1、BRITISH STANDARD BS 5938-2: 1980 IEC 367-2: 1974 attention is especially drawn to the following. Whenever the words “recommendation” or “IECPublication367-2” appear, referring to this guide, they should bc read as “BritishStandard”. Clause1, “Scope”, andclause2, “Object”, are not presented in the ma
2、nner that is customary in British Standards. For the purposes of this British Standard the text of these clauses, excluding the notes to clause2, 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
3、 of specifications and article sheets for magnetic cores made of magnetic oxides or metallic powders and used in inductors and transformers for telecommunication equipment and electronic devices employing similar techniques. The subject of the specifications is the detailing of core properties which
4、 may be of importance in the most common applications of these cores. At present there are no corresponding British Standards for the following IECPublications referred to in the text: IEC133:1967, IEC205:1966 and IEC401:1972. The technical committee has reviewed the provisions of these IEC Publicat
5、ions and has decided that they are acceptable for use in conjunction with this standard. “I.E.V.”, referred to in the text, is “International Electrotechnical Vocabulary” published by IEC. The related British Standard is BS4727, of which Part1:Group07 is particularly relevant. A British Standard doe
6、s not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British S
7、tandard IEC 367-1:1971 BS5938 Cores for inductors and transformers for telecommunications Part 1:1980 Methods of measurement (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1to14, an inside back cover and a back cover. This standard has b
8、een updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5938-2:1980 BSI 12-1999 1 1 Scope This recommendation applies mainly to magnetic cores made of magnetic oxides or metallic powders used in inductors an
9、d transformers for telecommunication equipment and electronic devices employing similar techniques. 2 Object of Part2 To give guidance on the drafting of specifications and article sheets for magnetic cores, the subject of the specifications being the core properties which may be of importance in th
10、e most common applications of these cores. NOTE 1Data on any, or all, of the characteristics listed in the specialized clauses may be required. NOTE 2Since the values measured for certain characteristics depend upon the geometry and position of the measuring coil, this coil shall be specified in suf
11、ficient detail before agreement can be reached on the value of such characteristics. NOTE 3Where limits for core losses measured with a coil are stated in a specification, the coil losses shall be made negligible or a correction applied. NOTE 4Equations are given for basic SI units only. In specific
12、ations and article sheets, the following multiples or sub-multiples will normally be used: NOTE 5The following standard symbols are used in the formulae of this recommendation: 3 General information 3.1 References For the definitions of the terms used in this guide see: 3.2 General explanation on me
13、asuring and testing 3.2.1 Direct measuring methods The direct measuring methods allow the measurement of the characteristics of the cores directly and should therefore be used when comparing different cores made of different materials by different manufacturers such as is done in the case of type te
14、sts. For these test methods, reference should be made to Part1. mm 1 for core factor C 1 , mm 3 for core factor C 2 , kHz for frequency, mH for inductance, nH for inductance factor, mT for flux density, mA for current, kA/m for magnetic field strength. t = time, = temperature, L = self-inductance, o
15、 = magnetic constant,0.4; 10 6 H/m, r = relative permeability, a i = initial permeability, e = effective permeability = rev = reversible permeability, N = number of turns on the measuring coil, C 1and C 2= core factors defined in IECPublication205, Calculation of the Effective Parameters of Magnetic
16、 Piece Parts, A e = effective cross-sectional area, = angular frequency=2; frequency of measuring current. a In the case of qualified versions of permeability, such as initial permeability i , the relative quantity is meant, unless otherwise stated. IEC Publication 50: International Electrotechnical
17、 Vocabulary; Advance Edition ofI.E.V:Chapter901: Magnetism. For the effective parameters (core factors and effective dimensions), see: IEC Publication 205: Calculation of the Effective Parameters of Magnetic Piece Parts. LC 1 o N 2 -BS5938-2:1980 2 BSI 12-1999 3.2.2 Indirect measuring methods The in
18、direct measuring methods only allow the comparison of cores of the same construction and material, made by the same manufacturer. Their use is therefore restricted to those cases where the correlation with the direct measuring methods has been established. After agreement between manufacturer and pu
19、rchaser (or his nominee), they may be used for factory tests and for acceptance tests. 3.2.3 Type of core A type comprises cores having definite common features and manufactured by the same technology. NOTECommon features cover in general the core shape and the properties of the material used. 3.2.4
20、 Test A procedure followed in order to determine whether a particular requirement of a specification is met. 3.2.5 Type test A series of tests carried out on a number of specimens representative of the type with the object of determining whether a particular manufacturer is able to make products mee
21、ting the specification. 3.2.6 Type approval (qualification approval) Decision by the appropriate authority that a particular manufacturer is able to produce, in reasonable quantity, a product meeting the specification. 3.2.7 Quality conformance tests Tests carried out under the responsibility of the
22、 manufacturer to ensure that products accepted for delivery comply with the specification. 3.2.8 Number of specimens 1) General The number of specimens to be tested in any particular case depends upon the purpose of the testing and the accuracy to be achieved for the result. 2) Type testing In the c
23、ase of type tests, the sample shall be representative of the range of values (sizes, A Lvalues, tolerances, etc.) of the type under consideration. The appropriate number of specimens to be tested shall be agreed upon between customer and supplier. NOTEPart of a full range, or individual values, may
24、be subjected to type tests in order to gain limited type approval. 3) Failures This guide does not specify the number of permissible failures; this is considered to be the prerogative of the authority giving type approval. 3.3 Sub-division of the characteristics Recommendations for the characteristi
25、cs to be specified for the various types of cores are listed in Clauses4 and onwards. They depend upon the general application of the core. These lists of characteristics are divided into two parts serving the following main purposes: to state the minimum information on performance characteristics r
26、equired in specifications for transformer and inductor cores, referred to as “minimum information in core specifications”. to give recommendations for further information which may be supplied by the manufacturer for the use of designers, referred to as “additional information on cores”. In addition
27、 to these two categories, guidance on mechanical requirements may be given. 3.4 Definitions of terms In addition to those included in IECPublication50(901), Advance edition of International Electrotechnical Vocabulary(I.E.V.), Chapter901: Magnetism, the following definitions apply for the purpose of
28、 this publication.BS5938-2:1980 BSI 12-1999 3 3.4.1 Apparent permeability app The inductance, L, of a measuring coil when assembled in a specified position on a given core, divided by the inductance, L, of the same coil measured without the core: 3.4.2 Toroidal permeability tor NOTEThis term is depr
29、ecated on the ground that it does not refer to a magnetic property but rather to a method of measurement. The relative permeability of a material, measured on a toroid of the material: L = inductance of the coil ofN turns on the core L = inductance of the same coil without core 3.4.3 Turns factor !
30、NOTEThe use of this term is deprecated because this quantity is not compatible with S.I. units. The number of turns that a coil of specified geometry, placed on a given core in a specified position, should have to obtain unit inductance: N = number of turns on the specified measuring coil L = induct
31、ance of the measuring coil when placed on the core NOTEIf the unit of inductance is a submultiple of the henry (normally the millihenry), this shall be stated. 3.4.4 Inductance factor A L The inductance of a coil of specified geometry, placed on a given core in a specified position, divided by the s
32、quare of the number of turns: N = number of turns on the specified measuring coil L = inductance of the measuring coil when placed on the core NOTE 1This term is closely related to permeance(A)(I.E.V.901-01-16); the latter refers to the reluctance of a core while inductance factor refers to the core
33、 with a winding. NOTE 2In principle A Lcan apply to the several forms of permeability defined in theI.E.V.,e.g. amplitude permeability but, unless otherwise specified, it should be assumed that it corresponds to the initial effective permeability. 3.4.5 Hysteresis core constant i An expression of th
34、e hysteresis loss of a magnetic core operating in the Rayleigh region. It is equal to the tangent of the loss angle due to hysteresis divided by the product of the peak currentand the square root of the inductance(L) of the measuring coil: NOTEThe relation between the hysteresis material constant an
35、d the hysteresis core constant is: ) B= hysteresis material constant (seeI.E.V.901-03-20) V e= effective volume (seeIECPublication205, Calculation of the Effective Parameters of Magnetic Piece Parts) ( i )BS5938-2:1980 4 BSI 12-1999 3.4.6 Variability The changes in the magnetic properties of a mater
36、ial or magnetic circuit with time or with operating conditions, or both. NOTENormally variability refers more specifically to changes of permeability. Temperature dependence of permeability and disaccommodation are the most common examples of variability. 3.4.7 Temperature factor ! F The negative of
37、 the change in the reluctivity (reciprocal of permeability) of a material due to change in temperature divided by that change in temperature: where F ref is the effective permeability at temperature ref . 3.4.8 Temperature coefficient of permeability ! 4effective permeability ! 4e inductance ! L The
38、 fractional change of permeability effective permeability inductance due to a change of temperature divided by that change in temperature: where L 0L ref is the inductance at temperature ref andF ref is the effective permeability at temperature ref . 3.4.9 Disaccommodation D The fractional decrease
39、of permeability of a magnetic material measured at constant temperature over a given period of time: where 1and 2are successively measured values of relative permeability at the beginning and the end of the given period. 3.4.10 Disaccommodation coefficient d The disaccommodation after magnetic condi
40、tioning divided by the logarithm (to the base of10) of the ratio of the time intervals between the cessation of that conditioning and the second and first measurement respectively: where, in this context, D is the disaccommodation measured over the period of time betweent 1andt 2after magnetic condi
41、tioning. 3.4.11 Disaccommodation factor D F A quantity obtained by dividing the disaccommodation coefficient by the relative permeability measured at the first measuring time: 3.4.12 Magnetic conditioning A treatment of a magnetic material or core to obliterate its magnetic history and to put it in a well-defined and reproducible magnetic state.
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