1、Copyright 1998 IEEE All Rights Reserved 1IEEE Std 295-1969 (R2007)IEEE Standard for Electronics Power TransformersReaffirmed 5 December 2007IEEE-SA Standards BoardPublished by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017,USAiiFOREWORDThe Electro
2、nics Transformer Technical Committee for several years has been working towards the generation of aStandard for electronics purpose power transformers even while under AIEE auspices. Earlier attempts seemed toparallel the distribution and power transformer Standards too closely, and hence missed the
3、 point of departure of howelectronics transformers needed, at least in part, a different, treatment than power distribution transformer Standards.After the completion of the Wide-Band Standards Nos. 111 and 264 by the committee, a pattern was established thatcould be followed in the Power Transforme
4、r Standard to achieve the desired results. This proposed Standard can bewell considered to be the product of the merger of AIEE and IRE people into the new blend of IEEE as it representsconcessions oil the part of each to the other at various points.Some interesting problems had to be resolved in th
5、e process. For example, in the use of solid-state rectiers it isnecessary to provide fast and sensitive protection for the easily destroyed diodes in the event of faulting. This, in turn,led to a new denition of transformer inrush current, which we found was not previously dened satisfactorily. Also
6、,the extensive use of combined alternating and direct voltages and currents in electronics transformers made itnecessary to resolve certain insulation testing problems that have plagued the industry for years. Yet to say that theseproblems are resolved is an oversimplication of the situation. Nevert
7、heless, a good start has been made in this regard.We have attempted to give guidance and direction in the sensitive area of corona testing without foreclosing on theadoption of new Standards and understandings on the subject.For all sizes of electronics purpose power transformers, it is expected tha
8、t this Standard will supersede the use of USAC57 Standards.PURPOSEThe character and applications of transformers used in electronic circuits are enough different from other categories sothat none of the existing Standards does a satisfactory job. Much confusion and conict has obtained in the past se
9、veralyears because of this lack, with different people having a wide variety of opinion relative to many aspects ofspecication and testing.This Standard is intended to control by exception in the areas where conict and disagreement have been mostnoticeable. Other well-known Standards are listed that
10、 should be used in areas where general agreement exists.iiiACKNOWLEDGMENTThe Institute wishes to acknowledge its indebtedness to those who have so freely given of their time and knowledge,and have conducted experimental work on which many of the IEEE publications are based.This publication was prepa
11、red by the Electronics Power Transformer Subcommittee of the Electronics TransformersCommittee of the IEEE Parts, Materials, and Packaging Group. The membership of the Subcommittee was:W. W. Wahlgren, Chair G. D. Polzin, Secretary E. E. Aldrich (deceased), Secretary C. E. Carter, Jr.W. J. FieldS. Ha
12、nnonA. D. HasleyO. KiltieL. W. KirkwoodA. J. KornbluhR. LeeH. W. LordH. MitsanasT. PelcI. TarrH. I. TillingerA. B. TrussellJ. P. WhistlerD. WildfeuerR. G. Wolpert Copyright 1969 by The Institute of Electrical and Electronics Engineers, Inc.ivCLAUSE PAGE1. SCOPE 11.1 Related and Reference Standards.
13、12. DEFINITIONS22.1 Additional Definitions 23. SYMBOLS34. TRANSFORMER ELECTRICAL TESTS.34.1 Electrical Tests. 34.2 Characteristic Tests 35. ELECTRICAL TESTS .35.1 Electrical Strength Tests 35.2 Induced Voltage Tests 45.3 Repeated Electric Strength Testing 55.4 Corona Tests 55.5 Corona Test Methods .
14、 65.6 Temperature Rise Tests 6Annex I Definitions Relating to Transformer-Rectifier Systems (Informative).8Annex II Transformer Terminal Marking Guide (Informative)9Annex III Typical Norms and Tolerances for Transformer Specifications (Informative)13Annex IV Electric Strength Tests for Transformers
15、Connected to High-Voltage Lines (Informative)14Annex V Inrush Current Considerations (Informative) 16Annex VI Service Conditions (Informative).17Copyright 1969 IEEE All Rights Reserved1IEEE Standard for Electronics Power Transformers1. SCOPEThis Standard pertains to power transformers and inductors
16、that are used in electronic equipments and supplied bypower lines or generators of essentially sine wave or polyphase voltage. Guides to application and test procedures areincluded. Appendices contain certain precautions, recommended practices, and guidelines for typical values. Provisionis made for
17、 relating the characteristics of transformers to the associated rectiers and circuits.Certain pertinent denitions relating to transformers and transformer applications, which have not been foundelsewhere, are included with appropriate discussion. Attempts are made to alert the industry and professio
18、n to factorsthat are commonly overlooked.This Standard includes, but is not limited to, the following specic transformers and inductors.Rectier supply transformers for either high- or low-voltage supplies.Filament and cathode heater transformers.Transformers for alternating current resonant charging
19、 circuits.Inductors used in rectier lters.Autotransformers with xed taps.1.1 Related and Reference Standardsa) USA Standard C57: Transformers, Regulators and Reactors.USA Standard C57: 12.001965, General.USA Standard C57: 12.201964, Overhead-TypeDistribution Transformers, 67 000 Volts and Below, 500
20、 kVA and Smaller.USA Standard C57: 12.801958, Terminology.USA Standard C57: 12.901965, Test Code.USA Standard C57: 181964, Pool-Cathode Mercury-Arc Rectier Transformers, Requirements,Terminology and Test Code.USA Standard C57: 311948, Guide for Operation of Transformers at Altitudes Greater Than 100
21、0 Meters.USA Standard C57: 321948, Guide for Operation of Transformers, Regulators and Reactors.b) USA Standard C42.USA Standard C42.251956, Denitions of Electrical Terms (Industrial Control Equipment).USA Standard C42.651957, Denitions of Electrical Terms (Communications).2Copyright 1969 IEEE All R
22、ights ReservedIEEE Std 295-1969 IEEE STANDARD FORc) IEEE Standards Publication No. 111, Low-Power Wide-Band Transformers.d) IEEE Standards Publication No. 264, High-Power Wide-Band Transformers.e) Standards in Preparation.Corona Test Guide.2. DEFINITIONSElectrical terms used in this Standard shall b
23、e in accordance with those given in USA Standard C42 AmericanStandard Denitions of Electrical Terms insofar as they apply except as herein stated.The IEEE Dictionary, when issued, shall be applicable and included as a part of this Standard and shall takeprecedence over USA Standard C42 in case of co
24、nict.2.1 Additional Definitions2.1.1 Turns Ratio: shall be preferably dened in terms of the primary turns as the number of turns of a givensecondary divided by the number of primary turns. Thus a ratio less than one (1) is a step-down transformation, a ratiogreater than one (1) is a step-up transfor
25、mation, and a ratio equal to one (1) is unity ratio.2.1.2 Loaded Voltage Ratio: shall be equal to the secondary voltage divided by the primary voltage. (See paragraph2.1.1.) For linear loads, the ratio shall be stated for a specied load current and power factor. For rectier loads, theratio should be
26、 given for the specied circuit conguration, including the lters, and the rated direct-current load.Unless otherwise stated, the ratio shall be given for rated conditions, line voltage, frequency, load, and stabilizedtemperature. Primary voltages shall be given as line to line and secondary voltages
27、as leg values (terminal to neutral orcenter tap if used) unless otherwise indicated.2.1.3 No-Load Loss: (excitation loss) is the input power, expressed in watts, to a completely assembled transformerthat is excited at rated terminal voltage and frequency, but not supplying load current.2.1.4 Full-Lo
28、ad Losses: 2.1.4.1 Core Loss: is the measured power loss, expressed in watts, attributable to the material in the core andassociated clamping structure, of a transformer that is excited, with no connected load, at a core ux density andfrequency equal to that in the core when rated voltage and freque
29、ncy is applied and rated load current is supplied.2.1.4.2 Winding Loss: (copper loss) is the power losses of all windings involved, expressed in watts, in an inductor ortransformer with the values measured at or corrected to the rated load current, frequency, and waveshape an stabilizedat the maximu
30、m ambient temperature.2.1.4.3 Stray Losses: are those occurring in the core and case structure that result from the leakage ux and stray uxof a transformer when supplying rated load current.2.1.5 Graded Insulation: is the selective arrangement of the insulation components of a composite insulation s
31、ystemto more nearly equalize the voltage stresses throughout the insulation system2.1.6 Inrush Current: is the maximum root-mean-square or average current value, determined for a specied interval,resulting from the excitation of the transformer with no connected load, and with essentially zero sourc
32、e impedance,and using the minimum primary turns tap available and its rated voltage. (See Annex V.)2.1.7 Peak Inrush Current: is the peak instantaneous current value resulting from the excitation of the transformerwith no connected load, and with essentially zero source impedance, and using the mini
33、mum turns primary tap andrated voltage.2.1.8 Essentially Zero Source Impedance: implies that the source impedance is low enough so that the test currentsunder consideration would cause less than ve (5) percent distortion (instantaneous) in the voltage amplitude orwaveshape at the load terminals. (Se
34、e Annex V.)Copyright 1969 IEEE All Rights Reserved3ELECTRONICS POWER TRANSFORMERS IEEE Std 295-19693. SYMBOLSThe proposed IEEE Standards Publication No. 276 Letter and Graphic Symbols for Electronics Transformers orrevisions shall apply.4. TRANSFORMER ELECTRICAL TESTSTransformer terminals normally g
35、rounded in service should be grounded during these tests or connected as otherwiserequired or noted in the following test description.4.1 Electrical Tests(values not recorded) It is recommended that the following electrical tests be made on all transformers.Ratio, polarity, terminal marking tests.No
36、-load excitation; exciting current (amperes), loss (watts).Corona test (when specied).Induced voltage.Electric strength of insulation.4.2 Characteristic Tests(may be performed on a limited basis unless otherwise specied).Inrush current (when specied).Winding loss, impedance, regulation.Leakage induc
37、tance.Impulse (when specied).Temperature rise, winding resistance.5. ELECTRICAL TESTS5.1 Electrical Strength Tests(see paragraph 5.3 for retesting). Applied high-voltage tests to major insulation systems should be made with windingsshorted. Windings and shields on one side of the insulation should b
38、e connected to frame and ground while windingsor shields on the other side should be connected together. Sine wave test voltages having a frequency in the operatingrange of the transformer and having adequate current capacity for the application is applied between the two sets ofterminals in the man
39、ner set forth herein. All voltages should be dened in the same terms; e.g., root mean square, peak,average.5.1.1 Method Voltageshould be increased at a convenient uniform rate of not greater than 2000 volts per second, from zero to the speciedvalue, maintained for the specied period (unless breakdow
40、n occurs) then decreased to zero at the same rate.4Copyright 1969 IEEE All Rights ReservedIEEE Std 295-1969 IEEE STANDARD FOR5.1.2 Primary Windingswith rated voltagex over600 volts line to line should be tested in accordance with USAS C57.12 as amended or revised(see Annex IV).5.1.3 Primary Windings
41、with rated voltages 600 volts or lessline to line should be tested with sine wave alternating voltage equal to twice therated voltage of the highest voltage tap, plus 1000 volts and held at that value for the duration of 3600 cycles.5.1.4 Connectionsfor windings not under test should be specied so t
42、hat unwarranted stresses will not occur during the electric strengthtests. Windings with relatively low working voltage to ground should be grounded during the test of other windings toprevent the lower voltage insulation from being damaged through capacitive coupling.5.1.5 Secondary Windingsthat ha
43、ve no special test voltage specied should be tested with applied alternating voltage equal to twice the ratedvoltage of the highest voltage tap, plus 1000 volts and held at that value for the lesser time of 3600 cycles or oneminute.5.1.6 Secondary Windings or Inductor Windingsthat may have a specic
44、operating direct or alternating voltage derived elsewhere, unless otherwise specied, shouldbe tested at twice the working volts plus 1000 volts for the lesser of one minute or 3600 cycles and using the same typeand frequency of voltage as the working stress. High alternating voltage should not be su
45、bstituted for direct currentunless specically authorized by the manufacturer.5.1.7 When the voltage insulation strength is not the same at both ends of a winding, an induced voltage test may besubstituted in lieu of the applied voltage test.5.2 Induced Voltage Tests5.2.1 Secondary Windings and Induc
46、torsemploying graded insulation systemsmay be tested as described herein in lieu of other high-voltage electric strengthtests.NOTE Many high-voltage rectier windings have a distinctly different voltage stress to adjacent windings on one end of awinding when compared with the stress on the other end.
47、 Not only can the voltage stress be different in magnitude, butalso in waveform. An alternating voltage stresses the insulation much more than a direct voltage of the same peak value.For example, a three-phase winding wye connected for a system using three-phase bridge rectier will have a directvolt
48、age to ground at the neutral equal to one-half of the bridge output, whereas the rectier terminals will have analternating voltage excursion from zero to twice the peak voltage of one leg. It is not necessary or desirable to use thesame kind and amount of insulation at the neutral as at the rectier
49、terminals, yet it is desirable to test both insulationsat twice the normal working voltage and with a waveform similar to that of the working voltage. In thistest, apply adirect voltage between neutral and ground equal to twice the working voltage of the neutral, and at the same time excitethe transformer windings with a voltage equal to twice the normal induced voltage, thus placing a double voltage stressin kind at each major insulation interface, and at the same time check out the intrawinding withstand capability.
