A Comprehensive Disturbing Effect Analysis of Multi-Sectional Rotor Slot Geometry for Induction Machines in Electrical Vehicles

Although the performance of an Induction Motor (IM) can be maximized for any speed by use of an inverter, there is still room to contribute by optimizing the rotor slot shape while decreasing the mechanical disturbing effects and acoustic noise. This paper focuses on the effect of different individual rotor slot shapes on the performance of an IM including overall space harmonic, vibration and acoustic effects. A number of rotor slot shapes were implemented to the rotor of a commercial IM and efficiency of all designs were maximized for constant torque region by optimization. Afterwards, operational performance including starting, breakdown and rated operations; moreover, harmonic content and torque ripple were analyzed numerically in association with the mentioned rotor slot shapes. Best performing 4 rotor slot shapes in terms of chosen operational quantities were designated. Furthermore, the determined motors were carried out to vibration and acoustic noise analysis. Superposed acoustic disturbances in terms of sound power level for different harmonic frequencies were obtained and results are given in comparison. All-in-all, this paper contributes to associating the end-to-end disturbing effects to certain rotor slot shapes. This study determines disturbance and performance criterions for choosing an appropriate motor for an IM to be used in an electric vehicle. It was shown that rotor slot shape still deserves considerable attention to increase the performance of an IM while decreasing the adverse effects of space harmonics, mechanical vibration and acoustic disturbance.