Circuit breaker with selective protection

Abstract

The invention relates to a circuit breaker with selective protection. The circuit breaker has a main electrically conductive path and a current-limiting electrically conductive path between a set of incoming line terminals and a set of outgoing line terminals, wherein the current-limiting electrically conductive path is connected in parallel with the main electrically conductive path. The main electrically conductive path comprises a breakpoint, a compression bar and a magnetic starter, the current-limiting electrically conductive path comprises a breakpoint, a bimetallic strip, a current-limiting resistor, and a shunt resistor, wherein the current-limiting electrically conductive path is connected in parallel with the main electrically conductive path between the incoming line terminals and the outgoing line terminals, the bimetallic element and the current-limiting resistor are connected in series in the current-limiting electrically conductive path, and two ends of the bimetallic element is connected in parallel with the shunt resistor. According to the invention, in the protection process of the selective protection circuit breaker, current flowing through the bimetallic strip when a short circuit exists can be reduced to protect the bimetallic strip from inferiority permanent deformation so as to prolong life endurance of the short circuit protection effectively.

Description

technical field [0001] The invention relates to a circuit breaker with selective protection, which belongs to the field of low-voltage electrical appliances. Background technique [0002] In the patent application No. 201020265871.3, a circuit breaker with selective protection is proposed. The circuit breaker "connects the second breakpoint in series between the second group of incoming line terminals and the outgoing line terminals and the electromagnetic start of the drive magnetic release. Coil, between the second group of incoming line terminals and the electromagnetic starting coil, a parallel path composed of the third breakpoint, thermal release and resistance in series is connected in parallel"; "When a short-circuit current occurs in the circuit, the electromagnetic starting coil 5 acts For the corresponding moving contact 202, the corresponding second breakpoint 2 is opened, while the other breakpoints 2 are still kept in the closed position, so the short-circuit c...

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Problems solved by technology

"Under the short-circuit current of 7 times the set current, the time for the current to flow through the bimetal is about 80 milliseconds, and the time for the current to flow through the bimetal is also close to 20 milliseconds under the short-circuit current of 20 times the set current and greater. Milliseconds, however, after several short-circuit tests, it was found that in this case, the bimetal would be permanently deformed and the protection time range would exceed the calibrated value

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