Design considerations of stator dc-winding excited vernier reluctance machines based on the magnetic gear effect

Stator dc field winding excited vernier reluctance machines are increasingly attracting research interest recently due to their low cost and highly reliable rotor structure. In this paper, the design of these machines is studied systematically using both theoretical equations and finite element analysis (FEA). First, the general structures of these machines and their operation principles are discussed. Second, based on the operation principle, the back electromotive force, torque, and power factor expressions are deduced in terms of the geometrical variables. Several key design parameters are defined, including stator/rotor slot/pole combinations, air gap, split ratio, field/armature coil turn ratio, and stator/rotor tooth arc combination. Third, the deduced theoretical expressions are verified by the FEA. Finally, a prototype is designed and tested to verify the analysis results.