Design and Analysis of a Direct-drive Permanent Magnet Vernier Motor for Electric Drilling Applications

Direct-drive permanent magnet motors applied in downhole applications, eliminating the gear reducer, have gained rising attention for the high reliability. A permanent magnet vernier motor (PMVM) with high torque density which is potentially suitable for downhole electric drilling applications, is designed by finite element method in this paper. The design consideration of PMVM is analyzed, which is slightly different from permanent magnet synchronous motor (PMSM) due to its magnetic field modulation. Several main parameters influencing the performance are investigated, and an optimal design adopting genetic algorithm is obtained. Compared with the traditional PMSM design, the torque density of PMVM can be enhanced by about 22%.