The contact resistance of the circuit breaker mainly depends on the contact resistance between the static and dynamic contacts of the circuit breaker. The contact resistance is in turn composed of a shrink resistance and a surface resistance.
(l) Shrinkage resistance. Because the two conductors are in contact with each other, the surface is not absolutely smooth and flat, so that the current in the conductor is severely shrunk at the contact, the actual contact area is reduced, and the resistance is increased, and the contact resistance caused by this is the shrinkage resistance.
(2) Surface resistance. The contact surface of each conductor may have a film due to various reasons such as oxidation and vulcanization, and the film increases the electric resistance of the contact transition region, and the contact resistance is referred to as surface resistance (or film resistance).