The synchronous motor will not start as soon as it is connected to the mains, but it will vibrate. When a three-phase two-pole synchronous motor is fed from a 380V / 60Hz three-phase mains, the stator currents will produce a rotating magnetic field that will rotate at 3600rpm. This field rotates so fast that before the rotor starts rotating, the torque sense developed by the rotor will already reverse the direction.


The synchronous electric motor can initiate rotational motion in two ways, either using a variable frequency power supply or as a single phase induction motor. The motor starts at a small frequency, so that the rotor can follow the rotating magnetic field.

The rotor of the synchronous machine rotates at a steady speed in steady state, with protruding type poles and this is the main characteristic for these machines. The rotating magnetic field, as a result of the interaction between the magneto-motive forces due to the three-phase sine-wave alternating currents, will rotate at the same speed as the rotor. The rotational speed of the rotor and rotating magnetic field is called synchronous speed.