1、BRITISH STANDARD CONFIRMED NOVEMBER1990 BS2950:1958 Incorporating Amendment No.1 Specification for Cartridge fuse-links for telecommunication and light electrical apparatus UDC 621.316.923BS2950:1958 This British Standard, having been approved by the Telecommunication IndustryStandards Committeeand
2、endorsed bytheChairman of the Engineering Divisional Council,was published undertheauthority of the GeneralCouncil on 31January1958 BSI11-1999 The following BSI references relate to the work on this standard: Committee references TLE4,TLE/4/1 Draft for comment CV (TLE)7595 ISBN 0 580 02618 3 Co-oper
3、ating organizations The Telecommunication Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Admiralty* British Broadcasting Corporation* British
4、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 made at a prospective current that does not exceed ten times the rated current of the fuse-link. The primary object of the stan
5、dard 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. Moreover, since the cost of producing fuse-links giving a close degree of protection increases with the smaller currents, and
6、 critical protection is not always required within this range, two classes of fuse-link, Grades A and B, are specified, for rated currents of250ma and below, which will blow at two or three times their rated currents respectively. Fuses within the scope of this standard are not sensitive to normal e
7、lectromagnetic disturbances, and therefore no immunity tests are required. Significant electromagnetic disturbance generated by a fuse is limited to the instant of its operation. Provided that the maximum arc voltages during operation in the type test comply with the requirements of the clause in th
8、is standard specifying maximum arc voltage, the requirements for electromagnetic compatibility are deemed to be satisfied. 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 w
9、ith 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, pagesi andii, pages1 to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amen
10、dments incorporated. This will be indicated in the amendment table on the inside front cover.BS2950:1958 BSI 11-1999 1 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
11、prospective fault current of the circuit will not exceed ten 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 of250ma and below. The standard does not specify surge r
12、esisting characteristics, but for the guidance of those who 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-el
13、ement cartridge a totally-enclosing fuse-element container 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 c
14、urrent or the r.m.s. value of the alternating current that 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 curre
15、nt the current, stated by the manufacturer, that the cartridge fuse-link will carry in accordance with Clause10 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
16、a cartridge fuse-link to open an electrical circuit under 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
17、flat and at right angles to the axis of the cylinder. The 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 o
18、f the fuse-link shall be checked by means of the gauge shown 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 o
19、f fuse-links are specified in Table 1. A fuse-link having 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
20、10 a). 7 Blowing current Fuse-links shall be capable of passing the blowing-current test specified in Clause10 b). 8 Breaking-capacity Fuse-links shall be capable of passing the breaking-capacity test specified in Clause10 c).BS2950:1958 2 BSI 11-1999 Figure 1 Dimensions of fuse-linksBS2950:1958 BSI
21、 11-1999 3 Figure 2 Gauge for fuse-linksBS2950:1958 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.BS2950 followed by t
22、he letter A or B according 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. Ra
23、ted current Amp Blowing current Amp SeeClause10 b) Rated voltage Optional Colour Code Grade A Grade B a.c. d.c. Colour BS381C aColour No. 0.05 0.10 0.15 1000 1000 Salmon Pink 443 0.06 0.12 0.18 1000 1000 Black 0.10 0.20 0.30 1000 1000 Dark Admiralty Grey 632 0.15 0.30 0.45 1000 1000 Post Office Red
24、538 0.25 0.50 0.75 1000 750 Dark Brown 412 Grade A 0.50 1.0 750 350 Golden Yellow 356 0.75 1.5 500 300 Mid Brunswick Green 226 1.0 2.0 350 250 Azure Blue 104 1.5 3.0 250 250 Sky Blue 101 2 4.0 250 250 Dark violet 796 3 6.0 250 32 White 5 10 250 32 Black and White 7 14 150 32 Light Orange 557 10 20 1
25、00 32 Light Orange and Black 557 12 24 100 32 Light Orange and Dark Admiralty Grey 557 632 15 30 50 32 Light Orange and Mid Brunswick Green 557 226 20 40 32 32 Light Orange and Dark Violet 557 796 25 50 32 32 Light Orange and White 557 NOTEThese fuse-links are not intended for use in circuits where
26、the prospective fault current will exceed10times the rated current of the fuse-links. a BS381C, Colours for ready-mixed paints. These numbers are added for guidance only and are not mandatory.BS2950:1958 BSI 11-1999 5 Section 3. Tests 10 Performance tests All tests of fuse-links specified in the fol
27、lowing 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 clause
28、s 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 the fu
29、se-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 used fo
30、r 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 of1525 C. Connections s
31、hall be made with electric cable soldering tags of appropriate size to each terminal by not less than2ft 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 for1000hours. The test shall be m
32、ade 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 within10seconds at their rated voltage and at twice their rated current for Grad
33、eA 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 capacity. Cart
34、ridge fuse-links of up to and including2amp 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 of5percent. Cartridge fuse-links of more than2amp rated current sha
35、ll be tested in an a.c. circuit having a power factor of any convenient value between0.8 lagging and1.0 at the rated alternating voltage of the fuse-link, with a tolerance of5per cent, and also in a d.c. circuit having a time constant not exceeding0.002sec at the rated d.c. voltage of the fuse-link
36、with a tolerance of 5per 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 including2amp rated current six fuse-links shall be tested at their rated d.c. voltage. For fuse-links
37、 of more than2amp 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 are found to have occurred: a) T
38、he 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 exceeding5amperes 3/.029 Exceeding5amperes but not exceeding20amperes 7/.029 Exceeding20amperes 7/.036 +2 0BS2950:1958 6 BSI 11-1999
39、 Figure 3 Testing enclosureBS2950:1958 BSI 11-1999 7 Figure 4 Diagram of connections for testsBS2950:1958 8 BSI 11-1999 Appendix A Recommended method for comparing the surge-resisting characteristics of small telecommunication cartridge fuse-links Figure 5 gives the circuit diagram of apparatus suit
40、able for comparing the surge-resisting characteristics of small telecommunication cartridge fuse-links having a rated current up to and including1amp. The operation of the apparatus is as follows: S is a change-over switch arranged to operate at60second intervals and so constructed that one set of c
41、ontacts opens a fraction of a second before the other closes. When Contact1 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. The CR product is maintained at ten milliseconds and the values of C a
42、nd 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. C 1 , the final smoothing capacitor of the d.c. supply unit, has a value o
43、f at least ten times that of C to maintain the supply voltage sensibly constant during the current surge. After Contact1 has opened, Contact2 closes and discharges C ready for the next operation. The discharging surge can conveniently 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 to1000 operations.
