1、BRITISH STANDARD BS 5772-3: 1979 IEC 512-3: 1976 Specification for Electromechanical components for electronic equipment: basic testing procedures and measuring methods Part 3: Current-carrying capacity tests UDC 621.316.54.001.4:621.3.014.36:536.5BS5772-3:1979 This British Standard, having been pre
2、pared under the directionof the Electronic Components Standards Committee, was published underthe authority of the Executive Board and comes into effect on 30 November 1979 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference ECL/21 Draft for comment 78/2
3、7024 DC ISBN 0 580 11058 3 Cooperating organizations The Electronic Components Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government department and scientific and industrial organizations: British Electrical and Allie
4、d Manufacturers Association (BEAMA) Electricity Supply Industry in England and Wales* Electronic Components Industry Federation* Electronic Engineering Association Institution of Electronic and Radio Engineers Ministry of Defence* National Supervising Inspectorate* Post Office* Society of British Ae
5、rospace Companies Limited* Telecommunication Engineering and Manufacturing Association (TEMA) The organizations marked with an asterisk in the above list were directly represented on the committee entrusted with the preparation of this British Standard. Amendments issued since publication Amd. No. D
6、ate of issue CommentsBS5772-3:1979 BSI 10-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii Scope 1 1 Test 5a: Temperature rise 1 2 Test 5b: Current-temperature derating 1 Figure 1 Example of a current-carrying capacity curve 3 Figure 2 Example of a derating curv
7、e 3 Figure 3 Measuring apparatus arrangement 3BS5772-3:1979 ii BSI 10-1999 National foreword This Part of this British Standard, published under the direction of the Electronic Components Standards Committee, is identical with IEC Publication512-3 “Electromechanical components for electronic equipme
8、nt; basic testing procedures and measuring methods Part 3: Current-carrying capacity tests” published by the International Electrotechnical Commission (IEC). This Part should be read in conjunction with Part 1 “General” of BS5772 (IEC Publication512) which contains information on fundamental test me
9、thods and procedures to be employed in implementing the requirements of this standard. Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a British Standard. Some terminology and certain conventions are not identic
10、al with those used in British Standards; attention is especially drawn to the following. In Figure 2 a comma has been used as the decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. NOTE 1Textual error. When adopting the text of the
11、International Standard, the printing error given below was noticed. In2.3.1 the symbol for thermal conductivity “W/(m K)” was misprinted as “W/mK”. Additional information. The scope of this British Standard is as given in BS5772-1:1979. Part 3 of this standard prescribes the current-carrying capacit
12、y tests. A British Standard does 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. Summary of pages This document c
13、omprises a front cover, an inside front cover, pages i and ii, pages 1 to 4 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5772-3:1979 BSI 10-1999 1 Scope The te
14、sts contained herein, when required by the detail specification, shall be used for electromechanical components within the scope of Technical Committee No. 48. 1) They may also be used for similar devices when specified in a detail specification. 1 Test 5a: Temperature rise 1.1 Object The object of
15、this test is to detail a standard test method to assess the ability of a component to carry continuously its specified current without exceeding a specified temperature rise. 1.2 Preparation of the specimen The specimen shall be fitted with temperature-sensing device(s), wired with a minimum length
16、of500mm (20in) of the specified size wire, and mounted as specified in the detail specification. NOTECare must be taken to protect the specimen under test from draughts or other artificial cooling. 1.3 Test method A specified test current shall be applied to each contact of the specimen for a period
17、 of5h. Ambient temperature shall be recorded before and after the test. 1.4 Requirements a) Every contact of the specimen must be capable of carrying the specified test current for a period of5h without exceeding the specified temperature rise. 1.5 Details to be specified When this test is required
18、by the detail specification, the following details shall be specified: a) location and sensitivity of temperature-sensing device(s); b) wire size; c) wiring of specimen and type of termination; d) mounting of specimen; e) a.c. or d.c. current; f) temperature rise, preferred values are20 C,30 C and40
19、 C; g) ambient temperature; h) any deviation from standard test method. 2 Test 5b: Current-temperature derating 2.1 Object The object of this test is to detail a standard test method to assess the current-carrying capacity of electromechanical components. 2.2 General conditions 2.2.1 Determining the
20、 current-carrying capacity curve The current-carrying capacity is limited by the thermal properties of the materials which are used for the contacts and terminals as well as by the insulating materials. Therefore, it is a function of the self-generated heat and the ambient temperature within which a
21、 device is operating. Using the measuring method given in Sub-clause2.4, the temperature of a measuring point t b(approximately the hottest spot) of the component and the temperature in the immediate environment t uof the component are measured at various currents. The difference between the two tem
22、peratures is the self-heating or rise created by the current flow. This may be expressed as: The relation between the current, the temperature rise and the ambient temperature of the component is represented by a curve as shown in Figure 1, page3. Unless otherwise specified, the temperature rise is
23、based upon the mean current of three specimens. The mean value derived from the measured values of these three specimens serves as the basic curve. At least three points of the basic curve shall be established. The permissible upper-limit temperature of the materials employed is plotted as a vertica
24、l line on the graphs shown in Figure 1 and Figure 2, page 3, with current I as the ordinate and the temperaturet as the abscissa. The temperature rise %t (mean value of three specimens), determined at current I n , is deducted. From this, the maximum permissible ambient temperature t ufor the load c
25、urrent I nis obtained, since the sum of the ambient temperature t uand the temperature rise %t must not exceed the upper temperature limit of the materials. 1) Scope of Technical Committee No. 48: To prepare International Standards regarding components having an inherent electromechanical connecting
26、 or switching function, intended for use in equipment for telecommunication and in electronic devices employing similar techniques. NOTE 1R.F. connectors will not be dealt with by this Technical Committee as they will be covered by Technical Committee No. 46 together with r.f. cables. NOTE 2Sockets
27、for components such as crystals or electronic tubes shall be considered in co-operation with the relevant Technical Committee. t b t u= %tBS5772-3:1979 2 BSI 10-1999 2.2.2 Derating curve A derating curve, derived from the basic curve (seeFigure 2, page 3) determined in accordance with Sub-clause 2.2
28、.1, shall be specified in the relevant detail specification. This curve takes into account variations in specimens as well as errors in temperature measurements in the measuring equipment. The derating factor is justified because the current-carrying capacity may be limited further by external facto
29、rs, e.g.the size of the wire and unequal distribution of the loaded circuits. If these factors result in a current-carrying capacity other than that which may be expected due to thermal limitations, then a revised value shall apply. NOTEIn practice, it is usually the case that all terminals are not
30、loaded simultaneously with the maximum permissible current. In many cases, the individual terminals can carry several times the derated current indicated by the derating curve when less than20% of the total complement is used. For these cases, general rules cannot be established and the limits must
31、be determined for the individual case. It is recommended that the method described in this standard be used accordingly in these cases. 2.2.3 Application of the current-carrying capacity curve The derating curve determined in accordance with Sub-clause 2.2.2 represents the official current-carrying
32、capacity curve as defined by this standard. Since it gives the maximum permissible current as a function of the ambient temperature, it is truly a derating curve. The cross-hatched area shown in Figure 2 indicates the permissible operating range. NOTEIf the detail specification specifies current-car
33、rying capacity data, then the current-carrying capacity curve given in this standard shall be cited. If values in tabular form are preferred, they should coincide with the current-carrying capacity curve. 2.3 Details of the test 2.3.1 Measuring apparatus The measurement shall be carried out in air a
34、s undisturbed as possible. Therefore, the specimen must be mounted in an enclosure which protects the immediate environment from external movements of air. The enclosure should be made of a non-reflective material. The sides of the enclosure may be movable to accommodate different specimen sizes. Th
35、e sides shall not be closer than20cm (8in) from the edges of the specimen. The enclosure is not required to have a lid. The specimen is arranged in the enclosure in a horizontal attitude5cm (2in) above the bottom of the enclosure and at least15cm (6in) below the top and equidistant from the sides. A
36、s nearly as possible, the specimen shall be in free suspension. If this is not possible, a thermal insulating material with a thermal conductivity of u 2 W/mK may be used provided that not more than20% of the surface of the specimen is in contact with the insulating material. The specimen shall be c
37、onnected with wires of suitable cross-section for the maximum current to be expected or according to the size of the termination. In order to reduce external heat dissipation to a minimum, at least25cm (10in) of the connecting wires shall be within the measuring enclosure. In the case of multipole s
38、pecimens, all contacts shall be wired in series with wire the same size as the connecting wires. These links shall be25cm (10in) in length. NOTE 1In the case of specimens with moving contacts, care shall be taken that the contacts are not disturbed by the connecting wires. NOTE 2A mated connector se
39、t is considered a single specimen. NOTE 3When the specimen is a free connector with a cable attached, at least25cm (10in) of the cable shall be contained within the measuring enclosure. The series connection of the contacts shall be made through the attached cables at a distance of25cm (10in) from t
40、he specimen. 2.3.2 Details of temperature measurement The temperature is measured with two temperature probes. The probe leads pass through the insulation walls of the measuring apparatus. The measuring point for measuring the ambient temperature shall be located in a horizontal plane passing throug
41、h the axis of the specimen. It shall be located5cm (2in) from the mid-point of the edge of the longest side of the specimen. The measuring point for measuring the temperature of the specimen shall be as stated in the detail specification. NOTEThe temperature probes could be thin thermocouples, e.g.n
42、ichrome/nickel wire with a diameter u 0.3mm (0.012in). If thermocouples with the same type of calibration curve are used for both temperature probes, they may be connected in opposition in the measuring circuit. In this case, the temperature rise %t is measured directly (see Figure 3, page 3). Howev
43、er, t bshould be monitored to ensure that it does not exceed the upper temperature limit of the materials.BS5772-3:1979 BSI 10-1999 3 Figure 1 Example of a current-carrying capacity curve Figure 2 Example of a derating curve Figure 3 Measuring apparatus arrangementBS5772-3:1979 4 BSI 10-1999 2.4 Met
44、hod of measurement The specimen is arranged in the measuring enclosure as described in Sub-clause 2.3.1 and its terminals are connected to a regulated power supply through an ammeter. The loading current may be a.c. or d.c. When a.c. current is used, the r.m.s. value applies. The current shall be ma
45、intained for a period not to exceed1h, or until thermal stability is achieved, at each of the selected current levels. 2.5 Details to be specified When this test is required by the detail specification, the following details shall be specified: a) preparation of the specimen: b) type and size of cab
46、le/wire bundle to be used; c) measuring point for specimen temperature; d) upper temperature limit; e) number of specimens, if other than three, and f) any deviation from the standard test method.blankBS 5772-3: 1979 IEC 512-3: 1976 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitu
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