Centrifugal Switch Action

A single-phase AC motor has a centrifugal switch inside its case, attached to the motor shaft. The switch is closed when the motor is off and motionless. When you turn the motor on, the switch conducts electricity to a capacitor and an extra coil winding in the motor, increasing its starting torque. As the motor's revolutions per minute increase, the switch opens, as the motor no longer needs the boost.