| PhD Viva

Name of the Speaker: Sandeep V Nair (EE15D023)
Guide: Dr. Kamalesh Hatua
Online meeting link: https://iitmadras.webex.com/iitmadras/j.php?MTID=me211dc0c12ed62f2adc67ec695a5c94f
Date/Time: September 26th, 9.00 am
Title: Design and Control of 3-phase and Dual 3-phase PMSM for Improved Performance in Electric Vehicles and Marine Propulsion

Abstract

Permanent magnet synchronous motors (PMSMs) are widely used in electric vehicles (EVs) due to their superior performance than induction machines. However, the operating speed range of these machines is restricted due to the limitations in the maximum battery voltage available in the vehicle. In this work, a dual three-phase PMSM with zero degree winding displacement (DTP0-PMSM) with six-step operation is proposed to enhance the power rating and operating speed range compared to conventional 3-phase PMSMs. Dual three-phase PMSM also ensures zero circulating current even during six-step operation, reducing the copper loss compared to commonly used split-phase PMSMs. Specific applications like military vehicles, medium/heavy-duty trucks and off-road EVs demand high starting torque, high overload capability and wide constant power operating region. A dual 3-phase PMSM with unequal turns ratio (uneq0-PMSM) is also proposed to satisfy such special requirements with minimal overrating of the converter DC bus. An added advantage of uneq0-PMSM is that the shape of torque-speed characteristics can be varied during the design by changing the winding split ratio to perfectly suit the load requirement. The proposed concepts were experimentally validated on a custom-designed and fabricated 3kW IPMSM prototype.

Methods for improving PMSM starting while employing sensorless vector control are also proposed in this work. In the first part of the work, a quick and smooth changeover of PMSM control from open-loop (I-f) starting to closed-loop sensorless vector control is achieved using a novel pulse-off starting method. In the second part, a torque controller is proposed to vary the frequency slope dynamically and consequently prevent pole slipping instability while performing the open-loop start of PMSM. Both the proposed methods are highly suitable for various applications like compressors, pumps, fans and heating ventilation and air conditioning (HVAC) systems, and also for critical applications like electric ship propulsion, and emergency heat and smoke exhaust. The proposed methods pertaining to sensorless vector control were experimentally verified on a 25kW PMSM drive.