Power semiconductor devices are mainly silicon controlled rectifier (SCR), giant transistor (GTR) and later gate turn-off thyristor (GTO). They are mainly used for high-voltage transmission, as well as manufacturing medium and large-sized power supplies that change the 380V or 220V alternating current of the power grid into various direct currents, and motor speed regulating devices that control the operation of motors. These devices are almost all high-voltage devices related to the power grid.