What type of capacitor is used in most start circuits of single-phase motors?

In single-phase motors, a start capacitor is specifically designed to provide an extra boost of torque during the startup phase. When a motor initially powers on, it requires a higher torque to overcome inertia and reach operational speed. The start capacitor temporarily stores electrical energy and releases it into the motor winding, enhancing the magnetic field and facilitating a higher starting torque.

This capacitor is typically connected in series with the start winding and is designed to be energized only for a short duration during startup. Once the motor reaches a certain speed, a centrifugal switch or relay typically disconnects the start capacitor from the circuit, allowing the motor to run efficiently on its main winding.

While run capacitors are also used in single-phase motors, they serve a different function by improving the motor's efficiency and running characteristics rather than providing the necessary initial torque required for starting. Other types of capacitors mentioned, such as electrolytic or bypass capacitors, are not primarily used for start circuits in single-phase motors.