1、0 British Standards Institution. No part of this publication may be photocopied or otherwise reproduced without the prior permission in writing of BSI British Standard Cores for inductors and transformers for telecommunications Part 1. Methods of measurement Noyaux pour bobines dinductance et transf
2、ormateurs destins aux tlcommunications Partie 1. Mthodes de mesure Kerne fr Induktoren und Transformatoren der Fernmeldtechnik Teil I. Messverfahren British Standards Institution Y BSI BS*5938: PART*i(L 84 EM 1b24bb9 0087304 b U BS 5938 : Part.1 : 1984 National foreword This Part of this British Sta
3、ndard has been prepared under the direction of the Electronic Components Standards Committee, It is identical with the second edition of IEC Publication 367-1 Cores for inductors and transformers for telecommunications Part 1 Measuring methods, published in 1982 by the International Electrotechnical
4、 Commission (IEC). The international text embodies IEC 367-1 of 1971, and its supplements 1A to 1F inclusive, which were incorporated in the first edition of the British Standard, together with the new measuring methods ofclause 16 Magnetic properties under pulse conditions, and clause 17 (Effective
5、) Amplitude permeability. BS 5938 : Part 1 : 1980 is withdrawn. Terminology and conventions. The text of the international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in Bri
6、tish Standards; attention is drawn especially to the following. Wherever page numbers are quoted, they are IEC page numbers. Clause 1, Scope and clause 2, Object are not presented in a manner that is customary in British Standards. For the purposes of this British Standard, the text of clause 1, tog
7、ether with paragraph 1 of clause 2, should be read as the following, which makes no change in the technical meaning. Scope This Part of this British Standard gives guidance on the drafting of those parts of specifications for magnetic cores that are concerned with measuring methods for magnetic and
8、electric core properties. The cores covered by this standard are made primarily of magnetic oxides or metallic powders and used in inductors and transformers for telecommunication equipment and electronic devices employing similar techniques. This standard is limited to the general principles to be
9、followed for various possible test methods, and it sets out the factors to be taken into account when deciding on the description of the test method to be included in the specification. Cross-references International standards Corresponding British Standards IEC 51 : 1973 BS 89 : 1977 Specification
10、for direct acting electrical measuring instruments and their accessories (Identical) BS 201 1 Basic environmental testing procedures Part 2.1A : 1977 Tests A. Cold (Identical) Part 2.1B : 1977 Tests B. Dry heat (Identical) BS 6454 : 1983 Method for calculation of the effective parameters of magnetic
11、 piece parts (Identical) IEC 68 IEC68-2-1 : 1974 IEC 68-2-2 : 1974 IEC205 : 1966 The Technical Committee has reviewed the provisions of IEC 317-2 : 1970, to which reference is made in the text, and. has decided that they are acceptable for use in conjunction with this standard. The related British S
12、tandard for IEC 317-2 : 1970 is BS 4738 : Part 1 : 1971. Compliance with a British Standard does not of itself confer immunity from legal obligations. CONTENTS National foreword . Inside front cover Committees responsible . Back cover Page Clause SECTION ONE - GENERAL 1. Scope 3 2. Object 3 4. Gener
13、al precautions for methods involving permeability measurements . 4 4 3. Environmental conditions L 5 5. 6 6. Magneticconditioning 7 7. Inductance measurement General precautions for loss measurement at low flux density SECTION TWO - COMMON MEASURING METHODS 8. Disaccommodation . 8 9. Variation of pe
14、rmeability with temperature 10 10, Range of inductance adjustment . 13 11. Losses 15 SECTION THREE - SPECIALIZED MEASURING METHODS 12. Thirdharmonicdistortion 21 13. Magnetic shock sensitivity 23 Contribution of the adjusting device to the core instability 15. Influence of a staticmagnetic field 28
15、16. Magnetic properties under pulse conditions . 29 17. (Effective) Amplitude permeability . 37 14. 25 APPENDICES A -Apparatus for magneticconditioning with capacitor discharge . 40 B -Poweramplifierformagneticconditioning . 42 C -Apparatus for magnetic conditioning based on the alternating field me
16、thod D -Thermal method for magnetic conditioning . 45 44 E - Guide for the design of inductance measuring coils for newly developed types of cores 46 1 BSI BS*5938: PART*L BY LbZYbb 0087306 T R BS 5938 : Part 1 : 1984 APPENDICES F - Methods of expressing temperature dependence G - Damped oscillation
17、 method for loss measurement calibration H - Transmission method for loss measurement calibration . J - Examples of circuits for measuring total core loss K - Example of a circuit for measuring third harmonic distortion (low impedance method) L - Methods of inductance measurement in the presence of
18、a static magnetic field . M- Examples of circuits for pulse measurements N - Examples of circuits for measuring (effective) amplitude permeability . 2 BSI BS*5938: PART*1 84 W 1624669 0087307 1 I BS 5938 : Part 1 : 1984 British Standard Cores for inductors and transformers for telecommunications Par
19、t I. Methods of measurement 1. Scope This standard applies to magneticcores, mainly made of magnetic oxides or metallic powders, used in inductors and transformers for telecommunication equipment and electronic devices employing similar techniques. Some of the methods described in this standard may
20、also be suitable for magnetic cores used in other components. 2. Object To give guidance for the drafting of those parts of specifications for magnetic cores that are con- cerned with measuring methods for magnetic and electric core properties. This standard is limited to the general principles to b
21、e followed for various possible test methods and it sets out the factors to be taken into account when deciding on the description of the test method to be included in the specifica- tion. In accordance with the use made of the measuring methods, this Part 1 has been sub-divided into three sections
22、as follows: - Section One: General, including general stipulations and methods generally used in combination with measuring methods included in Sections Two and Three; parts of inductor and transformer core measurements; poses and used only in special cases for specification purposes. - Section Two:
23、 Common measuring methods, including those methods which are used for important - Section Three : Specialized measuring methods, including methods intended for information pur- Note. - AU formulae in this standard use basic SI unifs. When multiples or submultiples are used, the appropriate power of
24、10 shaU be introduced. The foliowing standard symbols are used in these formulae: f = time e = temperature L = self inductance Po Pr = relative permeability* i4 = initial permeability Pe ? Cl and C, = core factors defined in IEC Publication 205: Calculation of the Effective Parameters of Magnetic =
25、magnetic constant, 0.4 x X lod H/m = effective permeability = LCl/hfl = reversible permeability = number of turns of measuring coil Piece Parts = effective cross-sectional area = .angular frequency = 2 n X frequency of measuring current 4- w *In the case of qualified versions of permeability, such a
26、s initial permeability fi, the relative quantity is meant, unless otherwise stated. 3 IEC page 151 ES1 BS*593: PART*l 84 H Lb24bb9 i3887308 3 e BS 5938 : Part 1 : 1984 3. Environmental conditions 3.1 General Normally,.the cores are magnetically conditioned in accordance with Clause 6, not less than
27、24 h During the whole proeedure, the core shall be protected against mechanical shock and vibration and against magnetic disturbances. Condensation on measuring windings, which may occur at changing temperature, should be avoided. before the measurements start. 3.2 Ambient temperature Unless otherwi
28、se specified, the whole measurement procedure shail take place at a temperature within the range of standard atmospheric conditions for testing according to IEC Publication 68: Basic Environmental Testing Procedures. During the whole period of the measurement, however, the tem- perature shall not va
29、ry to such an extent as to have an appreciable effect on its results. In some cases, this may necessitate the use of a temperature controlled chamber. sufficient time to reach thermal equilibrium. The temperature during measurement shail be stated. The assembled cores with measuring coil and clampin
30、g devices shail be kept in this environment for a Note. -This clause means that the measurements may be made at any temperature within the range of 15C to 35C but that, if the specified limits are exceeded, it is allowed to repeat the measurements, preferably at 25 k 1C or at one of the other standa
31、rd temperatures for referee tests: 2O+l0C, 23 f l0C, or 27 k 1C). 4. Generai precautions for methods involving permeability measurements 4.1 Parameters involved The effective permeabiiity of a core depends upon many factors, among which are the magnetic history, time, temperature, field strength, me
32、chanical pressure, frequency of measuring current, core geometry and geometry and position of the measuring coil. Various methods described in this standard single out one of these factors at a time, e.g. time or temperature, and the precautions during these measurements should be directed towards e
33、liminating the influence of all other factors. For example, a clamping device should be such that the pressure remains constant in time and with temperature, so that the measuring result is not influenced by changing pressure. 4.2 Relation to practice The measuring conditions shall be so chosen that
34、 the measured results are suitable for predicting the performance of the core under practical circumstances. This does not imply that all conditions have to correspond to those prevailing in practice. 4.3 Mounting of cores consltng of more than one part clamping device shall be used throughout the m
35、easrements. This clamping device shail be able to: For cores consisting of more than one part and which are assembled around the measuring coil, a - distribute the clamping force uniformly over the contact surfaces, without introducing bending stresses in the core; - hold the core parts rigidly in p
36、osition relative to each other; - give a transient overforce of about 10% when being closed, in order to break down fine irregularities between the cleaned contact surfaces; 7 4 BSI BS*5938: PART*ieL BL1 Is I1624669 0087309 5 W BS 5938 : Part 1 : 1984 - exert a specified clamping force +5%; - keep t
37、he force constant within fl% during the total period of the measurement. Note. - Keeping the force within fl% is considered sufficient when the specified clamping force is chosen in the flat portion of the curve of permeability versus force. Otherwise closer tolerances may be required. The mounting
38、of such cores shall be done in accordance with the following instructions: The contact surfaces shall be inspected for damage and cleanliness. Damaged cores shall not be used. When necessary, the contact surfaces shall be cleaned by non-abrasive means, e.g. by rubbing gently on a dry wash-leather. D
39、ust particles shall be blown off with clean dry compressed gas. The contact surfaces shall never be touched with the bare fingers. The core parts shall then be assembled around the measuring coil, the latter being locked in position with respect to the core by suitable means, e.g. a foam washer. The
40、 core parts are cenfred and the core placed in the clamping device. The clamping force specified in the relevant specification shall then be applied. The clamped cores shall be kept under the specified environmental conditions (see Clause 3) for a time sufficient to allow any variation of effective
41、perme- ability with time due to clamping to become negligible. 5. General precautions for loss measurement at low flux densify 5.1 Contributory losses At low flux density (Le. within the Rayleigh region), the loss measured on a core by means of a coil or other coupling device is due to a number of c
42、auses; some may be inherent in the core itself, some in the coupling device and some in the connection between the coupling device and the measuring instrument, For measurements with coils, the foilowing contributory losses can be distinguished: core loss; d.c. coil loss; losses due to skin effect a
43、nd proximity effect; dielectric loss in the coil; loss in connecting wires and loss in any associated component (e.g. resonating capacitor). An attempt should be made to isolate the core loss from the total loss measured, either by correction or by choosing the conditions so as to make the other con
44、tributory losses negligible. The d.c. coil loss and the loss in any associated component can be measured separately; the other contributory losses may be either calculated or determined experimentally. The determination of fhe core loss does not present undue difficulties for ferrite cores without a
45、n air- gap or with a very small air-gap (e.g. toroids and pot cores without intentional air-gap) because, with a suitably designed coil, the core loss then is appreciably higher than any other of the contributory losses. This may not be the case for loss measurement on gapped cores for which it may
46、be difficult to obtain a sufficiently accurate result for the core Ioss alone. Two methods may then be followed: 1) Measure the loss factor before the air-gap is ground and calculate the loss in the gapped core. Note. - It is not permissible to measure the loss factor on an ungapped core having a ge
47、ometry different from that of the gapped core, for example, on a toroid of the same material, since the eddy current core loss strongly depends upon the core geometry. 5 IEC page 191 ,BSI BS*5938: PART*3 84 1624669 0087330 1 E BS 5938 : Part 1 : 1984 2) Make no attempt to separate core and coil loss
48、 but compare the combined loss of the core and the measuring coil with the results obtained from similar measurements of other cores using a coil of identical construction and having the same d.c. resistance. The best policy is to obtain these measuring coils from the same source and from time to ti
49、me compare the results of measurements with various coils on the same cores. Furthermore, the measuring results should be accompanied by the d.c. resistance value of the coil; when comparing the results obtained with different coils, the measurements shall be corrected to allow for the difference in coil resistance, 5.2 Mounting Coupling between the stray field of the core and extraneous objects shall be avoided. Connections between the measuring coil or other coupling device and the measuring instrument shall be short, direct and so fixed that movement of the spe
