Abstract
In hybrid type (HB type) stepping motors, 2 phase motors have been used widely, and 4 phase or 5 phase motors have also used for a high resolution purpose. It is generally said that, the motor performance is improved as the number of phase is increased. However, increased number of phase results in the increase of stator poles, complicated manufacturing process and driving circuit accompanied by higher manufacturing cost. In case of 3 phase stepping motors, however, the number of poles less than 8 poles which are widely used in 2 phase motors can be available. Furthermore, number of driving transistors can be reduced, because number of winding terminals for power supply can be reduced to 3. From these considerations, HB type 3 phase stepping motors look possible to be an actuator superior in the point of cost-performance. In spite of such possibility, little review of 3 phase HB type stepping motors has been found.
In this paper, 3 phase HB type stepping motor is reviewed in the following points. They are, (1) It is shown that HB type 3 phase stepping motor has 2 types of construction which are different in magnetic path, and the features of both types are discussed. (2) Equations for static torque characteristics are derived, and the effects of rotor harmonic flux on the torque-angle characteristics are clarified. (3) Step response characteristics and (4) Pull-out torque characteristics are analysed for various excitation modes, and the results are compared and discussed.
