How does a synchronous motor controller initially start the motor?

A synchronous motor controller initiates the operation of the motor by starting it as an induction motor. This is essential because synchronous motors require a specific condition to achieve synchronization with the supply frequency. At startup, the rotor is not yet synchronized with the rotating magnetic field created by the stator. By initially operating as an induction motor, the controller allows the rotor to gain speed until it approaches the synchronous speed, making it easier to achieve synchronization.

Once the motor reaches this point, the controller can employ methods such as field excitation to bring the rotor into sync with the stator's magnetic field, thus transitioning the motor into its synchronous operating mode. This process is crucial because if the motor were to attempt starting directly in synchronous mode, it could stall since the rotor would not be moving fast enough to synchronize with the stator's magnetic field.

The option suggesting synchronization with the line frequency does not capture the initial starting method, as that refers to the condition after the motor has achieved synchronous speed. Similarly, synchronizing the power factor and frequency pertains to operation metrics mid-performance rather than the start-up process itself.