Objective In order to improve the power density of the field modulated permanent-magnet machines (FMPMs), a kind of ‘fundamental harmonic’ dual permanent-magnet-excited machine (FH-DPMEM) with split-teeth stator, stator slots and rotors containing magnetic steels is proposed. The working principles of split-tooth permanent magnet vernier machine (PMVM), FH-DPMEM and ‘tooth harmonic’ dual permanent-magnet-excited machine (TH-DPMEM) are introduced respectively. Methods Based on the finite element method(FEM), the permanent magnet flux linkage and induced electromotive force under no-load operating conditions of three types of machines, as well as the power density under different loads, were investigated. Furthermore, an analysis was conducted on various characteristics of the FH-DPMEM, including air gap magnetic flux density, inductance, static electromagnetic torque, losses, and efficiency. A dual-modulation permanent magnet wind machine with a ‘fundamental wave’ magnetic field, rated at 80 W, was designed and manufactured. Relevant experimental studies were subsequently conducted. Results The simulation and experimental results show that the proposed machine has the advantages of excellent generating performance, high power density and hard external characteristic, and is especially suitable for low-speed direct-drive(DD) system such as wind power generation.
Zhang et al. (Wed,) studied this question.