Abstract: In a permanent magnet motor consisting of a rotor 1, which is supported on a rotating shaft 2 and has twelve permanent magnets 3 arranged at fixed intervals in the circumferential direction in the peripheral edge portion thereof, and a stator 4, which is disposed around the rotor 1 with a gap being provided with respect to the rotor 1 and has nine magnetic poles 4a, each having a coil wound thereon, arranged at fixed intervals in the circumferential direction so as to face towards the outer peripheral surface of the rotor 1, a value obtained by dividing the radius of the rotor 1 by the radius of curvature of a permanent magnet surface facing towards the stator is set at a value such as to decrease cogging torque.

Abstract: In a permanent magnet motor consisting of a rotor 1, which is supported on a rotating shaft 2 and has twelve permanent magnets 3 arranged at fixed intervals in the circumferential direction in the peripheral edge portion thereof, and a stator 4, which is disposed around the rotor 1 with a gap being provided with respect to the rotor 1 and has nine magnetic poles 4a, each having a coil wound thereon, arranged at fixed intervals in the circumferential direction so as to face towards the outer peripheral surface of the rotor 1, a value obtained by dividing the radius of the rotor 1 by the radius of curvature of a permanent magnet surface facing towards the stator is set at a value such as to decrease cogging torque.

Abstract: A micro-step drive system of a five-phase stepping motor is disclosed. When Io is a constant, a unit time interval is 1, a remainder obtained by a time variable divided by 10 is t and an arbitrary constant is .alpha. (0.ltoreq..alpha.<10), each of five-phase windings for a salient-pole corresponding to a k-th phase (k=0, 1, 2, 3 and 4) is supplied with a current I.sub.k. This winding current is obtained by pulse width modulating an output of a constant current converter by an output signal of a pulse width modulation pattern generator and supplying the modulated current to each of the windings as an output of an inverter. A power circuit of the inverter is simplified greatly.