Investigation Into Loss Reduced Rotor Slot Structure by Analyzing Local Behaviors of Harmonic Magnetic Fluxes in Inverter-Fed Induction Motor

We analyzed the local behaviors of both time and space harmonic magnetic fluxes in this research to improve the efficiency of inverter-fed induction motors. As a result, we clarified that: the magnetic flux of time harmonics passes in parallel through rotor bars and 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 manufactured a prototype that was applied to the proposed structure of rotor slots, and measured motor losses. Consequently, although the current was increased by 2%, the total loss under inverter driven condition in induction motor was reduced by 20% with the proposed structure under the equal output power of 1.1 MW.