Investigation into loss reduced rotor slot structure by analyzing local behaviors of harmonic magnetic fluxes of inverter feeding induction motor

We analyzed the local behaviors of both time and space harmonic magnetic fluxes in this research to improve the efficiency of inverter feeding induction motors. As a result, we clarified that: (1) the magnetic flux of time harmonics passes in parallel through rotor bars, and (2) the magnetic flux of space harmonics passes radially through the rotor bars from the delay side in the direction of rotation. We propose a new rotor slot structure to reduce harmonic losses by taking these results into consideration. We also fabricated a prototype that was applied to the proposed structure of rotor slots, and measured motor losses in experiments. As a result, the total loss in induction motor with the proposed structure was reduced by 20%.