Demagnetization Analysis of a Split-Tooth Concentrated-Winding Vernier Machine using Halbach-array-based Ferrite Magnets

For home appliance industry, since cost and space are the two main concerns, high-torque-density low-speed direct drive solutions are always what people look for. A new type of split-tooth concentrated winding Vernier motor that uses consequent-pole Halbach-array-based ferrite magnets and additional stator magnets between the stator split teeth is proposed in a preliminary study that shows a promising increase in the torque density. However, due to the use of low-coercivity ferrite magnets, the side magnets of the Halbach assembly are prone to suffer from demagnetization problems, which significantly reduces its performance. In this paper, the demagnetization of this new motor topology is analyzed in detail. First, the demagnetization under no load and full load conditions is analyzed. Then, in order to understand the mechanism of demagnetization, the assembly process of the rotor magnets is simulated. An equivalent model that takes into account the demagnetization is then proposed. In order to validate the proposed model, the static field and torque constant of the prototyped motor are measured and compared between the ideal model and proposed model. Finally, the effect of the aspect ratio of the rotor magnets on the demagnetization performance is discussed.