An arc extinguisher

Abstract

 An arc extinguishing arrangement (10) has a stack of a number of paired plates (48) formed from sheets, each bent into a "U". The space between each set of paired plates is filled with an electrically insulating material (54).

Description

[0001] THIS INVENTION relates to circuit breakers and to arc extinguishing arrangements therefor.

[0002] According to the invention there is provided an arc extinguishing arrangement for a circuit breaker, which includes
a plurality of plates that are of an electrically conducting material and which are arranged in a series, with the plates substantially parallel to one another and with at least two adjacent plates being paired and being electrically connected.

[0003] Preferably, there is an even number of plates and all the plates are paired, with a first plate being paired with a second plate, a third plate being paired with a fourth plate, and so on. Further, the paired plates may be electrically connected at their leading ends. This may be accomplished by electrically connecting the paired plates by means of a connector, or the plates may be formed from one piece of sheet material that is bent over to form a "U", the base of the "U" forming the leading end.

[0004] The space between paired plates may be empty so that there is a vacuum between them, or they may be filled by a gas such as air, or they may be filled by spacer members that are of an electrically insulating material.

[0005] The leading portion of each pair of plates, constituted by the base of the "U" may be continuous, or it may have a recess or indentation therein. Thus, the Applicants believe that it may be advantageous to have a notch or the like extending into the plates from their leading ends.

[0006] The plates may be of a ferro-magnetic material.

[0007] An arc extinguishing arrangement as described above may then be utilized in a circuit breaker with the electrically leading ends of the plates facing towards the contacts of the circuit breaker.

[0008] Thus the invention extends still further to a circuit breaker which includes an arc extinguishing arrangement as des­cribed above.

[0009] More particularly the arrangement may be located between arc runners of the circuit breaker.

[0010] It will be appreciated by those skilled in the art that as soon as an arc is created and blown between a first arc runner which is electrically connected with a stationary contact of the breaker and the first plate that is closest to it, an electric current is caused to flow in this first plate. Since paired plates are electrically connected at their leading ends, arc current is forced to flow along the first plate towards its leading end and then along the second plate before a second arc can be created between the second and third plates, and so on. Those skilled in the art will readily appreciate that the current in one plate is in an opposite direction to its paired plate and to an adjacent plate so that a force is exerted on the individual arcs formed between adjacent non paired plates so that the arcs are rapidly accelerated away from the contacts towards an arc vent. Further, as arc current flows through the plates, the circuit resistance increases because the length of the flow path increases. This has the effect of reducing the arc current, which may be reduced even further by making the plates of a material having a suitably high resistivity. Furthermore, the relatively large area of the plates assists in cooling the arcs.

[0011] The invention is now described, by way of an example, with reference to the accompanying drawings in which:-

Figure 1 shows schematically an arc extinguishing arrange­ment and a circuit breaker in accordance with the invention where the arc is electromagnetically blown into the arc extinguisher;

Figure 2 shows schematically in more detail, the profile of leading edges of arc extinguishing plates of the arc extinguishing arrangement of the breaker of Figure 1;

Figure 3 shows schematically an arc extinguishing arrange­ment in accordance with the invention with a reverse loop line terminal, the arc being generated inside the arc extinguisher;
and

Figure 4 shows schematically an arc extinguishing arrange­ ment with a linear line terminal, in which the arc is also generated inside the arc extinguisher.

[0012] Referring to Figure 1 a circuit breaker is shown therein, designated generally by reference numeral 10, The cir­cuit breaker 10 has a moving contact carrier 12 which carries a moving contact 14. The moving contact 14 engages a stationary contact 16. The circuit breaker 10 further has a first terminal assembly 18 whereby a cable or the like may be connected to the breaker. The terminal assembly 18 is electrically connected with the contact carrier 12 by means of a flexible strap 20 via a bi­metal strip 22 and other components. The circuit breaker 10 also has a second terminal arrangement 24 which is electrically connected with the stationary contact 16 via a stationary conduc­ting link element 26.

[0013] As is clearly shown in Figure 1, the link element 26 has a linear portion 28 adjacent to the stationary contact 16, an intermediate curved portion 30 and a linear portion 32 which is adjacent the second terminal assembly 24.

[0014] The contact carrier 12, similarly, has a section 34 with a linear profile adjacent its contact 14 extending away from the contact 14 in the same direction as the linear portion 28 of the link element 26, to be parallel thereto and to be as close as possible while still providing for adequate electrical insulation. The linear section 34 intersects a further linear section 36 which is angled towards the link element 26. It will be appreciated that the sections 34 and 36 are between the contact 14 and the strap 20, so that current flows through the contact carrier 12 to the contact 14, through the contact 16 and then through the link element 26. Thus, current flow in the contact carrier 12 and in the link element 26 are substantially parallel to one another and in opposite directions so that the magnetic fields generated thereby assist one another and, in use, would apply a force on an arc between the contacts 14 and 16 displacing the arc away from the contacts.

[0015] The contact carrier 12 also has a nose portion 38 that extends away from the contact 14 towards a reverse arc runner 40. Thus, when the contact carrier 12 is displaced so that its con­tact 14 moves away from the stationary contact 16, the nose portion 38 comes sufficiently close to the reverse arc runner 40 for current to be transferred to the reverse arc runner 40. The reverse arc runner 40, in turn, is also electrically connected with the first terminal assembly 18. Thus, the nose portion 38 becomes an extension of the reverse arc runner 40.

[0016] The circuit breaker 10 also has a line arc runner 42 that extends from the stationary contact 16 and is formed in one piece with the link element 26. Between the arc runners 40 and 42 there is an arc chute area 44. In the arc chute area is an arc extinguishing arrangement 46. This arrangement 46 comprises five sets of paired plates 48. Each set of paired plates 48 is formed from a sheet of a suitably electrically conducting mate­ rial that is also ferro-magnetic. Each sheet is bent into a 'U' which is very narrow such that the length of the legs thereof is much longer than the spacing therebetween. Thus, each paired set 48 comprises two parallel plates 50 and 52 connected by a leading edge portion 56. As is clearly seen in Figure 1, the leading edge portions 56 face towards the contacts 14 and 16. The space between the plates 50 and 52 of each set 48 is filled by a suitably electrically insulating medium which may be a vacuum, a suitable gas, or a suitable material such as is shown at 54. The leading edge portions may be linear and continuous or they may be notched as is indicated at 58 in Figure 2.

[0017] It will be appreciated, in use, that an arc created between the contacts 14 and 16 will be displaced toward the arc extinguishing arrangement 46. When the arc meets the sets 48, an arc will be established between the line arc runner 42 and the adjacent plate 50, between the plate 52 of the bottom most set 48 and the plate 50 of the next set, and so on, with an arc also then being formed between the uppermost plate 52 and the reverse arc runner 40. Currently flow in the arc runners 40 and 42 will create a magnetic field tending to move the arc further between the plates 50 and 52 away from their leading edge portions 56. Thus, current will be caused to flow in the plates 50 and 52, through their leading edge portions 56. The current flowing in the plates 50 and 52, being of opposite direction, will assist one another and strengthen the magnetic field which is displacing the arc towards an arc vent 58. Thus, the arc will be rapidly extinguished and the resistance provided by the plates 50 and 54 will assist in doing so.

[0018] Referring now to Figures 3 and 4, parts of two further circuit breakers 70 and 72 are shown. These circuit breakers 70 and 72 also use the arc extinguishing arrangement 46 which is similarly referenced as in Figures 1 and 2. It will be noted however that the plates 50 and 52 have a slot 74, rather than a notch, so that the carrier 12 can pass therethrough. Thus, whereas the breaker 10 of Figure 1 has a stationary contact 16 spaced from the arc extinguishing arrangement 46, the breakers 70 and 72 have a stationary contact 16 close to the arc extinguishing arrangement 46 and aligned with the bottom-most plate 50, so that in use, the arc is immediately transferred to the plates 50 and 52 without having to be electromagnetically blown into the arc extinguishing arrangement 46. Further, the breaker 70 of Figure 3 has a reverse loop line terminal 76, and the breaker 72 of Figure 4 has a linear line terminal 78.

[0019] Thus, a circuit breaker is provided which has an im­proved short circuit interruption rating and it is possible to reduce the size and cost of contacts therefor. Further, with the arc extinguishing arrangement, an arc is rapidly accelerated, arc current is quickly reduced and arc current is progressively reduced as the arc approaches the arc vent. Further, the arc can be quickly and efficiently extinguished without electromagnetic blow off of the arc.

Claims

1. An arc extinguishing arrangement for a circuit breaker which includes
a plurality of plates that are of an electrically conducting material and which are arranged in a series, with the plates substantially parallel to one another and with at least two adjacent plates being paired and being electrically connected.

2. The arrangement claimed in Claim 1, which has an even number of plates and all the plates are paired, with the plates of each pair being electrically connected.

3. The arrangement claimed in Claim 1 or 2, in which the or each pair of plates are electrically connected along leading ends of the plates.

4. The arrangement claimed in Claim 3, in which at least one pair of plates is constituted by one piece of sheet material that is "U"-shaped.

5. The arrangement claimed in Claim 2, in which each pair has a spacer member that is of an electrically insulating material between its plates.

6. The arrangement claimed in Claim 4, in which the or each pair of plates has a notch extending into the leading ends of the plates.

7. A circuit breaker which includes an arc extinguishing arrangement as claimed in any one of the preceding claims.

8. The circuit breaker claimed in Claim 7, which includes a pair of contacts, and the leading ends of the plates face towards the contacts.

9. The circuit breaker claimed in Claim 7, which includes arc runners, the arc extinguishing arrangement being located between the arc runners.

10. The circuit breaker claimed in Claim 7, which has a stationary contact that is spaced from the arc extinguishing arrangement, such that, in use, an arc generated between the stationary contact and a moving contact must be blown into the arc extinguishing arrangement.

11. The circuit breaker claimed in Claim 7, which has a stationary contact close to the arc extinguishing arrangement such that, in use, an arc generated between the stationary contact and a moving contact is immediately transferred to the arc extinguishing arrangement.

12. The circuit breaker claimed in Claim 11, which the plates of the arc extinguishing arrangement each have a slot, and the breaker has a moving contact carrier which carries the moving contact and passes through the slots.

Drawing