A comparison study of modelling techniques for permanent magnet machines

In this paper, four different modelling techniques for permanent magnet (PM) machines are compared for their accuracy and computational complexity. The considered techniques are primarily based on conformal mapping and harmonic modelling. In conformal mapping, the slotted air gap is mapped into a simpler canonical shape, where the field solution is calculated and then mapped back to the original domain. In harmonic modelling, the regions of the machine cross section are represented as Fourier series and coupled with each other by means of boundary conditions. The field solution is obtained by solving the boundary value problem. In order to quantify the accuracy of the field solutions, global parameters such as cogging torque and flux linkage are computed. The effectiveness of the modelling techniques are evaluated by comparing the global parameters and the simulation time with finite element analysis (FEA) results.