Operation and Design Principles of a PM Vernier Motor

In this paper, the back electromotive force and power equations of a permanent-magnet (PM) vernier motor are accurately derived considering an air-gap permeance function expressed in terms of practical machine dimensions. Using these equations, the nature of a PM vernier motor is analytically surveyed, and substantial information such as main geometric factors affecting torque and the maximally obtainable torque for a given current are provided, leading to a new relation for torque per air-gap volume. In addition, these equations provide a means to determine the slot and pole combinations to realize greater power density. Finally, the effects of an increased reactance are investigated in respect to machine performance with a given voltage.