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1、BRITISH STANDARD CONFIRMED NOVEMBER 1990 BS 2950:1958 Incorporating Amendment No. 1 Specification for Cartridge fuse-links for telecommunication and light electrical apparatus UDC 621.316.923 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI B
2、S 2950:1958 This British Standard, having been approved by the Telecommunication Industry Standards Committee and endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of the General Council on 31 January 1958 BSI 11-1999 The following BSI references relat
3、e to the work on this standard: Committee references TLE4, TLE/4/1 Draft for comment CV (TLE) 7595 ISBN 0 580 02618 3 Co-operating organizations The Telecommunication Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the follow
4、ing Government departments and scientific and industrial organizations: Admiralty* British Broadcasting Corporation* British Electrical secondly, since under the conditions in which these fuse-links are intended to be used the prospective fault current is restricted, the breaking-capacity test is ma
5、de at a prospective current that does not exceed ten times the rated current of the fuse-link. The primary object of the standard is to specify cartridge fuse-links that experience has shown to be adequate for this class of service, without adding to their cost by requiring expensive proving tests.
6、Moreover, since the cost of producing fuse-links giving a close degree of protection increases with the smaller currents, and critical protection is not always required within this range, two classes of fuse-link, Grades A and B, are specified, for rated currents of 250 ma and below, which will blow
7、 at two or three times their rated currents respectively. Fuses within the scope of this standard are not sensitive to normal electromagnetic disturbances, and therefore no immunity tests are required. Significant electromagnetic disturbance generated by a fuse is limited to the instant of its opera
8、tion. Provided that the maximum arc voltages during operation in the type test comply with the requirements of the clause in this standard specifying maximum arc voltage, the requirements for electromagnetic compatibility are deemed to be satisfied. A British Standard does not purport to include all
9、 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 comprises a front cover, an inside front cover, pages i and
10、ii, pages 1 to 10, an inside back cover 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. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2
11、006, Uncontrolled Copy, (c) BSI BS 2950:1958 BSI 11-19991 Section 1. General 1 Scope This British Standard relates to non-rewirable cartridge fuse-links for use in conjunction with telecommunication or light electrical equipment where the prospective fault current of the circuit will not exceed ten
12、times the rated current of the fuse-link. Fuse-links of two grades, A and B, which will blow at two or three times their rated currents respectively, are specified for rated currents of 250 ma and below. The standard does not specify surge resisting characteristics, but for the guidance of those who
13、 wish to make tests of these characteristics, information on a suitable test is given in Appendix A. 2 Definitions For the purpose of this British Standard the following definitions apply: cartridge fuse-link a cartridge containing a fuse-element cartridge a totally-enclosing fuse-element container
14、consisting of insulating material tubular in form and having its ends enclosed by metallic caps fuse-element that part of a cartridge fuse-link which is designed to melt and thus open a circuit prospective current (of a circuit) the direct current or the r.m.s. value of the alternating current that
15、would flow in a circuit containing a cartridge fuse-link if the latter were replaced by a link of negligible impedance prospective fault current the maximum value of the prospective current that could occur under fault conditions rated current the current, stated by the manufacturer, that the cartri
16、dge fuse-link will carry in accordance with Clause 10 a) rated voltage the voltage specified in this standard is the highest voltage that may be associated with a cartridge fuse-link of a given rated current breaking capacity the capacity of a cartridge fuse-link to open an electrical circuit under
17、prescribed conditions Section 2. Requirements 3 Dimensions The dimensions of fuse-links shall be as shown in Figure 1. 4 End-caps Fuse-links shall have at each end a metallic cap with a cylindrical surface, the outer ends being substantially flat and at right angles to the axis of the cylinder. The
18、caps shall be of non-corroding metal or of metal suitably protected against corrosion and shall be effectively free from fluxes or other non-conducting substances on the contacting surfaces. The axial deviation of either end-cap to the body of the fuse-link shall be checked by means of the gauge sho
19、wn in Figure 2. The entire length of the fuse-link shall pass by its own weight through the gauge when the latter is held with its axis vertical. 5 Preferred rated currents and voltages The rated currents and voltages of the preferred range of fuse-links are specified in Table 1. A fuse-link having
20、an intermediate value of rated current shall be rated at the voltage of the fuse-link having the next higher rated current in the preferred range. 6 Minimum life Fuse-links shall be capable of passing the minimum life test specified in Clause 10 a). 7 Blowing current Fuse-links shall be capable of p
21、assing the blowing-current test specified in Clause 10 b). 8 Breaking-capacity Fuse-links shall be capable of passing the breaking-capacity test specified in Clause 10 c). Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 2 BSI 11
22、-1999 Figure 1 Dimensions of fuse-links Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 BSI 11-19993 Figure 2 Gauge for fuse-links Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy
23、, (c) BSI BS 2950:1958 4 BSI 11-1999 Table 1 Rated currents and voltages of the preferred range of cartridge fuse-links 9 Marking Each fuse-link shall be clearly and indelibly marked with the following information: a) The number of this standard, viz. BS 2950 followed by the letter A or B according
24、to the grade. b) The rated current. Fuse-links may in addition be colour-coded and, if they are, the code shall be in accordance with Table 1. Ratings which are not included in the preferred range shall not be colour coded. c) The manufacturers name or identifying mark. Rated current Amp Blowing cur
25、rent Amp See Clause 10 b) Rated voltageOptional Colour Code Grade AGrade Ba.c.d.c.Colour BS 381Ca Colour No. 0.050.100.151 0001 000Salmon Pink443 0.060.120.181 0001 000Black 0.100.200.301 0001 000Dark Admiralty Grey632 0.150.300.451 0001 000Post Office Red538 0.250.500.751 000750Dark Brown412 Grade
26、A 0.501.0750350Golden Yellow356 0.751.5500300Mid Brunswick Green226 1.02.0350250Azure Blue104 1.53.0250250Sky Blue101 24.0250250Dark violet796 36.025032White 51025032Black and White 71415032Light Orange557 102010032Light Orange and Black 557 122410032Light Orange and Dark Admiralty Grey 557 632 1530
27、5032Light Orange and Mid Brunswick Green 557 226 20403232Light Orange and Dark Violet 557 796 25503232Light Orange and White 557 NOTEThese fuse-links are not intended for use in circuits where the prospective fault current will exceed 10 times the rated current of the fuse-links. a BS 381C, Colours
28、for ready-mixed paints. These numbers are added for guidance only and are not mandatory. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 BSI 11-19995 Section 3. Tests 10 Performance tests All tests of fuse-links specified in the
29、 following clauses shall be type-tests. The fuse-links used for the type-tests shall be identical in all details likely to affect the performance with those to be used in service. Certificates of type-tests shall be deemed evidence of compliance of fuse-links with the requirements of the relevant cl
30、auses of the standard and the manufacturer shall hold available such certificates, together with detail drawings of the fuse-links and a record of any alterations that have been made in the fuse-links subsequent to the type-tests. The manufacturer shall, if required by the purchaser, certify that th
31、e fuse-links are identical in material and performance with those covered by a certificate of stated date. Type-tests may be made by the manufacturer, provided that he shall arrange for a recognized authority to make any type-tests for which he himself is not equipped. Six new fuse-link shall be use
32、d for each test. Fuse-links shall be deemed to comply with this specification only if all that are tested pass the tests. The cartridge fuse-links shall be mounted for test vertically in a metal testing enclosure as shown in Figure 3, and shall be tested at an ambient temperature of 15 25 C. Connect
33、ions shall be made with electric cable soldering tags of appropriate size to each terminal by not less than 2 ft of vulcanized rubber or P.V.C. covered cable of the following standard sizes: a) Minimum life test. Each fuse-link shall be capable of carrying its rated current for 1 000 hours. The test
34、 shall be made with not more than ten interruptions, and the current shall be held within the limits of per cent. This test may be carried out at any convenient voltage. b) Blowing-current test. The cartridge fuse-links shall blow within 10 seconds at their rated voltage and at twice their rated cur
35、rent for Grade A fuse-links, or at three times their rated current for Grade B fuse-links, immediately after having carried their rated current for not less than one minute and not more than ten minutes. The doubling or trebling of the current shall take place within one second. c) Test of breaking
36、capacity. Cartridge fuse-links of up to and including 2 amp rated current shall be tested for breaking capacity by testing each fuse-link, in the enclosure shown in Figure 3, in a d.c. circuit, at the rated voltage of the fuse-link with a tolerance of 5 per cent. Cartridge fuse-links of more than 2
37、amp rated current shall be tested in an a.c. circuit having a power factor of any convenient value between 0.8 lagging and 1.0 at the rated alternating voltage of the fuse-link, with a tolerance of 5 per cent, and also in a d.c. circuit having a time constant not exceeding 0.002 sec at the rated d.c
38、. voltage of the fuse-link with a tolerance of 5 per cent. The test circuit connections shall be as shown in Figure 4. The prospective current shall be ten times the rated current of the fuse-link. For fuse-links of up to and including 2 amp rated current six fuse-links shall be tested at their rate
39、d d.c. voltage. For fuse-links of more than 2 amp rated current six shall be tested at their rated d.c. voltage and six at their rated a.c. voltage. 11 Criteria of failure A fuse-link shall be deemed not to comply with this British Standard, if in any of the above tests one or more of the following
40、are found to have occurred: a) The fuse-link has burst violently. b) The end-caps are externally damaged. c) The fuse-link “x” has blown, indicating arcing to the metal enclosure. (See Figure 4.) Not exceeding 5 amperes3/.029 Exceeding 5 amperes but not exceeding 20 amperes 7/.029 Exceeding 20 amper
41、es7/.036 +2 0 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 6 BSI 11-1999 Figure 3 Testing enclosure Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 BSI 1
42、1-19997 Figure 4 Diagram of connections for tests Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 8 BSI 11-1999 Appendix A Recommended method for comparing the surge-resisting characteristics of small telecommunication cartridge
43、 fuse-links Figure 5 gives the circuit diagram of apparatus suitable for comparing the surge-resisting characteristics of small telecommunication cartridge fuse-links having a rated current up to and including 1 amp. The operation of the apparatus is as follows: S is a change-over switch arranged to
44、 operate at 60 second intervals and so constructed that one set of contacts opens a fraction of a second before the other closes. When Contact 1 closes, a surge of current whose peak value is controlled by the value of R and whose exponential decay is controlled by CR, flows through the fuse-link. T
45、he CR product is maintained at ten milliseconds and the values of C and R are adjusted to produce the required peak current. The time constant of ten milliseconds is chosen because it represents an average of conditions commonly occurring in practice in domestic radio and television equipment. C1, t
46、he final smoothing capacitor of the d.c. supply unit, has a value of at least ten times that of C to maintain the supply voltage sensibly constant during the current surge. After Contact 1 has opened, Contact 2 closes and discharges C ready for the next operation. The discharging surge can convenien
47、tly be used to operate a relay and counter system which of course, automatically stops when the fuse-link “blows”. It is recommended that the fuse-link should be subjected to 1 000 operations. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
48、BS 2950:1958 BSI 11-19999 Figure 5 Circuit diagram of apparatus for comparison of surge-resisting characteristics Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 10 blank Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:58:27 GMT+00
49、:00 2006, Uncontrolled Copy, (c) BSI BS 2950:1958 BSI 11-1999 British Standards The following are available on application: YEARBOOK Including subject index and numerical list of British Standards SECTIONAL LISTS. Gratis Acoustics Aircraft materials and components Building materials and components Chemical engineering Chemicals, fats, oils, scientific apparatus, etc. Cinematography and photography Coal, coke and colliery requisites Codes of Practice for buildings Consumer goods Drawing practice Electrical engineering Farming, dairying a
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