Analytical modeling and multi-objective optimization of Halbach array permanent magnet synchronous motor

Purpose To reduce dependence on finite element software, ensure the accuracy of results and intuitively reflect the relationship between motor parameters and magnetic field, this paper aims to adopt a new technological approach for motor multi-objective optimization design. Design/methodology/approach First, this paper presents a universal analytical model for slotless Halbach array permanent magnet (PM) synchronous motor and derives the air-gap flux density and back electromotive force (back-EMF). Second, the influence of pole pairs, PM thickness, air-gap length, magnetization angle and main magnetic pole width on air-gap flux density was analyzed. The case where the air-gap flux density of an air-core motor (without a rotor iron core) is higher than that of an iron-core motor was also discussed. Third, a genetic algorithm was used to perform multi-objective optimization of the air-gap flux density and PM mass based on the analytical model. Finally, a high-lift motor prototype was manufactured, and the feasibility of the analytical modeling was verified through the back-EMF results of the prototype. Findings When the pole pairs are large enough, the influence of the PM thickness on the air-gap flux density fundamental amplitude is smaller. For the segmented Halbach array, the larger the magnetization angle is, the smaller the pole width is, and the air-gap flux density of the air-core motor is larger than that of the iron-core motor. Originality/value The analytical model is applicable to both inner and outer rotor motors, and it is simple (with one undetermined parameter) and has high accuracy. Meanwhile, based on this analytical model, multi-objective optimization analysis can be conducted quickly without relying on finite element software.