Pole ratio effect on performance of stator DC excited vernier reluctance machines

The novel vernier reluctance machines with DC field winding in stator (DC-VRMs) have the advantages of wide speed range due to the flexible exciting field by DC winding, robust rotor structure thanks to no PMs or windings on rotor similar to doubly salient machines. In this digest, the effect of ratio of rotor poles to stator armature winding poles on the electromagnetic performance, such as back-EMF, torque and torque ripple and so on are researched based on six machines, which stator/rotor slot number are 12/7, 12/10, 12/11, 12/14, 12/16, 12/17, respectively and the corresponding pole ratio are 7/1, 10/4, 11/5, 14/4, 16/2 and 17/1, respectively . It is found that, the average torque is mainly determined by the ratio of rotor poles to stator armature winding poles in a certain region . For torque ripple, it is mainly affected by the least common multiple (LCM) of the number of stator and rotor slots . For example, 12/17 exhibits the lowest (1 .4%) while the 12/16 is largest (80%) .