Performance Improvement in a Linear Primary Permanent Magnet Vernier Machine by Modular Unit Shift Effect

This article investigates the effects of modular unit shift on the detent force and mutual-to-self-inductance ratio in the modular linear primary permanent magnet Vernier (MLPPMV) machine. First, the winding connection and slot/pole combinations for the modular design are discussed. Then, the relationship of the phase shift and modular unit spacing is given. The operation principle of the MLPPMV machine is analyzed from the perspective of the air-gap field modulation theory. Moreover, the analytical expressions of the modular unit shift and phase shift angle for the MLPPMV machine are derived. Afterward, the back EMFs, detent forces, and inductances are comparatively analyzed. The investigation reveals that the reasonable modular unit shift has significance to improve the electromagnetic performances. Furthermore, the finite-element method is adopted to evaluate. Finally, a prototype of MLPPMV machine is built. Experiments are carried out on a linear test bench, verifying the theoretical analysis.