1、BRITISH STANDARD BS 764:1990 Specification for Automatic change-over contactors for emergency lighting systems UDC 621.316.53BS764:1990 This British Standard, having been prepared under the directionof the Power Electrical Engineering Standards Policy Committee, was published underthe authority of t
2、he BoardofBSI and comes intoeffecton 31 May 1990 BSI 10-1999 First published December 1937 Second edition July 1954 Third edition May 1990 The following BSI references relate to the work on this standard: Committee reference PEL/10 Draftannounced in BSI News November 1989 ISBN 0 580 17995 8 Committe
3、es responsible for this British Standard The preparation of this British Standard was entrusted by the Power Electrical Engineering Standards Policy Committee (PEL/-) to Technical Committee PEL/10, upon which the following bodies were represented: ASTA Certification Services Association of Manufactu
4、rers Allied to the Electrical and Electronic Industry (BEAMALtd.) British Gas plc ERA Technology Ltd. Electrical Contractors Association Electrical Installation Equipment Manufacturers Association (BEAMA Ltd.) Electricity Supply Industry in England and Wales Electronic Components Industry Federation
5、 GAMBICA (BEAMA Ltd.) Health and Safety Executive Institution of Electrical Engineers Amendments issued since publication Amd. No. Date of issue CommentsBS764:1990 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Characteristics 1 4 Design
6、, construction and marking 2 5 Tests 5 Appendix A Methods for measurement of temperature 8 Appendix B Information to be supplied to the manufacturer with enquiry and/or order 8 Figure 1 Diagram of typical circuit for test for making and breaking capacity 7 Table 1 Minimum contact force 3 Table 2 Lim
7、its of temperature rise for contacts and conductors 4 Table 3 Limits of temperature rise for coils 5 Publications referred to Inside back coverBS764:1990 ii BSI 10-1999 Foreword This new edition of BS 764 has been prepared under the direction of the Power Electrical Engineering Standards Policy Comm
8、ittee. It introduces technical changes to bring the standard up-to-date and includes references to new materials to eliminate the use of asbestos and asbestos products. This new edition does not reflect a full review of the standard which will be undertaken in due course. This British Standard repla
9、ces BS 764:1954 which is withdrawn. Assessed capability. Users of this British Standard are advised to consider the desirability of assessment and registration of a suppliers quality systems against the appropriate Part of BS 5750 by a third party certification body. A British Standard does not purp
10、ort 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 comprises a front cover, an inside front c
11、over, pages i and ii, pages1 to 8, 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.BS764:1990 BSI 10-1999 1 1 Scope This British Standard speci
12、fies d.c. and single-phase a.c. automatic double-pole change-over contactors for low voltages up to 250 V employed in conjunction with storage batteries or other alternative source of supply, to provide a means of automatically changing the current supplied to safety lights from the normal source to
13、 the alternative source when the normal source fails, and of reconnecting the safety lights to the normal source when this source is restored. This standard does not apply to three-phase a.c. automatic change-over contactors. NOTE 1Appendix B lists information to be supplied to the manufacturer with
14、 the enquiry and/or order. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard, the following definitions apply. 2.1 automatic change-over contactor a complete apparatus for effecting automatic
15、 change-over of the safety lights from the normal supply to the alternative supply when the normal supply fails, and for returning the safety lights to the normal supply when this supply is restored. The return operation may be effected through the agency of a relay which, if employed, is an integra
16、l part of the contactor 2.2 safety lights lights which are normally connected to normal supply and are changed over to the alternative supply when the normal supply fails, e.g. the safety lights specified under the Cinematograph Regulations 2.3 main contactor apparatus constructed in accordance with
17、 this specification, excepting the relay if employed. Where the complete automatic change-over contactor is intended, this is made clear in relevant clauses 2.4 relay a voltage dependent relay, the function of which is to cause the main contactor to change from the emergency to the normal position w
18、hen the main supply voltage has recovered to a particular value 2.5 contactor coil the shunt connected coil energized from the normal supply, which causes the main contactor either to change to, or to remain in, the normal position 2.6 relay coil the shunt connected coil, energized from the normal s
19、upply, which causes the relay contacts to move to one of their two positions 2.7 load carrying contacts contacts on the main contactors which in either normal or emergency conditions carry the current for supplying the safety lights 2.8 “silver” contact a contact composed of or faced with not less t
20、han0.4064 mm of fine silver or other material of equivalent performance 2.9 normal position of main contactor the position of the main contactor when it is connecting the safety lights to the normal supply 2.10 emergency position of main contactor the position of the main contactor when it is connec
21、ting the safety lights to the emergency supply 2.11 dust-protecting enclosure an enclosure constructed to prevent the ready ingress of dust 3 Characteristics 3.1 Rating The complete apparatus shall be rated in terms of its current-carrying capacity and voltage and also in terms of frequency if a.c.
22、3.2 Sizes The following current ratings shall apply: a) 15 A at 30 V; b) 15 A, 30 A, 60 A and 100 A at voltages not exceeding 250 V. Where a total load in excess of 100 A applies, it should be divided over two or more separate circuits, each controlled by an independent automatic change-over contact
23、or.BS764:1990 2 BSI 10-1999 4 Design, construction and marking 4.1 General principles The apparatus shall operate on the principle that the contacts of the main contactor are closed to the normal position by an electro-magnet or electro-magnets, energized from the normal supply, the direct pull of w
24、hich is the only force preventing the main contactor from closing to its emergency position under the action of gravity or springs, or both. Every operating spring used shall be so fitted that in the event of breakage, it shall not foul the mechanism and shall not come into contact with live parts.
25、The use of a relay is permitted in conjunction with the main contactor. NOTEThe principles above do not refer to contact springs. The following types of contactor are beyond the scope of this British Standard: a) automatic change-over contactors in which the connection of the normal and alternative
26、supplies is separately effected by two distinct contactors interlocked mechanically or electrically, or mechanically and electrically; b) contactors dependent on electrical energy to force them into or maintain them in the emergency position; c) contactors dependent on the application of electrical
27、energy to release them from their normal position, or any switch employing toggles, latches, triggers, locks or similar devices, toothed gearing or ratchet action, to hold them in any position. 4.2 Mounting The contactor shall be suitably insulated and mounted on bars or a panel. The bars or panel s
28、hall be of ample stiffness and strength. Where a panel is used, it shall be of phenolic resin bonded laminate in accordance with BS 2572. 4.3 Spacing The spacing between the various poles of the main contactor shall be adequate for the voltage and current which are to be interrupted when tested in a
29、ccordance with 5.2.5. 4.4 Contacts Contacts, including auxiliary contacts (see 4.11) shall be of such a type that they do not exert, by reason of their construction or design, any force opposing the movement of the contact in the direction of breaking contact from either the normal or emergency posi
30、tion. NOTEContacts of the knife-switch type do not comply with the above requirements, and contactors using knife-switch type contacts are therefore beyond the scope of this British Standard. Where “silver” contacts are fitted on contactors with ratings not exceeding 30 A, the double break bridge ty
31、pe of contact may be used. 4.5 Contact force 4.5.1 Hinged or pivoted contacts. With the contactor fully closed in each position the force required to pull any contact finger off the fixed contact, as measured by a spring balance attached at the line of contact, in the direction of motion of the movi
32、ng contact at the moment it is moving away from the stationary contact, shall be not less than the values given in the appropriate column, 3 or 4, of Table 1. 4.5.2 Double break bridge contacts. Where the double break bridge type of contact is used, the pressure on each contact of any one pole shall
33、 be sensibly equal, and the total force exerted by the common spring, with the contactor fully closed in each position, shall be not less than the values given in column 5 of Table 1. 4.6 Change-over voltage 4.6.1 The main contactor shall operate so that the poles of the safety lighting load are aut
34、omatically disconnected from the normal supply and connected to the alternative supply when the voltage of the normal supply has failed or has fallen below 60 % of the nominal voltage of the normal supply with the contactor coil at its normal working temperature. 4.6.2 The automatic change-over cont
35、actor (including relay if any) shall require not more than85 % of the nominal voltage of the normal supply to bring about reconnection of the safety lights to the normal supply. 4.6.3 Operation of the contactor in accordance with4.6.1 and 4.6.2 shall be proved by testing in accordance with 5.2.7 and
36、 5.2.8. 4.6.4 The contactor shall remain fully closed in either position as determined by 4.6.1 and 4.6.2 until change-over occurs and the contactor changes to the alternative fully closed position. The pressure between the contacts, closed in the above manner, shall be maintained at a value not les
37、s than that specified in 4.5.1 or 4.5.2 whatever the voltage of the normal supply may be, i.e. no matter how slowly the voltage of the normal supply may rise or fall, there shall not, in either position, be a weakening of contact pressure below the minimum required by4.5.1 or 4.5.2, as appropriate.
38、4.7 Sequences of operation Both poles of the supply shall, by the action of the main contactor, be disconnected from the safety lights before these are connected to the alternative supply, conversely, it is essential that the safety lights be disconnected from the alternative supply before being rec
39、onnected to the normal supply.BS764:1990 BSI 10-1999 3 Table 1 Minimum contact force When the normal source of supply is d.c. and the alternative source is a battery, the latter may be connected to it (through a resistance, if desired) for trickle or other charging, providing that by the action of t
40、he automatic contactor the normal supply is effectively disconnected from both battery and lights on both poles when the normal supply has failed or has decreased in voltage as described in4.6.1. 4.8 Polarity of contacts If both the normal supply and the alternative supply are d.c., the polarities o
41、f the terminals shall be suitably marked to ensure that the positive and negative load connections retain the same polarity on either supply. 4.9 Contact separation There shall be an effective break on each pole of the main contactor to ensure compliance with the test prescribed in 5.2.5. 4.10 Stabi
42、lity of operation The main contactor shall be free from chattering, and shall change over without appreciable bounce of the contacts which are closing. The design shall be such that there shall be no possibility of hunting upon rise and fall of voltage, however slowly such change may take place. Whe
43、n the armature of the main contactor is in the closed position, and the full voltage at normal frequency is applied to the coil (in series with associated economy resistances if any), the contactor shall not give out more noise than the hum associated with any properly constructed laminated core hav
44、ing tightly clamped laminations and carrying an a.c. flux. NOTEThe noise of the main contactor is governed to a considerable extent by the particular method used for its installation or enclosure. If it is desired to reduce the noise, rectified a.c. may be used for energizing the coil or coils, or o
45、ther means may be adopted provided that they in no way conflict with the terms of this specification. 4.11 Auxiliary contacts In addition to the load-carrying contacts of the main contactor carrying the safety lighting load, there may be auxiliary contacts for: a) use with the economy resistor of th
46、e contactor coil; b) an alarm signal; c) disconnecting charging circuits; d) operation of other external circuits not part of the safety lighting load. 4.12 Voltage relay If a voltage relay is used to form part of the complete change-over contactor, it shall comply with the following. a) The relay s
47、hall be so connected that its coil is energized from the normal supply, and shall be so arranged and connected that its contacts permit the operating coil of the main contactor to be effectively energized only when the normal supply has been restored to the value specified in4.6.2. The coil of the m
48、ain contactor may, however, be partially energized through the economy resistance before being fully energized, subject to compliance with 4.6.4. b) When the main contactor has moved into the normal position, the coil of the relay shall be de-energized, the relay not being required to operate until
49、the automatic change-over contactor is once more in the emergency position with the condition a) above applying. 1 2 3 4 5 Rated voltage Rated current Minimum force Hinged or pivoted contacts (see 4.5.1) Total force on double break bridge contacts (see 4.5.2) Copper contacts “Silver” contacts “Silver” contacts V A N N N above 24 and up to 250 15 2.2 1.1 1.1 30 3.3 2.2 2.2 any voltage up to 250 60 9.0 3.3 100 18.0 6.6 BS764:1990 4 BSI 10-1999 c) The relay used shall be of substantial and sound design and shall be capable of passing the relevant tests speci
