Contacts the contact surface of oxide layer or the role of the arc

If it is silver or silver alloy contacts, contacts the contact surface of oxide layer formed under the arc or minor burns and black, generally does not affect the work, use alcohol and gasoline or carbon mcb circuit breaker solution scrub. Even if the contact surface is uneven burned, only four weeks with a fine file splashing beads or burr removal, do not file repair too much, so as not to affect the contact life.
For copper contacts, if burned to a lesser extent, just with a fine file to smooth uneven for repair can be, but not electric meter fine emery cloth to avoid Electric transformer the quartz sand to stay in, but can not keep a good contact; If severe burns, the contact surface is low, it must be replaced with new contacts. Moving parts have jamming phenomenon can be disassembled for maintenance.