On Circuit Breaker

Published:2011/3/21 22:59:00 Author:LiuQiaoyan From:SeekIC

A circuit breaker is an electrical switch that works automatically to prevent the electrical circuit from damaging by overload and short circuit. The operational principle is to detect a fault condition and then discontinue the flow by interrupting the continuity. A circuit breaker can be reset to resume normal operation unlike fuse that has to be replaced after operates once. Circuit breakers are various in size, from small devices for individual household appliance to large switchgear used to protect high voltage circuits for a whole city.

Circuit breakers have some features in common despite those substantial details that vary depending on current rating, voltage class and different types. Under low voltage conditions, they can work within the breaker enclosure, but for large current circumstances, pilot devices are required for discovering the fault current and operating the mechanism. Some high voltage circuit breakers are equiped with protection relays, transformers, and an internal power source themselves. Once detected a fault, contacts within the device would open and interrupt the circuit. Small circuit breakers may be operated by hand while larger units automatically.

The contacts carry the load current without excessive heating, and withstand the heat when the circuit breaker is working. Copper or copper alloys, silver alloys, and other materials are made for the contacts whose lifespan is limited by the erosion. When the contacts are worn, the miniature and molded case breakers are usually discarded, while power and high voltage ones often have back-up contacts.

During the interruption, an arc is produced. To make sure the gap between the contacts can bear the voltage the arc must be extinguished. This could be done by different techniques, such as lengthening of the arc, intensive cooling, division into partial arcs, zero point quenching, and connecting capacitors in parallel with contacts in DC circuits. Once the process of detecting has finished, the contacts must close to restore power for the next interruption.

Nowadays there are a lot of second-hand circuit breakers available in the market. They provide cheaper price and exactly same quality as the brand new ones thus it’s getting more and more popularity. It is worth notice that the places to buy these kinds of circuit breakers should be stores known for good quality products. You can feel relieved only by this or you can’t stop worrying about the safety of the product for a long time. The related integrated circuit is LA1810.

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