Multi-Objective Design Optimization of a Surface-Mounted Heterogeneous-Pole Permanent-Magnet Machine

A surface-mounted permanent-magnet synchronous machine topology that utilizes an array of variable depth, mixed-grade magnet segments in each rotor pole is proposed. This heterogeneous-pole permanent magnet (HPM) configuration improves torque density through air gap flux density distribution shaping. A design model describing the operation of the HPM machine is developed for use in multi-objective optimization based design. A case study of a 1.86 kW machine with a 5:1 speed range is presented; it is shown that in terms of the loss-mass trade-off the HPM is superior to a single-magnet homogeneous pole machine for the cited specifications. A two-dimensional finite element analysis is used to validate the results of the design model. A prototype symmetric HPM machine is constructed and its measured lumped parameters are compared to those predicted by the design model. Finally, a thermal equivalent circuit (TEC) of a simplified stator and end bell assembly is constructed and calibrated using the aforementioned prototype. Then the case study is repeated based on an enhanced design model which includes the TEC in the design model