Analysis of Vernier Motors Based on the Unified Theory

Abstract

Direct drive motors have come to be used as actuators in various motion control systems, since they provide fast and smooth motion precisely. However, direct drive systems without reduction gears require the motors for high torque at low speed.
The vernier motor developed as a high torque motor at low speed has not been used because of its poor power factor and various problems.
Recently, “The low speed high torque drive system applying vernier motor torque” was developed by Dr. Ishizaki. However, the characteristics of the vernier motor are not clear yet.
Authers have found that the vernier motors are analyezed as a 3-phase reluctance motors which have the different number of salient poles from poles, and have obtained the voltage equations on γ-δ axis and the general expression of the torque. The torque expression at the steady state condition is obtained in consideration of the stator winding resistance.
The tests were performed on the trial motor. The calculated pull-out torques have agreed very well with the mesured values.
The voltage equation and the torque expression of the vernier motor are very usefull for the optimum design of the motor and the design of the motion control system.