The electric vehicle market continues to expand rapidly, with advances in battery technologies and charging infrastructure making EVs an attractive choice for a growing number of consumers in the US and across the world. While EVs allow vehicles to be powered from domestic energy sources and reduce reliance on foreign oil imports, manufacturers remain heavily dependent on a small number of non-domestic raw materials to create the permanent magnets needed for conventional EV motor drives. Price volatility, supply chain constraints, and geopolitical pressures make the ongoing reliance on permanent magnet EV motors unsustainable.  

Variable pole induction motors are of great interest for use in electric vehicles due to their increased efficiency compared to fixed pole induction motors and their lack of reliance on the scarce and geopolitically strained resources needed for permanent magnet motors. Consumers have been less than enamored with the performance of early variable-pole induction machines, however, as these models suffered from rough torque bumps that were felt by drivers during vehicle operation. Professor Arijit Banerjee and collaborators at the University of Illinois have developed two approaches to address this issue. The first employs a "bumpless" electronic pole changing method to minimize torque bump to less than 5% while achieving transition times under 200 ms. The second uses "virtual poles" to obviate bumps and achieve continuous transition. Both approaches improve transient performance during speed changes, providing a smooth driver experience. An accomopanying optimization, control, and modulation suite further optimizes performance and thermal management, allowing motors to be designed with a smaller footprint. 

Benefits

• Reduced reliance on scarce raw materials sourced from geopolitically unstable regions        
• Increased efficiency                        
• Improved performance/driver experience

Publication

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=10050555 [2]