Abstract: A three-phase hybrid type stepping motor includes a stator having 12 salient poles 1.sub.1, 1.sub.2, 1.sub.3, . . . , 1.sub.11, 1.sub.12. The stator salient poles having the number a of stator teeth 3 and those having the number (a+1) of stator teeth are disposed alternately and a pitch .tau..sub.s1 of the number a of stator teeth and a pitch .tau..sub.s2 of the number (a+1) of stator teeth satisfy the relation of .tau..sub.s1 .gtoreq..tau..sub.s2. A pitch angle formed by central lines of the salient poles and the stator teeth disposed in the salient poles is an equal pitch of 30 degrees and the number Z.sub.R of rotor teeth being given by Z.sub.R =12n.+-.2 or Z.sub.R =12n.+-.4 (where the numbers a and n are integers equal to or larger than 1). The three-phase stepping motor has excellent characteristics in vibration, resolution and high-speed operation as compared with a two-phase stepping motor and its driving circuit can be made simple and low-cost in manufacturing.

Abstract: A stepping motor forms the teeth of the stator so that each have a predetermined pitch in order to eliminate the detent torque. In a stepping motor in which P stator salient poles 1.sub.1, 1.sub.2, . . . 1.sub.p are disposed and, on the surface of each stator salient pole opposed to a rotor 2 whose teeth 4 are disposed at equal pitches .tau..sub.R, k stator teeth 3 are each disposed at equal pitches .tau..sub.S. The stator salient poles 1.sub.1, 1.sub.2, . . . 1.sub.p comprise n sets of poles each differing in phase. The stator teeth 3 are disposed so that their pitch .tau..sub.S =.tau..sub.R.times. {1.+-. 1/(n.times.k)}.

Abstract: With this invention, realized is the maximum torque which should be generated given a value for the outer diameter dimension of a stator in a hybrid type stepping motor. In a hybrid type stepping motor 21 composed of a rotor with a plurality of teeth provided at equal pitches on a peripheral surface and a stator having a plurality of salient poles provided so as to oppose to the peripheral surface of the rotor through an air gap, the ratio of the inside diameter Di of the stator 22 to the outer diameter Do thereof is set between 0.62 and 0.64 in the case of a two-phase stepping motor and between 0.605 and 0.625 in the case of a five-phase stepping motor in order to generate the maximum torque from the rotor 23.

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.