Reduction of harmonic iron losses in interior permanent magnet motors by optimization of rotor structures

Rotor structures of interior permanent magnet motors are investigated in order to reduce harmonic iron losses at high rotational speeds under field-weakening control. First, an optimization method combined with an adaptive finite element method is applied to automatically determine the shapes of the magnets and rotor core. The optimized motor is manufactured to verify the validity of the calculation. It is clarified that the iron loss of the optimized motor is reduced to nearly half of that of the conventional motor, without a significant decrease in the maximum torque. Next, the contribution of each part of the rotor to the iron loss reduction is analyzed by the experimental design method. Finally, several types of the rotors are proposed from the viewpoints of the manufacturing cost and performance.