Reduction of rotor losses in multi layer interior permanent magnet synchronous motors by introducing novel topology of rotor flux barriers

A novel topology of flux barriers in multi-layer interior permanent magnet motors is proposed in order to reduce the rotor losses including magnet eddy-current loss for the purpose of preventing thermal demagnetization of permanent magnets. First, the mechanism of rotor-loss generation is investigated by using three-dimensional finite element analysis that considers inverter carrier. The electromagnetic field is decomposed into time-harmonic components in order to understand the main factors that cause the rotor losses. From the observations, a novel topology of rotor flux barriers, which is jointed between poles, is invented. Finally, prototype motors are manufactured in order to confirm the validity of the calculation. From both results of the experiments and the calculations, it is revealed that the rotor loss of the proposed motor is significantly reduced, whereas the decrease in the peak torque is only a few percent, as compared with the conventional multi-layer motors.