US2904660A - Air blast circuit breakers - Google Patents

Description

Sept. 15, 1959 FQRWALD I 2,904,660

AIR BLAST CIRCUIT BREAKERS Filed March ll, 1958 a l||l INVENTOR. Haakon Earn/a Zd United States Patent AIR BLAST CIRCUIT BREAKERS Haakon Forwald, Ludvika, Sweden, assignor to, Allmiinna Svenska Elektriska Aktieboiaget, Vasteras, Sweden, a corporation of Sweden Application March 11, 1958, Serial No. 720,727

Claims priority, application Sweden March 15, 1957 3 Claims. (Cl. 200-148) Sometimes a persisting breaking arc can occur in compressed air circuit breakers. This happens if the breaker is exposed to short-circuiting effects higher than the effect it was rated for. Such a persisting arc causes more or less serious damage to the elements inside the circuit breaker due to the heat produced by the arc. Even if the risk of explosions can be avoided by arranging a safety membrane, a persisting are always means a serious drawback because the breaker is considerably damaged, and the present invention relates to an arrangement for avoiding such damage. The invention is mainly characterized in that the breaker is provided with a member which, at the occurrence of such a pressure as that produced by the persisting arc, immediately closes the breaker and leaves it to other breakers present in the network to take care of the interruption of the shortcircuiting eifect. The invention is further characterized by the fact that this member opens the operating circuit performing the opening of the breaker, so that there is no risk of the breaker being opened again before the fault has been eliminated and the damaged parts have been replaced.

On the accompanying drawing, Fig. 1 shows schematically a circuit breaker with an arrangement according to the invention for preventing the formation of a persisting arc, and Fig. 2 shows in detail the design of members performing the recoupling of the breaking gap at the occurrence of breaking arcs. On the drawing, 1 designates a compressed air container to which a pillar insulator 2 is attached carrying a further compressed air container 3, in which a leading through insulator 4 and an operating member 5 are located. The insulator 4 carries the stationary contact and the operating member 5 carries the movable contact in the breaking gap. The movable contact is operated by aid of compressed air which is supplied through a pipe line 6. This pipe line is connected with a valve 7, which is joined with the compressed air container 1, and the valve 7 is operated by both magnet coils 8 and 9, which are supplied with current over the contacts 10, 11, respectively. The coil 8 serves for closing the breaker while the coil 9 serves for opening the breaker. The contacts 10 and 11, in their turn, are operated by a member 12 attached in the compressed air container 1. Besides there are buttons 13 and "ice 14 for manually closing and opening the circuit breaker. The pressure sensitive member 12 consists of a cylinder 15, in which a piston v16 is movably arranged, which is actuated by a spring 17 counteracting the air pressure. The piston 16 is provided with a rod 18, which acts on a catch 19, which in its turn acts on a rod 20, which, under the influence of a spring 21, tends to move downwards when the catch 19 does not engage the hook on the rod 20. The rod 20 is arranged to engage at its movement the contacts 10 and 11, respectively, by being provided with contact bridges 22 and 23 which close the contacts 10 and 11, respectively.

The arrangement acts in such a way that, if due to a persisting are between the main contacts in the compressed air container 3, a heating should take place so that the pressure in the container will exceed a certain value, the piston 16 is moved to the right. Then the rod 18 pushes the catch 19 sideways, so that the rod 20 is released and moved downwards by the spring 21, so that the contact bridges attached to the rod close the closing contacts 10 and open the opening contacts 11. This safety device consisting of the cylinder 15 with the piston 16, the catch 19 and contact rod 20 is normally arranged in such a way that it can only be put back into its original position manually, but of course nothing prevents if from being moved back automatically, but this can of course only be performed when the circuit breaker has been inspected and has proved to be quite all right.

I claim as my invention:

1. Arrangement in an air blast circuit breaker for preventing persisting arcs between the breaking contacts, comprising a compressed air container, operating members for the circuit breaker, and a pressure sensitive member so connected with the said container that an increase in pressure within the said container due to the heat generated by the arc causes the said sensitive member to so actuate the said operating members that the circuit breaker is closed.

2. Arrangement according to claim 1, characterized in that the pressure sensitive member is a cylinder which is connected to the compressed air container and contains a piston actuated by a spring, which piston under the influence of a certain increase of pressure, actuates the operating members of the circuit breaker in closing direction and blocks its members in opening direction.

3. Arrangement according to claim 2, characterized in that the piston at its movement actuates a catch in such a manner that this releases a rod actuated by a spring, which rod carried two contact bridges, one of these being arranged to close the current circuit for closing the breaker and the other one for interrupting the operating members of the circuit breaker for its opening.

References Cited in the file of this patent FOREIGN PATENTS 477,693 Germany June 12, 1929

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