Optimization and Comparison of 1 MW-Class PM Motors for Aircraft Propulsion Using Litz Wire and Hairpin Windings

Choosing the right winding technology is key to maximizing power density (PD) and efficiency in electric aircraft propulsion. This article presents a two-level optimization strategy to evaluate Litz wire and hairpin winding configurations in two 1 MW-class permanent magnet (PM) machines, each with a five-stage Halbach array and a 72-slot/12-pole configuration. The global optimization (GO) stage analyzes their impact on PD, loss distribution, and efficiency. Results show that hairpin winding increases PD by reducing active mass but suffers from higher ac copper losses. To address this, an updated motor constant (K_m) serves as a fitness function in a genetic algorithm (GA) during the local optimization (LO) stage, refining the hairpin winding and stator slot design to reduce losses and enhance efficiency. Finite element analysis (FEA) validates the performance and effectiveness of the proposed method.