Numerical evaluation of permanent magnet-assisted synchronous reluctance rotor topologies using a simplified magnetostatic model

Permanent magnet (PM)-assisted synchronous reluctance rotor topologies are investigated by a simplified magnetostatic finite element method (FEM) model. In this model, the slotted stator structure of an original 11-kW standard cage induction motor is replaced by an air-gap winding and an iron yoke to avoid time-consuming transient numerical simulations. The rotor consists of three rectangular shaped ferrite magnets and field line-shaped rotor flux barriers. A rotor parametrization is shown that enables the use of optimization methods. The simplified model allows then to analyze the electromagnetic torque, the internal power factor, and the PM demagnetization. Thus, different rotor variants are compared using a multi-objective (electromagnetic torque and internal power factor) genetic optimization algorithm. The number of rotor variables (height, width, and radial position of each PM) can be reduced with low impact on these objectives. The electromagnetic torque ripple is also taken into account for the final rotor variant by using a slotted stator model