How does a thermal magnetic circuit breaker operate?

A thermal magnetic circuit breaker operates by utilizing two separate mechanisms to provide overcurrent protection: the thermal element and the magnetic element. The thermal part of the breaker responds to prolonged overcurrent conditions by heating up a bimetallic strip, which bends and eventually trips the breaker when the temperature rises sufficiently. This helps protect against overload conditions that could cause damage to the circuit or connected devices.

The magnetic element functions in response to short circuits. When a sudden surge of electric current occurs, the magnetic force generated by the current flow can exceed a predetermined threshold, which causes the breaker to trip almost instantly. This dual-functioning mechanism—thermal for slow, sustained currents and magnetic for rapid surges—ensures a reliable and responsive protection strategy for electrical circuits.

This explanation clarifies why the thermal magnetic circuit breaker operates efficiently in protecting electrical systems from both overloads and short circuits.