The SM8 series plastic-enclosed circuit breakers (hereinafter referred to as "breakers") are suitable for AC 50Hz, rated insulation voltage 1000V (Model 63 is 800V), rated working voltage up to 690V, and rated working current ranging from 10A to 630A in distribution network circuits. They are used for distributing electrical energy and protecting circuits and power supply equipment against overloads, short circuits, under-voltage, and other fault damages. Additionally, they can serve as infrequent start and overload, short circuit, and under-voltage protection for motors.