subject: Circuit Breakers [print this page] What is a circuit breaker? What is a circuit breaker?
The job of a circuit breaker is to cut off an electrical current when the charge becomes overloaded or short-circuits. The idea is that they prevent the device or machine that is being powered from being damaged.
Like fuses, they are used widely in household devices but are also used for machinery in factories and, in some cases, can protect high voltage currents for a whole town or city's grid.
However, unlike fuses, they do not need to be changed every time an issue occurs. The user can merely flick a switch to reset the breaker and normal operation will resume.
There are various types of circuit breaker, but two of the most common and effective for businesses are called thermal and magnetic circuit breakers.
Thermal circuit breakers
Thermal circuit breakers use heat to detect whether too much electrical current is being passed through to a device.
It is made to contain a bi-metal strip which allows the electricity to pass along it. If this strip gets too hot it snaps up, breaking the current and preventing the device from being damaged.
Once the bi-metal strip has cooled it can be put back into its old position by the flick of a switch.
Magnetic circuit breakers
Magnetic circuit breakers use a magnetic actuator known as a solenoid to stop the flow of electricity.
The electricity flows through a tightly-wound magnetic coil of the solenoid and when the voltage gets too high the heat causes the solenoid's pulling force to increase. If this force gets to a certain level it releases a latch which allows the two opposing ends of a metal strip to pop apart and stop the flow.
Some circuit breakers use a combination of thermal and magnetic technology. However, in these devices, the bi-metal strip found in a thermal circuit breaker is used to trip the latch rather than snapping the metal contacts apart.
