After the high voltage wiring harness is connected, the interlock circuit is connected. The cover plate is assembled and the switch is closed, finally closing the interlock circuit. Whether the high-voltage wiring harness is not connected, or the cover is not covered, the high-voltage interlock circuit will be opened, and high-voltage output is not allowed, thus avoiding the risk of electric shock caused by high-voltage exposure. There are many types of interlock switches, lever type or push button type, each with advantages and disadvantages. The basic principle is that the cover plate or end cap is designed with bosses or ribs. After the cover is finished, press the switch to close the switch, so that the interlock circuit is closed, and the necessary conditions for high voltage are met.