Design and Modeling Analysis of a Novel Propulsion Electric Machine With Variable Magnetic Pole Topology

Magnet pattern is a solution to address the challenge of enhancing the electromagnetic performance of electric propulsion machines. In this article, a novel variable magnetic pole topology (VMPT) is proposed for electric machines. It can bring several advantages. First, it can offer a unified framework for investigating the different shape variations and magnetization direction changes of the PM. Second, it helps to increase the radial air-gap flux density, which can enhance the torque output of electric machines. Third, it can generate the magnetic shielding capability, thereby reducing the rotor mass. Additionally, to analyze the electric machine with VMPT more precisely, an improved modeling method is also proposed. It takes into account the harmonic terms which are neglected by the traditional modeling method in the slotted radial air-gap flux density. By employing the improved modeling method, the magnetic field, flux linkage, back electromotive force (EMF) and torque output analytical models are formulated. Subsequently, the corresponding numerical computations are carried out to verify the effectiveness of improved modeling method in establishing high-precision analytical models. Following that, the proposed VMPT and conventional magnet patterns are compared in terms of the magnetic field, back EMF and torque output. Another comparison is also conducted between the improved modeling method and the traditional modeling method in terms of the model precision. Afterwards, one prototype of electric machine with VMPT and three experimental test platforms are developed. The experimental investigation on the magnetic field, back EMF and torque output are conducted, which verify the effectiveness of the proposed VMPT in enhancing the electromagnetic performance of electric machines.