| PhD Viva

Name of the Speaker: Mr. Kunal Layek (EE19D411)
Guide: Dr. Kamlesh Hatua
Online meeting link: https://meet.google.com/ypc-ctss-eze
Date/Time: 14th March 2025 (Friday), 11:00 AM
Title: Wide Speed Range Operation of Multiphase Permanent Magnet-Based Synchronous Motor Drives For Electric Vehicles

Abstract :

Interior Permanent Magnet Synchronous Motors (IPMSMs) have gained significant traction as propulsion systems for Electric Vehicles (EVs) due to their high torque density, power density, and efficiency. However, ensuring reliability and fault tolerance remains a key aspect in EV applications, leading to the growing popularity of multi-phase Permanent Magnet Synchronous Motors (PMSMs). While multi-phase PMSMs offer several advantages well-suited to EVs, their speed range remains a concern. At high speeds, a large back-EMF is induced at the winding terminals, necessitating a higher input voltage for motor operation. In this thesis, different multiphase motor topologies are discussed which can extend the speed range of EVs while focusing on reliability. These include modified Field Weakening (FW) techniques and different winding reconfiguration techniques, as explained briefly below. Traditionally, Field Weakening (FW) has been employed to extend the speed range, however the performance of multiphase PMSMs employing FW may get restricted due to parameter mismatches between the winding phases. In this thesis, a control system is discussed for Dual Three Phase IPMSMs, which can minimize the effect of these non-idealities. A fault-tolerant algorithm is also devised for this topology. While FW can extend the speed range, at high speeds, the efficiency can be compromised. A more recent solution involves winding change-over techniques, which enhance both the speed range and high-speed efficiency. This thesis explores three such winding change-over techniques, each distinguished by its winding configuration and application. Among these, a modified tapped winding IPMSM topology is proposed for medium-duty delivery trucks operating in city traffic. This topology effectively reduces the power rating of power electronic converters by 10% compared to FW-based methods while improving high-speed efficiency by 30% in similar applications. Additionally, a Split-Tapped IPMSM topology is designed for vehicles that require a three-speed mechanical transmission. This topology uses bidirectional switches to emulate the functionality of a mechanical gear, enhancing overall drive efficiency and enabling high-speed operation. Furthermore, it has the potential to reduce the DC bus (battery) voltage requirement by up to 26% compared to conventional tapped winding IPMSMs. Finally, a Dual Three-Phase PM-assisted Synchronous Reluctance Motor (DTP PMaSynRM) is introduced, which provides a two-speed torque characteristic without requiring additional switching components. A detailed modeling and control strategy for this novel motor topology is proposed. In this viva, these concepts will be discussed, and relevant results will be presented to validate the applicability of these advanced motor topologies in EV applications.