GB2285889A

GB2285889A - Circuit breaker

Info

Publication number: GB2285889A
Application number: GB9419930A
Authority: GB
Inventors: Thomas O'carroll; Desmond Regan; Dermot Hurst; Didier Lebouc
Original assignee: Merlin Gerin SA; Square D Co
Current assignee: Merlin Gerin SA; Schneider Electric USA Inc
Priority date: 1994-01-21
Filing date: 1994-10-04
Publication date: 1995-07-26
Also published as: EP0745264A1; CA2181726A1; AU1545295A; MX9602929A; WO1995020237A1; GB9419930D0

Abstract

A circuit breaker 1 comprises an enclosed arc chamber 50 into which arc gases generated on tripping of the breaker under load are exhausted. The arc chamber 50 is defined by a longitudinal dividing wall 51 in a housing defined by a base and cover, a portion of the rear wall of the housing and a transverse dividing wall 53. The am gases enter the chamber 50 through an aperture 52 and are prevented from exiting the breaker. This eliminates cross-phasing in the load centre in which the circuit breaker is mounted. <IMAGE>

Description

"A Circuit Breaker" The invention relates to a circuit breaker.

Circuit breakers are used to break an electrical circuit between a source of electricity and an electrical load in response to a fault condition. Generally the circuit breaker includes a stationary contact coupled to the electrical load and a movable contact coupled to the electrical source. In the event of a fault the circuit breaker opens the contacts. An arc is generated which is generally directed by an arc arrester plate and an arc deionization stack to exhaust from the rear of the circuit breaker. Generally, a number of circuit breakers are arranged in a load centre having a number of bus bars to which the circuit breakers are mounted. The bus bars require to be protected against contact with the arc gases as the gases are ionised and can lead to short circuits between phases (known as cross-phasing) if the gases contact with the unprotected busbars.

This invention is directed towards providing an improved circuit breaker which will overcome this difficulty.

According to the invention there is provided a circuit breaker having an enclosed arc chamber into which arc gases generated on tripping of the breaker under load are exhausted and retained within the chamber.

In one particular embodiment of the invention the breaker includes a housing defined by a base, a cover, a rear wall, a front wall, and upper and lower side walls extending between the front and rear walls, the enclosed arc chamber being defined within the housing.

In one embodiment of the invention the arc chamber is provided adjacent the rear wall of the housing.

In a particularly preferred arrangement the arc chamber includes a longitudinally extending dividing wall spacedapart from the rear wall and separating the chamber from components of a circuit breaking device, the longitudinal dividing wall having an inlet for delivery of arc gases into the chamber.

Preferably the inlet is provided remote from the generation of the arc within the housing.

In one embodiment of the invention the chamber is defined by a transversely extending dividing wall which extends between the rear wall of the housing and the longitudinally extending dividing wall.

Preferably the or each dividing wall comprises a cover portion extending from the cover and a base portion extending from the base to engage with the cover portion.

Most preferably the cover portion and base portion of the dividing wall interengage to define the enclosed chamber on assembly of the cover to the base.

In a preferred arrangement the length of the chamber is at least 40% of the length of the rear wall.

The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a view of a circuit breaker according to the invention; Fig. 2 is a perspective view of a base of the circuit breaker; Fig. 3 is a perspective view of a cover of the circuit breaker; and Fig. 4 is a perspective view of a detail of the circuit breaker; and Fig. 5 is a cross sectional view of another detail of the circuit breaker.

Referring to the drawings, there is illustrated a circuit breaker 1 including a line terminal 2 for coupling to a source of electricity and a load terminal 3 for coupling to a load. The current path includes a coil 4 and an arc runner 6. An arc stack 5 assists in breaking any arc formed when contacts 7 are separated under load. The contacts 7 may be separated in response to operation of a bimetal 10. The bimetal 10 is adjusted by means of a calibration screw 12. The coil 4 causes separation of the contacts 7 in the event of a current surge.

The circuit breaker 1 comprises a base 20 and a cover 21.

The base 20 and cover 21 both have rear wall portions 22a, 22b respectively, front wall portions 23a, 23b, upper sidewall portions 24a, 24b and lower sidewall portions 25a, 25b respectively which cooperate on assembly of the base 20 and cover 21 to form an enclosure for the various components of the circuit breaker.

Upper and lower mounting devices 26, 27 extend from the rear of the housing.

The circuit breaker 1 includes an enclosed arc chamber 50 into which arc gases generated on tripping of the breaker under load are exhausted. The chamber 50 is defined by a longitudinally extending dividing wall 51 which includes an inlet 52 for arc gases. A transverse dividing wall 53 extends between the longitudinal dividing wall 51 and the rear wall 22a,22b of the housing approximately half-way along the rear wall. Preferably the length of the chamber 50 is at least 40%, and most preferably at least 50% of the length of the rear wall 22a,22b.

The longitudinal dividing wall 51 comprises a base portion Sla and a cover 51b which have interengaging portions 60a,60b which interengage as illustrated in Fig. 5 on assembly of the base 20 and cover 21. Similarly, the transverse dividing wall 53 comprises a base portion 53a and a cover portion 53b which have angled mating surfaces 61a, 61b for interengagement as illustrated in Fig. 5 on assembly of the base 20 and cover 21. In this way an effective enclosed chamber 50 is formed.

The flow of arc gases following short circuit interruption and separation of the contacts is illustrated by arrows in Fig. 1. It will be noted that the arc is directed through the arc stack by the arc runner. The debris and gases are then lead by various deflecting walls in the housing to the inlet 52 of the arc chamber 50. The gases are confined within the chamber 50 and are thus prevented from exiting the breaker. This eliminates cross-phasing in the load centre in which the breaker is mounted. The arc chamber 50 is created within the boundaries of the circuit breaker housing which results in exhaust gases which can carry considerable debris from contact erosion being retained within the enclosed chamber 50. Because an external outlet for the gases is not required the housing may be effectively sealed to prevent dust ingress.

It is also anticipated that the performance of the circuit breaker will be improved because the chamber 50 creates a back pressure for the arc gases. Tests to date have indicated an improved performance under short circuit conditions when the gases vent into closed chamber 50.

It will be appreciated that while the invention has been described with reference to a miniature circuit breaker, it will be appreciated that it may be applied to any type of circuit breaker including a moulded case circuit breaker or other devices in which arc gases are generated.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail.

Claims

CLAIMS:

1. A circuit breaker having an enclosed arc chamber into which arc gases generated on tripping of the breaker under load are exhausted and retained within the chamber.

2. A circuit breaker as claimed in claim 1 wherein the breaker includes a housing defined by a base, a cover, a rear wall, a front wall, and upper and lower side walls extending between the front and rear walls, the enclosed arc chamber being defined within the housing.

3. A circuit breaker as claimed in claim 2 wherein the arc chamber is provided adjacent the rear wall of the housing.

4. A circuit breaker as claimed in claim 3 wherein the arc chamber includes a longitudinally extending dividing wall spaced-apart from the rear wall and separating the chamber from components of a circuit breaking device, the longitudinal dividing wall having an inlet for delivery of arc gases into the chamber.

5. A circuit breaker as claimed in claim 4 wherein the inlet is provided remote from the generation of the arc within the housing.

6. A circuit breaker as claimed in claim 4 or 5 wherein the chamber is defined by a transversely extending dividing wall which extends between the rear wall of the housing and the longitudinally extending dividing wall.

7. A circuit breaker as claimed in any of claims 4 to 6 wherein the or each dividing wall comprises a cover portion extending from the cover and a base portion extending from the base to engage with the cover portion.

8. A circuit breaker as claimed in claim 7 wherein the cover portion and base portion of the dividing wall interengage to define the enclosed chamber on assembly of the cover to the base.

9. A circuit breaker as claimed in any of claims 2 to 8 wherein the length of the chamber is at least 40% of the length of the rear wall.

10. A circuit breaker substantially as hereinbefore described with reference to the accompanying drawings.