Multi-Objective Optimization of a V-Shaped Interior Permanent Magnet Synchronous Motor for Electric Tractor Drives

Electric tractor traction motors require stable torque under low-speed, heavy-load operation. This study investigates a 40 kW, 3000 r/min V-shaped interior permanent magnet synchronous motor (IPMSM) and develops a rotor structure optimization procedure integrating Maxwell finite element analysis, Latin hypercube sampling, sensitivity screening, and the non-dominated sorting genetic algorithm II (NSGA-II). The magnetic bridge thickness (HRib) and permanent magnet thickness (ThickMag) were ranked highest by the linear screening and retained for the reduced two-variable refinement and set to 1.92 and 5.36 mm, respectively. The optimized design maintained the average electromagnetic torque at 119.40 N·m, while the peak-to-peak cogging torque decreased from 5.94 to 1.66 N·m and the loaded torque ripple coefficient decreased from 17.46% to 2.90%. Prototype tests yielded a peak-to-peak cogging torque of 1.85 N·m, 11.45% above the optimized finite element result. At 800 r/min and approximately 120 N·m, the measured average shaft torque, peak-to-peak torque, and ripple coefficient were 118.50 N·m, 5.83 N·m, and 4.92%, respectively. The larger experimental ripple is consistent with combined electromagnetic, control, measurement, and drivetrain effects absent from the electromagnetic model; their individual contributions are not identified by the present data, so the loaded result is interpreted only as trend-level evidence at the tested point.