Design and Analysis of Surface-Mounted Permanent-Magnet Field-Modulation Machine for Achieving High Power Factor

Along with the establishment of general air-gap field modulation theory, a new type of field-modulation machine has attracted increasing attention. However, the low power factor always plagued its popularization. This article is to focus on the simplest structure surface-mounted permanent-magnet field-modulation (SMPMFM) machine, aiming at exploring the implementation of the high-power-factor design. The key is that the power factor calculation formula is derived parametrically; hence, the originally vague causal relationship between the structural parameters and power factor becomes clear, guided by which the initial structure design for high-power-factor achievement is determined. Meanwhile, the power factor adjustment evaluation and the electromagnetic performance comparison, with the help of finite-element analysis (FEA), are conducted to verify the validity of the proposed power factor calculation formula. Finally, a feasible high-power-factor SMPMFM prototype is fabricated, and the experimental testing is performed, which shows good agreement with the formula calculation and FEA results. Hence, the validity of the proposed analysis for achieving a high-power-factor design of field-modulation machines is verified.