Fuses are parts intended to protect against overcurrent from mains circuits, disconnecting the motor from the mains in the event of a short circuit, it has a thermal element that fuses when it travels through a current of value higher than the design. The function of the fuses is merely to open the circuit. The circuit breakers have an advantage over the fuses which is the ability to interrupt the current in the three phases concomitantly, while in the fuses there is the possibility of interruption in only one phase resulting in the operation of the electric motor in only two phases. Another advantage of circuit breakers is overload protection. The high cost and the lower speed of short circuit operation are the drawbacks of the circuit breakers in relation to the fuses.
Circuit breakers are electromechanical switching and protection devices that can conduct and terminate currents under normal conditions of a circuit or for a set time and interrupt short-circuit currents. The circuit breakers can be open, power or molded case. The openings are usually three-pole, whereas in a shaped box they can be three-pole, bipolar or unipolar. The most commonly used circuit breakers have electromagnetic tripping for short-circuit protection and thermal tripping for overload protection.