Performance Analysis of Permanent Magnet Vernier Motor with Surface and Halbach Magnets

Background: Surface permanent magnet motors (SPMVM) and dual permanent magnet motors (DPMVM) have broad prospects in direct drive systems, but some problems occur with large magnetic leakage, large torque ripple and large amount of permanent magnets (PMs). Objective: In order to reduce the torque ripple and magnetic flux leakage of SPMVM and DPMVM, and improve the torque density, a dual permanent magnet vernier machine with Halbach PM array (DHPMVM) is proposed. Methods: By air gap permeance method, flux density analysis of three kinds of motors was analyzed, and the main harmonics of SPMVM and DHPMVM are investigated with structure parameters. Electromagnetic characteristics of three motors such as no-load back, electromotive force (EMF), torque, and inductance are compared and analyzed by finite element method (FEM). Results: The study found that under the same size, winding distribution, electrical load and speed conditions, DHPMVM uses Halbach PM array and consequent pole structures to reduce magnetic flux leakage and torque ripple, increase torque density, PM utilization and torque per unit PM volume. Compared with SPMVM and DPMVM, the DHPMVM proposed in this paper has better electromagnetic performance. Conclusion: The DHPMVM topology is the better choice in terms of torque density, torque ripple, and magnet usage among the investigated topologies.