Sunday, July 8, 2012

What is a circuit breaker and how does it function?



 
A circuit breaker is an overcurrent protection device. It opens and closes a circuit automatically on a predetermined overcurrent. Subsequently, the circuit closes automatically or manually.


A circuit breaker is an overcurrent protection device. It opens and closes a circuit automatically at a predetermined overcurrent. When the circuit breaker is applied correctly within its rating, opening and closing the circuit breaker does not damage it. It is easy to reactivate the circuit breaker immediately after a overload has occurred. The circuit breaker is simply reset after the fault is corrected.

Different types of circuit breakers
We distinguish between two kinds of circuit breakers:
Thermal and magnetic circuit breakers.


Thermal circuit breakers
Thermal circuit breakers are the most reliable and cost effective type of protection device that exists and are well-suited for motors. They can withstand high-level current waves, which arise from motor starts and they protect the motor against failure e.g. locked rotor.

Magnetic circuit breakers
Magnetic circuit breakers are precise, reliable and cost-effective. The magnetic circuit breaker is stable temperature-wise, meaning that it is rarely affected by changes in the ambient temperature.
Compared to thermal circuit breakers, magnetic circuit breakers offer a more precise trip time. The illustration on your right-hand side shows the characteristics of the two types of circuit breakers.


Circuit breaker rating

Circuit breakers are rated according to the level of fault current they interrupt. So, when you select a circuit breaker, always choose one that can sustain the largest potential short-circuit current, which is likely to occur in the application.


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