One possibility is that the contactor contact is stuck by welding, which causes the contactor to contact for a long time; Another possibility is that the mechanical part of the contactor is stuck, leading to failure. That's residual magnetism. Take off the contactor for short-circuit discharge, and two-phase short-circuit discharge static electricity. Then the static and moving contacts rust and stick. Clean the rusty material of the contact with emery cloth to white, then slightly adjust the contact head, and measure the release gap with a feeler gauge to be about 0.2. Or a little higher, it is best to use a feeler gauge to measure the most scientific. Then restore the effect of reloading and retrying, and release the energy of the moving and static contacts during power transmission or power failure, and it is appropriate to release it normally.

Contactor refers to an electrical appliance that uses current to flow through a coil to generate a magnetic field and close the contacts to control the load in industrial electricity. It consists of electromagnetic system, contact system and arc extinguishing device.