A Hybrid Analytical Method for On-Load Performance Prediction of Delta-Type IPM Motors Based on Equivalent Air-Gap Function

This paper presents a hybrid analytical method for calculating the on-load magnetic field distribution(MFD) and performance predictions in delta-type interior permanent magnet (IPM) machines. Referring to the idea of the lumped magnetic equivalent circuit(MEC) method, the simplest surface-inset model is established to equivale the delta-type IPM rotor with two-layered rectangular magnets, magnetic barriers and saturated iron bridges. According to the Halbach array magnets, the magnetization of the equivalent surface-inset magnet is pertinently set to have the ability to reflect the two steps in the open circuit air gap flux density of the two-layer delta-type IPM motor. In view of the equivalence of stator and rotor magnetic fields, the relative permeability and the remanence distribution of the equivalent surface-inset magnet are obtained by the relative air gap function and MEC method. And the stator with equal width slot are also simplified according to polar coordinates. Detailed theoretical explanations of obtaining the relative permeability and remanence of the equivalent surface-inset magnet are provided. On the basis of the already obtained surface-inset subdomain model, the subdomain method is used to calculate the MFD in the air gap and predicte performances of the delta-type IPM machine. The finite-element technique (FEM) and experiment are used to confirm the analytical results under the no-load and on-load conditions. The analytical method proposed in this article is not only limited to the delta-type IPM machines but also can be applied to other multi-layered and multi-segmented IPM motors.