Design of Unskewed Interior Permanent Magnet Traction Motor with Asymmetric Flux Barriers and Shifted Magnets for Electric Vehicles

Abstract

Interior permanent magnet synchronous motors (IPMSMs) are commonly used in electric and hybrid electric vehicles. Nissan Leaf electric vehicle (EV) uses skewed-rotor IPMSM as a traction motor. This motor is considered as a benchmark in this work. Although, skewing improves the torque quality of the motor by reducing the torque ripple, it reduces the average torque and increases the motor manufacturing complexity and cost. This article proposes improvements to the benchmark motor torque quality without skewing. The proposed motor uses the same stator winding and rotor magnet topologies of the benchmark motor with the same geometric constraints and magnet volume. Modifications are applied to the placement of the magnets in the rotor and the shape of the flux barriers to achieve the performance requirements. The design procedure of the proposed unskewed design is illustrated. Moreover, the electromagnetic performance of the proposed design is investigated. The design shows competitive performance in terms of the average torque, torque ripple, cogging torque, and efficiency compared to the benchmark motor. The mechanical integrity of the design is also verified. The proposed design is found to be a suitable alternative to the benchmark traction motor with a reduced rotor weight and without skewing.

Keywords:

• asymmetric flux barriers
• electric vehicle
• finite element analysis
• IPM motor
• Nissan Leaf EV
• shifted magnets

Acknowledgments

The authors gratefully acknowledge Powersys Solutions and ANSYS for the support with JMAG and ANSYS Workbench software in this research. The authors acknowledge Dr. Tim Burress from Oak Ridge National Lab. for providing additional test data of the benchmark motor that helped us validate the simulation model.

Additional information

Funding

This research was undertaken in part, thanks to funding from the Canada Excellence Research Chairs Program, and Natural Sciences and Engineering Research Council of Canada (NSERC).

Notes on contributors

Ehab Sayed

Ehab Sayed received a B.Sc. degree in Electrical Engineering with the highest distinction from Shoubra Faculty of Engineering, Benha University, Egypt, in 2010. He worked as a teaching and research assistant at the same faculty until 2016. In 2016, he received the M.Sc. degree in Electrical Engineering, Electrical Machines and Drive Systems specialization. He joined McMaster University in 2016 to pursue a Ph.D. degree in Electrical Engineering. He has been involved in many industrial projects where he designed various types of electric machines. He received a Ph.D. degree in Electrical Engineering in 2019. He is currently a postdoctoral fellow at McMaster Automotive/Aerospace Resource Center where his research interest is the design of electric machines for automotive/aerospace applications.

Rong Yang

Rong Yang received her B.S. and M.S. degrees from Department of mechanical engineering at Xi’an Jiaotong University, China, in 2010 and 2012, respectively. She joined McMaster University in 2012 to pursue a Ph.D. degree in electric machines area and received the degree in mechanical engineering in 2016. Then, she worked as a postdoctoral fellow at McMaster Automotive Resource Center in 2017. During her time at McMaster University, she has been involved in several industrial projects where she designed different traction motors and setup the high-speed electric machine test bench. Dr. Yang is currently working as a mechanical engineer at BorgWarner Waterloo Inc. since 2018. Her interest areas are the mechanical design, electromagnetic analysis, and thermal analysis of inverters for automotive electrification applications.

Jianbin Liang

Jianbin Liang received his B.S. degree in Mechanical Engineering and M.S. degree in Vehicle Engineering from Chongqing University, China, in 2012 and 2015, respectively. He received the Ph.D. degree in Mechanical Engineering from McMaster University, Hamilton, ON, Canada in 2019. He is currently a Principal Engineer at Enedym Inc., Hamilton, ON, Canada. His research interests include the acoustic noise and vibration analysis, modeling, and reduction in addition to the design of electric machines.

Mohamed H. Bakr

Mohamed H. Bakr received a B.Sc. degree in Electronics and Communications Engineering from Cairo University, Egypt in 1992 with distinction (honors). In June 1996, he received a Master's degree in Engineering Mathematics from Cairo University. He earned the Ph.D. degree in September 2000 from the Department of Electrical and Computer Engineering, McMaster University. In November 2000, he joined the Computational Electromagnetics Research Laboratory (CERL), University of Victoria, Victoria, Canada as an NSERC Post-Doctoral Fellow. Dr. Bakr received a Premier’s Research Excellence Award (PREA) from the province of Ontario, Canada, in 2003. In January 2020, he was a recipient of a Faculty Appreciation Award from the McMaster Engineering Society (MES) for outstanding contributions to undergraduate education. His research areas of interest include optimization methods, computational electromagnetics, computer-aided design and modeling of power circuits and motors, microwave circuits, THz, photonic devices, nanotechnology, and neural network applications.

Berker Bilgin

Berker Bilgin received the Ph.D. degree in electrical engineering from Illinois Institute of Technology, Chicago, IL, USA, in 2011, and the MBA degree from DeGroote School of Business, McMaster University, Hamilton, ON, Canada, in 2018. Dr. Bilgin is an Assistant Professor with the Department of Electrical and Computer Engineering (ECE), McMaster University. He is the Co-Founder and the Vice President of Engineering of Enedym Inc., Hamilton, ON, Canada, which is a spin-off company of McMaster University. Enedym specializes in electric machines, electric motor drives (EMDs), advanced controls and software, and virtual engineering. Dr. Bilgin has authored and co- authored 93 journals and conference papers and 3 book chapters. He is the Principal Inventor/Co-Inventor of ten patents and pending patent applications. His current research interests include electric machines, switched reluctance motor (SRM) drives, acoustic noise and vibration analysis and reduction, and power electronics and EMDs.

Ali Emadi

Ali Emadi received the B.S. and M.S. degrees in electrical engineering with highest distinction from Sharif University of Technology, Tehran, Iran, in 1995 and 1997, respectively, and the Ph.D. degree in electrical engineering from Texas A&M University, College Station, TX, USA, in 2000. He is the Canada Excellence Research Chair Laureate at McMaster University in Hamilton, Ontario, Canada. Before joining McMaster University, Dr. Emadi was the Harris Perlstein Endowed Chair Professor of Engineering and Director of the Electric Power and Power Electronics Center and Grainger Laboratories at Illinois Institute of Technology in Chicago, Illinois, USA, where he established research and teaching facilities as well as courses in power electronics, motor drives, and vehicular power systems. He is the principal author/coauthor of over 500 journal and conference papers as well as several books. Dr. Emadi’s research interests are power electronics, electric machines, and transportation electrification.