What is the main purpose of the centrifugal switch in a capacitor-start motor?

What is the main purpose of the centrifugal switch in a capacitor-start motor?

• A. It remains closed during run to maintain capacitor in circuit.
• B. It is closed at start up to place the capacitor in series with the Start winding which creates the phase shift needed to rotate the rotor.
• C. It opens at startup to disconnect capacitor.
• D. It adjusts motor speed by varying capacitor value.

Answer: (B)

When a capacitor-start motor begins to rotate, the start winding needs a phase-shifted current to produce the strong starting torque. The capacitor provides that shift when it’s in series with the start winding. The centrifugal switch is the device that connects the capacitor into the circuit only during starting and then disconnects it once the motor has speed up. This leaves the motor running on the main winding alone, avoiding unnecessary current through the capacitor and preventing overheating.

When a capacitor-start motor begins to rotate, the start winding needs a phase-shifted current to produce the strong starting torque. The capacitor provides that shift when it’s in series with the start winding. The centrifugal switch is the device that connects the capacitor into the circuit only during starting and then disconnects it once the motor has speed up. This leaves the motor running on the main winding alone, avoiding unnecessary current through the capacitor and preventing overheating.