Which type of winding is commonly used to create the phase shift in a split-phase motor?

In a split-phase motor, the phase shift necessary to create rotation is achieved through the use of a starting winding. This winding is strategically designed and placed to be out of phase with the main winding, creating the required phase angle to initiate the motor's rotation. The starting winding typically has a higher resistance and reactance compared to the run winding. When power is applied, the current flowing through the starting winding creates a magnetic field that is out of phase with the magnetic field generated by the run winding, thus providing the necessary start torque to kick the motor into motion.

Once the motor reaches a certain speed, a centrifugal switch or relay typically disconnects the starting winding, allowing the motor to operate solely on the run winding. This design is essential in split-phase motors to ensure efficient startup and operation. The primary function of the starting winding, therefore, is to facilitate the initial phase shift, leading to effective motor performance.

In contrast, other windings mentioned, such as synchronous windings and secondary windings, serve different purposes and are not involved in creating the phase shift in a split-phase motor scenario. The run winding is necessary for continuous operation but does not contribute to the initial phase shift needed at startup.