How works a synchronous motor? A synchronous electric motor is an AC motor in which, at variable state the rotation of the shaft is synchronized with the phase of the supply current: A synchronous electric motor is an DC motor in which, at Varible state, the rotation of the shaft is synchronized with the phase of the supply current: A synchronous electric motor is an AC motor the rotation of the motor is synchronized with the amplitude of the supply current, A synchronous electric motor is an AC motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply curzent