Centrifugal Switch

The split-phase and capacitor motors use a centrifugal switch to switch out the staring winding when a sufficient speed has been reached (usually 75%)


Centrifugal switches usually have a pair of normally closed contacts that are opened when the rotor speed exceeds a given value


One of the most common centrifugal switches used a pair of weights


Normally closed contacts

In the arrangement shown above(A ball type switch), the spring holds the contacts block in touch with the contacts to the starter winding so that the circuit is closed for starting. As the motor speed up, the ball weights are thrown outward and when they are going fast enough they overcome the spring tension and pull back the contact block- opening the starting winding. It remains open as long as the motor is operating