GB2192096A

GB2192096A - Circuit breaker

Info

Publication number: GB2192096A
Application number: GB08613263A
Authority: GB
Inventors: Peter William Bowen
Original assignee: Crabtree Electrical Industries Ltd
Current assignee: Crabtree Electrical Industries Ltd
Priority date: 1986-05-31
Filing date: 1986-05-31
Publication date: 1987-12-31
Also published as: HK19691A; GB8613263D0; EP0248342A3; EP0248342A2; DE248342T1; ZA873795B; GB2192096B; SG91190G

Abstract

A miniature circuit breaker comprises two arc runners (20, 22) which diverge towards an arc stack (24), onto which an arc is transferred as contacts of the circuit breaker are opened. A supplementary runner (30) is provided, onto which the arc is transferred from the first of said runners (20), so that the arc extends between the second runner (22) and the supplementary runner (30). The supplementary runner (30) is connected into the circuit through a high impedence, so that the rate of increase of arcing current is reduced as the arc travels into the arc stack. <IMAGE>

Description

1 GB2192096A 1 SPECIFICATION objects of this invention to provide a means

by which the arc may be extinguished more Improvements relating to circuit breakers rapidly than is presently practiced.

According to this invention there is provided Description of Invention 70 a circuit breaker of the kind specified wherein

A conventional circuit breaker (hereinafter re- the arc is transferred to an arc runner which ferred to as being of the kind specified) comprovides a higher impedence to the flow of prises a first contact (conventionally fixed) and electric current.

a second contact movable relative to the first The said arc runner may be electrically con- between an open position and a closed posi- 75 nected into the circuit at a point therein on tion, a manually operable control member to the side of the solenoid which is remote from move the movable contact between open and the fixed contact.

closed positions, and a tripping mechanism to The said arc runner may be afforded by a move the movable contact from its closed to supplementary runner, to which the arc is its open position in the event of an overload. 80 transferred from a primary runner integral with Conventionally the tripping mechanism com- the fixed contact.

prises two overload devices to open the cir- Preferably there is not direct physical con- cuit in the event of overload. nection between the primary arc runner and The first of these is a bimetal device the said supplementary arc runner.

temperature of which rises under overload 85 Preferably the added impeclence is provided conditions, and which moves in consequence with a circuit element which produces addi of such temperature rise to open the switch, tional pressure on the arc to move towards usually under the action of a spring. However the arc stack, advantageously in the form of such devices are slow to operate and are an additional coil, the magnetic field of which used only to open the circuit under moderate 90 is effective to force the spark towards the arc overloads. stack.

On short circuit overloads a solenoid device According to this invention there is also is used, through which current passing provided a method of increasing the breaking through the circuit breaker flows, and which, capacity of a circuit breaker by the use of an under short circuit conditions, produces a 95 arc runner providing a significantly higher im magnetic field to move a tripping element pedence to the flow of current, whilst provid (conventionally termed a "slug") to open the ing a means by which the arc is subjected to switch, the slug moving to delatch a tripping a force causing it to remain in the arc stack.

mechanism and physically to move the mov- The arc runner which provides a significantly able contact to an open circuit position. 100 high impedance may be afforded by a supple- Circuit breakers are limited by the current mentary arc runner, to which the arc is trans overload they can accommodate and still be ferred, said means being operative to subject re-usable, the current overload being known the arc to a force tending to cause it to trans as the "breaking capacity". This however ne- fer to said supplementary arc runner and to- cessitates that the circuit breaker be capable 105 wards the arc stack.

of moving to an open circuit condition in a There will now be given a detailed descrip very short time (typically 5 milliseconds). tion, to be read with reference to the accom- On the movement of a conventional circuit panying drawings, of a circuit breaker which is breaker to an open condition under short con- the preferred embodiment of this invention, ditions, the movable contact is physically 110 having been selected for the purposes of illus moved away from a fixed contact at high tating the invention by way of example.

speed. However current still passes between In the accompanying drawings:

the contacts in the form of an arc, and con- Figure I is a schematic view of a conven ventionally the circuit is arranged so that the tional circuit breaker; arc is subjected to pressure to move from the 115 Figure 2 is a schematic view of the circuit two contacts onto "arc runners", which breaker which is the preferred embodiment of diverge and lead the arc into an arc stack, at this invention; and which the are is extinguished. Figures 3 and 4 are enlarged views of part Thus, a conventional circuit breaker, one arc of the preferred embodiment.

runner is electrically integral with the fixed 120 The circuit breaker shown in Fig. 1 is of the contact, and the other is engaged by the kind specified, comprising a housing 6 in movable contact on tripping. which is located a fixed contact 8, a movable Whilst adequate magnetic forces may be contact 10, and a manually operable control generated by the solenoid to disengage the member 12 to move the contact 10 between movable contact from the fixed contact in su- 125 its open and closed positions. Located within fficiently short periods of time, increasing the the housing is overload mechanism, compris breaking capacity of circuit breakers is preing in series a bimetal device 14 and a sole sently limited by the difficulties of transferring noid device 16, the solenoid device 16 com the arc to the arc runners and quenching in - prising a coil 18.

the arc stack, and it is one of the various 130 Integral with the fixed contact 8 is a first 2 GB2192096A 2 arc runner 20, and engaged by the second desirably relatively large gaps (shown at 34) contact 10 when it moves to its open posi- ensure that metal particles carried on the arc tion is a second arc runner 22, which runners do not become fused to the arc runner sys diverge from their contacts towards an arc tem to provide a short circuit between the stack 24. The circuit breaker comprises termi70 primary and supplementary runner.

nals 26 and 28, and the primary circuit ex- It has been found that by this relativey sim tends from the terminal 26 to the movable ple expedient, the time in which an otherwise contact 10, the fixed contact 8, the coil 18, conventional circuit breaker may terminate the the bimetal element 14, and the terminal 28. flow of electric current may significantly be In known manner when the circuit protected 75 reduced, and the breaking capacity of the cir by the breaker is subjected to a moderate and cuit breaker increased.

continuing overload, the element 14 deflects

Claims

under temperature rise, and causes the tripp- CLAIMS ing mechanism (not

shown) to move the con- 1. A circuit breaker of the kind specified tact 10 to its open position. Under severe 80 wherein the arc is transferred to an arc runner overload conditions, such as short circuit, the which provides a higher impedence to the magnetic field produced by the coil 18 causes flow of electric current.

a tripping element to move rapidly to trip the
2. A circuit breaker according to Claim 1 control mechanism, and physically to move wherein the arc runner is electrically connected the contact 10 towards its open position. Any 85 into a circuit at a point therein on the side of arc which is established between the contacts the solenoid which is remote from the fixed 8 and 10 is moved by flux pressure (the flow contact.

path being in the form of a U) onto the arc
3. A circuit breaker according to one of runners 20 and 22, and into the arc stack 24 Claims 1 and 2 wherein said arc runner is at which the arc is extinguished. 90 afforded by a supplementary runner, to which In the circuit breaker which is the preferred the arc is transferred from a primary runner embodiment of this invention, illustrated in integral with the fixed contact.

Figs. 2 to 4, similar numerals are used to
4. A circuit breaker according to Claim 3 denote like parts. wherein there is no direct physical connection However as distinct from the circuit breaker 95 between the primary arc runner and said sup shown in Fig. 1, in the preferred embodiment plementary arc runner.

the arc runner 20 extends towards a supple-
5. A circuit breaker according to any one mentary arc runner 30, which is not in direct of the preceding claims wherein the added im electrical contact with the runner 20. The sup- pedence is provided by a circuit element plementary arc runner 30 is electrically con- 100 which produces additional pressure on the arc nected into the circuit at a point therein on to move towards the arc stack.

the side of the solenoid coil 18 which is re-
6. A circuit breaker according to Claim 5 mote from the fixed contact 8, preferably at a wherein the circuit element is in the form of point between the solenoid coil 18 and the an additional coil, the magnetic field of which bimetal element 14. However between the 105 is effective to force the spark towards the supplementary arc runner 30 and its connec- arc.

tion into the primary circuit, a high impedence
7. A method of increasing the breaking element 32 is provided, specifically in the capacity of a circuit breaker by the use of an form of a secondary coil preferably wound arc runner providing a significantly impedence around one of the formers of the solenoid 16. 110 to the flow of current, whilst providing a The high flux density in the circuit loop adja- means by which the arc is subjected to a cent to the movable and fixed contacts as is force causing it to remain in the arc stack.

established during arcing conditions can cause
8. A method according to Claim 7 wherein the arc to be transferred onto the existing arc the arc runner which provides a significantly runners 20 and 22 without difficulty, causing 115 higher impedence is afforded by a supplemen the arc to be accelerated towards the supple- tary are runner, to which the arc is trans mentary runner 30 and the arc stack 24. ferred, said means being operative to subject However transference of the arc between the arc to a force tending to cause it to trans the arc runners 22 and 30 is effective to aid fer to said supplementary are runner and to- rapid extinction of the arc. Further, the mag- 120 wards the arc stack.

netic field generated by the coil 32 can be
9. A circuit breaker constructed and ar- such as similarly to exert pressure to hold the ranged substantially as hereinbefore described arc in the arc stack to be extinguished. with reference to Figs. 2, 3 and 4 of the As will be seen in Fig. 3, the secondary coil accompanying drawings.

32 is preferably provided of high resistivity 125
10. A method of increasing the breaking ferrous material, providing not only a high recapacity of a circuit breaker, when carried out sistence in the ciruit but also producing a high substantially as hereinbefore described with magnetic field. As will be seen in Fig. 4, reference to Figs. 2, 3 and 4 of the accom whilst the primary runner 20 necessarily panying drawings.

passes close the supplementary runner 30, 130
11.Any novel feature or novel combination 3 GB2192096A 3 of features as hereinbefore described and/or as shown in the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.