Optimal Airgap Permeance Design for Magnetic Field Modulated Permanent Magnet Vernier Machine

The airgap permeance of permanent magnet vernier machine (PMVM) plays an important role in the flux modulation which produces the desired harmonic to generate torque. However, traditional airgap permeance design methods usually employ fixed tooth shape and limited design parameters which cannot maximize the desired harmonic and minimize the undesired harmonic, leading to limited torque capability. Thus, this paper proposes a novel optimal airgap permeance design concept to maximize the machine torque capability. The original fixed airgap permeance modulation tooth is decomposed into multiple independent modulation factors with increased freedom for design. Then, an efficient global optimization algorithm is employed to determine the optimal airgap permeance with the aim of maximum torque. Then, an 18s56p PMVM is designed using the proposed concept as an example, achieving 32% higher torque compared to conventional design method with fixed tooth shape. This concept is also capable to improve torque ripple and power factor by optimizing the permeance. Finally, a prototype of the machine has been manufactured and performance tests were conducted, verifying the effectiveness of the design method.