The centrifugal switch is an electric switch that operates using the centrifugal force created from a rotating shaft of an electric induction motor. This switch is designed to activate or de-activate as a function of the rotational speed of the shaft in single-phase and split-phase induction AC motors.
In the process of starting, a single-phase appliance motor is too weak to overcome friction and inertia. The capacitor and coil boost the motor’s torque and get it started, but become a power drain once the motor is up to speed. As the motor reaches a certain speed, a mechanism in the switch responds to the centrifugal force, pulling against it. This opens the switch and breaks the electrical connection, as the motor no longer needs the boost. So once the motor comes up to its operating speed, the switch turns off the boost circuit, and the motor runs efficiently. When the motor stops, a spring pulls the switch mechanism closed again.