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1、Copyright 1998 IEEE All Rights Reserved1 IEEE Std 295-1969 (R2007) IEEE Standard for Electronics Power Transformers Reaffirmed 5 December 2007 IEEE-SA Standards Board Published by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA ii FOREWORD The
2、 Electronics Transformer Technical Committee for several years has been working towards the generation of a Standard for electronics purpose power transformers even while under AIEE auspices. Earlier attempts seemed to parallel the distribution and power transformer Standards too closely, and hence
3、missed the point of departure of how electronics 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 that could be followed in the Pow
4、er Transformer Standard to achieve the desired results. This proposed Standard can be well considered to be the product of the merger of AIEE and IRE people into the new blend of IEEE as it represents concessions oil the part of each to the other at various points. Some interesting problems had to b
5、e resolved in the process. For example, in the use of solid-state rectiers it is necessary 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 sa
6、tisfactorily. Also, the extensive use of combined alternating and direct voltages and currents in electronics transformers made it necessary to resolve certain insulation testing problems that have plagued the industry for years. Yet to say that these problems are resolved is an oversimplication of
7、the situation. Nevertheless, 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 the adoption of new Standards and understandings on the subject. For all sizes of electronics purpose power transfor
8、mers, it is expected that this Standard will supersede the use of USA C57 Standards. PURPOSE The character and applications of transformers used in electronic circuits are enough different from other categories so that none of the existing Standards does a satisfactory job. Much confusion and conict
9、 has obtained in the past several years because of this lack, with different people having a wide variety of opinion relative to many aspects of specication and testing. This Standard is intended to control by exception in the areas where conict and disagreement have been most noticeable. Other well
10、-known Standards are listed that should be used in areas where general agreement exists. iii ACKNOWLEDGMENT The 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
11、are based. This publication was prepared by the Electronics Power Transformer Subcommittee of the Electronics Transformers Committee 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 ) ,
12、 Secretary C. E. Carter, Jr. W. J. Field S. Hannon A. D. Hasley O. Kiltie L. W. Kirkwood A. J. Kornbluh R. Lee H. W. Lord H. Mitsanas T. Pelc I. Tarr H. I. Tillinger A. B. Trussell J. P. Whistler D. Wildfeuer R. G. Wolpert Copyright 1969 by The Institute of Electrical and Electronics Engineers, Inc.
13、 iv CLAUSEPAGE 1. SCOPE1 1.1 Related and Reference Standards. 1 2. DEFINITIONS2 2.1 Additional Definitions 2 3. SYMBOLS3 4. TRANSFORMER ELECTRICAL TESTS.3 4.1 Electrical Tests. 3 4.2 Characteristic Tests 3 5. ELECTRICAL TESTS .3 5.1 Electrical Strength Tests 3 5.2 Induced Voltage Tests 4 5.3 Repeate
14、d Electric Strength Testing 5 5.4 Corona Tests 5 5.5 Corona Test Methods. 6 5.6 Temperature Rise Tests 6 Annex I Definitions Relating to Transformer-Rectifier Systems (Informative).8 Annex II Transformer Terminal Marking Guide (Informative)9 Annex III Typical Norms and Tolerances for Transformer Spe
15、cifications (Informative)13 Annex IV Electric Strength Tests for Transformers Connected to High-Voltage Lines (Informative)14 Annex V Inrush Current Considerations (Informative)16 Annex VI Service Conditions (Informative).17 Copyright 1969 IEEE All Rights Reserved 1 IEEE Standard for Electronics Pow
16、er Transformers 1. SCOPE This Standard pertains to power transformers and inductors that are used in electronic equipments and supplied by power lines or generators of essentially sine wave or polyphase voltage. Guides to application and test procedures are included. Appendices contain certain preca
17、utions, recommended practices, and guidelines for typical values. Provision is made for relating the characteristics of transformers to the associated rectiers and circuits. Certain pertinent denitions relating to transformers and transformer applications, which have not been found elsewhere, are in
18、cluded with appropriate discussion. Attempts are made to alert the industry and profession to factors that 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. Fi
19、lament and cathode heater transformers. Transformers for alternating current resonant charging circuits. Inductors used in rectier lters. Autotransformers with xed taps. 1.1 Related and Reference Standards a)USA Standard C57: Transformers, Regulators and Reactors. USA Standard C57: 12.001965, Genera
20、l. USA Standard C57: 12.201964, Overhead-Type Distribution Transformers, 67 000 Volts and Below, 500 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 a
21、nd Test Code. USA Standard C57: 311948, Guide for Operation of Transformers at Altitudes Greater Than 1000 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 Eq
22、uipment). USA Standard C42.651957, Denitions of Electrical Terms (Communications). 2 Copyright 1969 IEEE All Rights Reserved IEEE Std 295-1969IEEE STANDARD FOR c)IEEE Standards Publication No. 111, Low-Power Wide-Band Transformers. d)IEEE Standards Publication No. 264, High-Power Wide-Band Transform
23、ers. e)Standards in Preparation. Corona Test Guide. 2. DEFINITIONS Electrical terms used in this Standard shall be in accordance with those given in USA Standard C42 American Standard Denitions of Electrical Terms insofar as they apply except as herein stated. The IEEE Dictionary, when issued, shall
24、 be applicable and included as a part of this Standard and shall take precedence over USA Standard C42 in case of conict. 2.1 Additional Definitions 2.1.1 Turns Ratio: shall be preferably dened in terms of the primary turns as the number of turns of a given secondary divided by the number of primary
25、 turns. Thus a ratio less than one (1) is a step-down transformation, a ratio greater than one (1) is a step-up transformation, 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 paragraph 2.1.1.) For
26、linear loads, the ratio shall be stated for a specied load current and power factor. For rectier loads, the ratio should be 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
27、voltage, frequency, load, and stabilized temperature. Primary voltages shall be given as line to line and secondary voltages as leg values (terminal to neutral or center tap if used) unless otherwise indicated. 2.1.3 No-Load Loss: (excitation loss) is the input power, expressed in watts, to a comple
28、tely assembled transformer that is excited at rated terminal voltage and frequency, but not supplying load current. 2.1.4 Full-Load Losses: 2.1.4.1 Core Loss: is the measured power loss, expressed in watts, attributable to the material in the core and associated clamping structure, of a transformer
29、that is excited, with no connected load, at a core ux density and frequency equal to that in the core when rated voltage and frequency 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 o
30、r transformer with the values measured at or corrected to the rated load current, frequency, and waveshape an stabilized at the maximum 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 ux of a transformer when sup
31、plying rated load current. 2.1.5 Graded Insulation: is the selective arrangement of the insulation components of a composite insulation system to more nearly equalize the voltage stresses throughout the insulation system 2.1.6 Inrush Current: is the maximum root-mean-square or average current value,
32、 determined for a specied interval, resulting from the excitation of the transformer with no connected load, and with essentially zero source 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 curren
33、t value resulting from the excitation of the transformer with no connected load, and with essentially zero source impedance, and using the minimum turns primary tap and rated voltage. 2.1.8 Essentially Zero Source Impedance: implies that the source impedance is low enough so that the test currents u
34、nder consideration would cause less than ve (5) percent distortion (instantaneous) in the voltage amplitude or waveshape at the load terminals. (See Annex V.) Copyright 1969 IEEE All Rights Reserved 3 ELECTRONICS POWER TRANSFORMERSIEEE Std 295-1969 3. SYMBOLS The proposed IEEE Standards Publication
35、No. 276 Letter and Graphic Symbols for Electronics Transformers or revisions shall apply. 4. TRANSFORMER ELECTRICAL TESTS Transformer terminals normally grounded in service should be grounded during these tests or connected as otherwise required or noted in the following test description. 4.1 Electr
36、ical Tests (values not recorded) It is recommended that the following electrical tests be made on all transformers. Ratio, polarity, terminal marking tests. No-load excitation; exciting current (amperes), loss (watts). Corona test (when specied). Induced voltage. Electric strength of insulation. 4.2
37、 Characteristic Tests (may be performed on a limited basis unless otherwise specied). Inrush current (when specied). Winding loss, impedance, regulation. Leakage inductance. Impulse (when specied). Temperature rise, winding resistance. 5. ELECTRICAL TESTS 5.1 Electrical Strength Tests (see paragraph
38、 5.3 for retesting). Applied high-voltage tests to major insulation systems should be made with windings shorted. Windings and shields on one side of the insulation should be connected to frame and ground while windings or shields on the other side should be connected together. Sine wave test voltag
39、es having a frequency in the operating range of the transformer and having adequate current capacity for the application is applied between the two sets of terminals in the manner set forth herein. All voltages should be dened in the same terms; e.g., root mean square, peak, average. 5.1.1 Method Vo
40、ltage should be increased at a convenient uniform rate of not greater than 2000 volts per second, from zero to the specied value, maintained for the specied period (unless breakdown occurs) then decreased to zero at the same rate. 4 Copyright 1969 IEEE All Rights Reserved IEEE Std 295-1969IEEE STAND
41、ARD FOR 5.1.2 Primary Windings with rated voltagex over 600 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 with rated voltages 600 volts or less line to line should be tested with sine wave alternating voltage equal to
42、twice the rated voltage of the highest voltage tap, plus 1000 volts and held at that value for the duration of 3600 cycles. 5.1.4 Connections for windings not under test should be specied so that unwarranted stresses will not occur during the electric strength tests. Windings with relatively low wor
43、king voltage to ground should be grounded during the test of other windings to prevent the lower voltage insulation from being damaged through capacitive coupling. 5.1.5 Secondary Windings that have no special test voltage specied should be tested with applied alternating voltage equal to twice the
44、rated voltage of the highest voltage tap, plus 1000 volts and held at that value for the lesser time of 3600 cycles or one minute. 5.1.6 Secondary Windings or Inductor Windings that may have a specic operating direct or alternating voltage derived elsewhere, unless otherwise specied, should be teste
45、d at twice the working volts plus 1000 volts for the lesser of one minute or 3600 cycles and using the same type and frequency of voltage as the working stress. High alternating voltage should not be substituted for direct current unless specically authorized by the manufacturer. 5.1.7 When the volt
46、age insulation strength is not the same at both ends of a winding, an induced voltage test may be substituted in lieu of the applied voltage test. 5.2 Induced Voltage Tests 5.2.1 Secondary Windings and Inductors employing graded insulation systems may be tested as described herein in lieu of other h
47、igh-voltage electric strength tests. NOTE Many high-voltage rectier windings have a distinctly different voltage stress to adjacent windings on one end of a winding when compared with the stress on the other end. Not only can the voltage stress be different in magnitude, but also in waveform. An alt
48、ernating 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 direct voltage to ground at the neutral equal to one-half of the bridge output, whereas the rect
49、ier terminals will have an alternating voltage excursion from zero to twice the peak voltage of one leg. It is not necessary or desirable to use the same kind and amount of insulation at the neutral as at the rectier terminals, yet it is desirable to test both insulations at twice the normal working voltage and with a waveform similar to that of the working voltage. In this test, apply a direct voltage between neutral and ground equal to twice the working voltage of the neutral, and at the same time excite the tran