lo
24、ughry,ChairRichard J. Holleman,Vice ChairAndrew G. Salem,Secretary*Member EmeritusAlso included are the following nonvoting IEEE Standards Board liaisons:Satish K. AggarwalAlan H. CooksonChester C. TaylorLisa S. YoungIEEE Standards Project EditorGilles A. BarilClyde R. CampJoseph A. CannatelliStephe
25、n L. DiamondHarold E. EpsteinDonald C. FleckensteinJay Forster*Donald N. HeirmanBen C. JohnsonE. G. “Al” KienerJoseph L. Koepfinger*Lawrence V. McCallL. Bruce McClungMarco W. MigliaroMary Lou PadgettJohn W. PopeJose R. RamosArthur K. ReillyRonald H. ReimerGary S. RobinsonIngo RschJohn S. RyanChee Ki
26、ow TanLeonard L. TrippHoward L. WolfmanAuthorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrictions apply.vContentsCLAUSE PAGE1. Overview 11.1 Purpose. 11.2 Scope 12. Thermal overloads . 22.1 Causes 22.2 Effects 22.3 Thermal limit cur
27、ve 23. Presentation 43.1 Dependent variables. 43.2 Current scale 43.3 Time scale 43.4 Conditions represented. 43.5 Acceleration curve . 43.6 Curves at multiple voltages 43.7 Additional information. 54. Application. 54.1 Caution. 54.2 Starting from reverse rotation 54.3 Margins 55. Bibliography 6Auth
28、orized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrictions apply.1IEEE Guide for the Presentation of Thermal Limit Curves for Squirrel Cage Induction Machines1. Overview1.1 PurposeThis guide defines thermal limit curves for induction ma
29、chines, establishes a standard procedure for thepresentation of these curves, and provides guidance for the interpretation and use of these curves formachine thermal protection.1.2 ScopeThis guide applies to three-phase squirrel cage induction machines, 250 hp (200 kW) and above. It isintended to be
30、 used for machines designed for specified load and application conditions. However, it mayalso be used for smaller, general purpose machines if application and load conditions are specified.CAUTIONThe portion of the thermal limit curves dealing with locked rotor and running overloadconditions applie
31、s to all applications for a given machine. The acceleration portion of thecurves when requested can be provided only if the user supplies load inertia (Wk2), theload speed-torque curve, and the starting voltage.Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at
32、 11:19 from IEEE Xplore. Restrictions apply.IEEEStd 620-1996 IEEE GUIDE FOR THE PRESENTATION OF THERMAL LIMIT CURVES22. Thermal overloads2.1 CausesThe stator and rotor cage windings of a squirrel cage induction machine may exceed design temperaturesdue to a number of reasons, some of which are as fo
33、llows:a) The machine may lock up, i.e., remain at zero speed with voltage applied to the stator winding, asmight happen in the case of low starting voltage and/or mechanical malfunction.b) The machine may start but fail to accelerate to its running speed, due to inadequate accelerating torqueat some
34、 speed lower than the breakdown torque point, causing it to run at that subsynchronous speed.c) The machine may be overloaded continuously at close to its operating speed.Under the locked-rotor condition, there is normally no ventilation, and the heat loss from the windings is byconduction and radia
35、tion. During acceleration, depending on the speed, the heat loss is both by conductionand by the ventilating effect of air movement. During running overloads, the normal ventilation of themachine is the primary mode of cooling.2.2 EffectsUnder locked rotor conditions, the current in the windings is
36、4 to 8 times the rated full-load current, and thestator winding losses are approximately 16 to 64 times the rated losses. The rotor losses are higher still at highslip values because of the increase in rotor resistance due to skin effect. Up to the breakdown torque pointduring acceleration, the curr
37、ent reduces somewhat in magnitude from the locked rotor value as the machineaccelerates, but it is still many times the rated value. The stator and rotor losses are therefore high during theacceleration period. The temperatures of the stator and rotor cage windings therefore rise rapidly during thel
38、ocked-rotor and acceleration conditions. The current can be maintained at any of these high values for briefperiods until the winding temperatures reach values beyond which insulation, and/or winding damage, couldoccur. At running conditions, the overloads can be maintained for relatively longer per
39、iods of time dependingon individual designs, since the currents are not as high as during starting and acceleration. Some motor lossof life is, however, experienced with each overload exceeding the thermal limit.A knowledge of the length of safe operating time for each one of these overcurrent condi
40、tions is necessary ifprotection against damage due to over-temperatures is to be provided. Thermal limit curves are the vehiclefor providing such information.2.3 Thermal limit curveA thermal limit curve is a plot of the maximum permissible safe time versus line current in the windings ofthe machine
41、under conditions other than normal operation. It represents the following three situations:a) Locked rotorb) Starting and accelerationc) Running overloadThe complete curve, representative of these three conditions for the winding (stator or rotor) with theshortest safe time, may be discontinuous and
42、 may consist of up to three segments (see figure 1).The thermal limit curve is intended to be used in conjunction with the machine time-current curve for anormal start to set the machine protective devices for the thermal protection of the machine during startingand running conditions. The machine t
43、ime-current curves, when available, are presented on the same plot asthe thermal limit curves.Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrictions apply.IEEEFOR SQUIRREL CAGE INDUCTION MACHINES Std 620-19963Figure 1Typical the
44、rmal limit curves per IEEE 620-1996Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on July 16, 2009 at 11:19 from IEEE Xplore. Restrictions apply.IEEEStd 620-1996 IEEE GUIDE FOR THE PRESENTATION OF THERMAL LIMIT CURVES43. Presentation3.1 Dependent variablesThe thermal limit cur
45、ve shall be drawn with current as a percentage of the machine rated full-load currentagainst the safe time in seconds.3.2 Current scaleThe current shall be plotted as the abscissa on a linear scale.3.3 Time scaleTime shall be plotted as the ordinate on a multicycle logarithmic scale.3.4 Conditions r
46、epresentedThe curve shall represent the following three conditions:a) From approximately 60% of the locked rotor current to the rated locked rotor current, a safe lockedrotor thermal capability curve shall be drawn that indicates the maximum length of time which themachine can stay locked without da
47、mage.b) From the current at locked rotor to approximately the current at the breakdown torque point, a curverepresenting the thermal capability during acceleration shall be drawn.c) From approximately the rated full-load current (or current at service factor load for motors withservice factors) to c
48、urrent at approximately the breakdown torque, a motor running overload thermalcapability curve shall be drawn.The thermal limit curve may be continuous when a single curve adequately represents the data, or may bediscontinuous with one or two breaks if necessary.The thermal limit curves shall repres
49、ent two initial conditions: the machine initially at ambient temperature,and the machine initially at the rated load operating temperature.3.5 Acceleration curveThe motor acceleration time-current curve shall be plotted on the same graph as the thermal limit curve.3.6 Curves at multiple voltagesWhen the motor is designed for starting at a voltage or voltages lower than the rated voltage, the thermallimit and the acceleration time-current curves shall be drawn for the rated voltage and for each of the lowervoltages. These curves may be drawn on a single graph or on a series of graphs, one
