(1) Check whether the contact pressure of the contact is too small, adjust the contact spring pressure or replace the contact spring.
(2) Check whether the main circuit connection screws are loose and whether there is an oxide layer.
(3) Check whether the contacts of the circuit breaker are severely worn.
(4) Check whether the contacts of the circuit breaker have been burned out of metal particles by the arc, which should be scraped off and polished smooth.