Regenerative Braking Efficiency Enhancement Using Pole-Changing Induction Motor

Permanent magnet (PM) motors are predominantly being used in electric vehicles (EVs) due to their compact size and higher efficiency. However, the performance of such motors degrades when they are operated in field-weakening mode. Therefore, it is necessary to look for alternatives. Compared to traditional induction motor drives, multiphase induction motors have better fault-tolerant capability and high torque density. Such motors can also achieve pole reconfiguration and, therefore, can operate over an extended torque and speed range. This work combines the method of pole changing with overfluxing along with maximum torque per (MTPA) and loss minimization to extend the constant power range and achieve greater energy efficiency in a multiphase induction motor drive system. A criterion to select the operating pole configuration has also been dealt with. An analytical study on improvement in energy efficiency using a combination of overfluxing and pole changing has been reported. Mathematical modeling of the overall system (considering the effects of saturation and core loss) has been done in MATLAB/Simulink and the improvement in regenerative braking efficiency has been tested. A laboratory test setup has been developed using a 5-hp six-winding induction motor and the results have been reported.