What type of current does a synchronous motor require for operation?

A synchronous motor operates with alternating current (AC) supplied to the stator windings, which creates a rotating magnetic field. However, for the rotor of a synchronous motor, direct current (DC) is required. This DC is used to create a magnetic field in the rotor that is essential for synchronizing with the rotating magnetic field generated by the stator.

This synchronization is critical for the operation of the motor, as the rotor must maintain the same rotational speed as the stator's magnetic field. Thus, while the stator receives AC to facilitate this process, the rotor is energized by DC to ensure proper operation.

In this context, the correct identification of the need for DC on the rotor clarifies the unique requirements of synchronous motor operation, distinguishing it from other types of motors that may not require any DC or may use single or three-phase AC exclusively.