The current flows in from the fixed contact 1, and flows out from the fixed contact 2, through the moving, fixed silver contact and the moving contact. The moving contact quickly disconnects under the action of strong electric repulsion force (Holm force and Lorentz force) to improve the breaking speed.

When the short circuit large current occur in the circuit, the gas producing parts will generate other gas under the high temperature of the arc, the air pressure in the contact unit box increases rapidly, and a high-speed air flow can be formed through the air outlet of the arc extinguishing chamber, which can effectively extinguish the arc.