Investigation of Optimal Design of IPM Motor using Finite Elements and Optimization Technique

Abstract

The interior permanent magnet (IPM) motor has many advantages, such as high efficiency etc., and this motor is becoming widely used not only in home applications like air conditioners but also electric vehicles. Although the investigation of optimal design of IPM motors is important, the analysis of IPM motors using the finite element method and the optimization method is very rare. This is, because the IPM motor should be analyzed considering the rotation of rotor in order to obtain the torque ripple, the mesh generation at each step of rotation is troublesome. If the nonconforming mesh technique is used in the optimization problems with rotating meshes, the practical optimization considering the rotation of rotor becomes easy, because the mesh at each angle of rotation can be obtained by only combining meshes of a rotor and a stator.
In this paper, techniques for the optimal design of permanent magnet motor considering rotation are investigated. The nonconforming mesh and the optimization technique such as Rosenbrock's mthod (RBM), evolution strategy (ES) are introduced for practical design. The constraints of the minimum average torque and the maximum induced voltage are also taken into account during the optimization. The effects of the kind of objective function and the optimization method on the obtained result are discussed. It is shown that about 25% of volume of magnet and about 20% of torque ripple can be reduced by using ES.