Multiphase induction motor drive with 1:3:9:15 speed ratios for gear free electric vehicle application

Wide variation in speed from low speed crawling to high speed cruising, maintaining constant power operation is the most desired characteristic of a drive used in electric vehicles (EV). Pole phase modulated multiphase induction motor (IM) drive is capable of extending the constant power operation over very wide range of speed with transient high torque for electric launch or hill climbing. In this paper a 45 phase squirrel cage IM drive with 1:3:9:15 speed ratio using pole phase modulation is proposed. The four speeds achieved by electrical pole changing eliminate the need of mechanical gear box which saves in weight and size of the EV. Phase number appears to be slightly large, but with the advantages such as reduction in voltage rating of the power switch and dc link supports the selection of large phase number. In addition high number of phases considerably reduces torque ripple and increases efficiency by reducing slot harmonics, operation of the proposed EVI drive for 45 phase 2 pole, 15 phase 6pole, 5 phase 18 pole and 3 phase 30 pole combinations is verified by FEA simulation using 5hp model in Ansys Maxwell (an electromagnetic package) and Simplorer (associated circuit simulator). Drive performance with pure sinusoidal voltage and two-level inverter excitation are compared. Due to the selection of high number of phases even with two-level inverter excitation, performance of the drive is not degraded.