PURPOSE:To obtain the rotation free of torque ripple by coating two magnets which are magnetized to the inverse polarity every 120 degrees on a rotor core and spreading the three teeth with the equal intervals of a stator at 60 degrees, then by shifting a magnetization sensitive element from the center of the teeth by 30 degrees. CONSTITUTION:The windings 11 to 13 are mounted on a stator whose teeth are spread at 60 degrees. For example, an isotropic ferrite magnet is coated on the core 8 in the radial direction with inverse polarity every 120 degrees and the magnetic material or non-magnetic material 10 which is not magnetized between the magnets or the non-magnetic material is arranged. The position transducers 14 to 16 using the Hall IC are arranged so that output levels increase when the N pole is opposed. By rotating the a rotor clockwise, the respective transducer output of the waveforms (a) to (c), magnetic flux penetrating into each stator winding, and induced voltage are obtained. By properly narrowening a gap, the waveform (b) forms a trapezoid and the waveform (c) a bipolarity rectangle. This permits the S pole to be generated between the teeth of the windings 12, 13, and 11 and the rotors by each output of the trancducers 14 to 16. By applying current to the windings 12, 13, and 11, the rotation free of torque ripple can be obtained.