Which type of circuit breaker operates immediately and has no delay in tripping?

The type of circuit breaker that operates immediately and has no delay in tripping is the instantaneous-trip circuit breaker. This circuit breaker is designed to react quickly to overload conditions or short circuits. It relies on an electro-magnetic mechanism that senses the current flowing through the circuit; if the current exceeds a predetermined threshold, the breaker activates almost instantly, cutting off the electrical supply. This feature is critical for protecting sensitive equipment from damage that can occur due to sudden spikes in current.

Other types of breakers, such as thermal and time-delay circuit breakers, incorporate various forms of delay. Thermal breakers use heat to trip the circuit, which means they can take a few moments to react to an overload condition. Time-delay breakers are designed to allow for temporary surges in current—common in applications like motors—before tripping, giving the system time to stabilize. Magnetic breakers, while quicker than thermal types, may still have a slight delay when they operate based on the current levels, particularly under non-abnormal load conditions. Thus, the instantaneous-trip circuit breaker stands out for its immediate response, ensuring prompt protection for electrical circuits and equipment.