A power switch tube refers to a triode that can withstand a large current, has a small leakage current, and has good saturation turn-on and turn-off characteristics under certain conditions. Its amplification performance can be ignored, and its control electrode is related to the magnitude or direction of the base current. The current passes through the collector and emitter, and the direction depends on whether it is NPN or PNP tube. Field effect transistor is generally used as electronic switch, and the control is related to polarity. Compared with the traditional contactor, thermal relay and circuit breaker system, the thyristor electronic switch, a power semiconductor device, is used to replace the traditional contact control device. Compared with the traditional contactor, thermal relay and circuit breaker system, there is no contact and movable mechanical mechanism, and there are no problems such as arc, contact wear and welding, which improves the reliability of power consumption, protection and control.