One end of each of phase conductors wound around a stator core in a wave winding arrangement is connected to a positive electrode terminal of a DC power supply through a first positive electrode side switch and is connected to a negative electrode terminal of the DC power supply through a second negative electrode side switch. The other end of the phase conductor is connected to the negative electrode terminal of the DC power supply through a first negative electrode side switch and is connected to the positive electrode terminal of the DC power supply through a second positive electrode side switch. The first positive electrode side switch, the second negative electrode side switch, the first negative electrode side switch, and the second positive electrode side switch are controlled by a controller, whereby amplitude and phase of current passing through each of the phase conductors are individually controlled.