Multi-objective tradeoffs in the design optimization of a brushless permanent magnet machine with fractional-slot concentrated windings

In this paper, a robust parametric model of a brushless (BL) permanent magnet (PM) machine with fractional-slot concentrated windings (FSCW), which was developed for automated design optimization is presented. A computationally efficient-finite element analysis (CE-FEA) method was employed to estimate the dq-axes inductances, the induced voltage and torque ripple waveforms, and losses of the machine. A method for minimum effort calculation of the torque angle corresponding to the maximum torque per ampere (MTPA) load condition was developed. A differential evolution (DE) algorithm was implemented for the global design optimization with two concurrent objectives of minimum losses and minimum material cost. An engineering decision process based on the Pareto-optimal front for 3,500 candidate designs is presented together with discussions on the tradeoffs between cost and performance. One optimal design was finally selected, prototyped and tested.