What role does the capacitor play in a single-phase motor circuit?

The role of the capacitor in a single-phase motor circuit is to provide a leading current in the start winding. In single-phase motors, particularly split-phase and capacitor-start motors, the capacitor creates a phase shift that allows the motor to generate a rotating magnetic field. This is essential for starting the motor and ensuring it runs smoothly.

When the motor is energized, the capacitor connects in parallel to the start winding, creating an auxiliary circuit. This phase shift causes the start winding to produce a magnetic field that is out of phase with the main winding, resulting in a more balanced magnetic field. This is crucial for providing the initial torque necessary to start the motor. Once the motor reaches a certain speed, a centrifugal switch or relay disconnects the capacitor, and the motor runs on the main winding alone.

This function of the capacitor is critical to the operational efficiency of the motor and is especially important in applications where high starting torque is required.