What type of power supply is required for the rotor of a synchronous motor?

The rotor of a synchronous motor requires a direct current (DC) power supply. This is because the rotor is typically equipped with field windings that create a magnetic field when energized by DC. The presence of this magnetic field is essential for the synchronous motor to operate effectively, as it interacts with the rotating magnetic field produced by the stator, enabling the rotor to synchronize its speed with the frequency of the AC supply feeding the stator.

In the case of synchronous motors, the use of DC for the rotor provides continuity in the magnetic field during operation, which is necessary for maintaining synchronism with the AC supply. Without this, the rotor would not be able to lock in with the stator field, leading to inefficient operation.

While AC supplies, battery supplies, and solar power supplies serve various purposes in electrical systems, they do not fulfill the specific requirement of providing a magnetic field for the rotor in synchronous motors. Thus, a DC power supply is the correct and necessary choice for this application.