What function does the capacitor serve in a capacitor start motor?

In a capacitor start motor, the capacitor plays a crucial role in generating the necessary starting torque. When the motor is initially energized, the capacitor is connected in series with the start winding, creating a phase shift between the current in the start winding and the current in the run winding. This phase shift effectively introduces an additional magnetic field that is out of phase with the main magnetic field, which enhances the starting torque of the motor.

The greater the phase difference created by the capacitor, the more effective the start winding is at producing a powerful initial torque, enabling the motor to accelerate and reach its operational speed quickly. Once the motor reaches a certain speed, a centrifugal switch or relay typically disconnects the capacitor from the circuit, allowing the motor to operate on just the run winding, which is designed for efficient continuous operation.

This function of providing phase shift for starting torque is specific to the design of capacitor start motors, distinguishing them from other types of motors that may not utilize capacitors in the same way.