In what way do thermal circuit breakers react to overloads?

Thermal circuit breakers respond to overloads by utilizing a mechanism that relies on thermal buildup, which allows them to trip after a specified delay rather than instantly. This approach provides a level of protection that distinguishes thermal circuit breakers from other types of breakers, such as magnetic circuit breakers that may trip instantaneously.

In the case of thermal breakers, when an overload occurs, the increased current generates heat. This heat builds up over a period of time and is measured by the thermal sensing element within the breaker. If the overload persists, the thermal element reaches a level of temperature that causes the mechanism to trip the circuit. This time delay allows for normal current spikes that may occur in certain applications without causing unnecessary interruptions, such as those seen in motors during startup.

This understanding of thermal tripping mechanisms helps clarify why options suggesting instant tripping or locking the circuit do not apply, as those functions would not be suitable for thermal circuit breakers designed to handle temporary overloads gracefully.