Dynamic Motor Drive – A Strategy Optimizing Electric Motor Efficiency        
Zhiqian Chen, Director, DMD Program Partners,Tula Technology, Inc.

Ram Subramanian, Principal Marketing Strategist,Tula Technology, Inc.

Improving the efficiency of battery-electric vehicle powertrains is a key to transportation electrification. Although the peak efficiencies of electric motors exceed 90%, practical drive cycles and powertrain architectures frequently operate outside of the peak efficiency region. Tula Technology has developed a Dynamic Motor Drive (DMD) control strategy. It mitigates the light-load efficiency losses of electric motors by a pulse density strategy. A typical motor efficiency map for traction drive is shown in the figure. Depending on the motor speed and the output torque, the motor efficiency varies at different operating points. The peak efficiency is limited to a very small range of speeds and loads. The white line in the graph depicts optimal efficiency points at various speeds. In the proposed DMD control, the algorithm compares the requested torque with the optimal efficiency line. If it is below the line, the electric motor is operated intermittently at the highest possible electromagnetic efficiency with torque pulses. In this way, inverter losses and core losses can be reduced. This torque modulation effect is maximized with synchronous Reluctance Motors (SynRM), which simultaneously reduces or eliminates the reliance on rare-earth materials. The technology benefits applications that have significant part-load operation such as in HVAC compressors, blowers and fans, automotive and rail tractions, among others. This presentation details the optimization of motor design for automotive traction drive with the new control paradigm, the control methodology used to achieve those gains, and the experimental results of that system in use.

Zhiqian Chen joined Tula in 2020, bringing his power electronics and motor drive technologies expertise to Tula’s DMD program. He also works to identify technologies and perform market segment data analysis. Prior to Tula, he held various engineering and management positions, most recently with Rheinmetall Automotive and Lucid Motors, where he focused on the intricacies of integrating electric motors with advanced EV propulsion systems. He began his career with positions in Aisin and IMRA Europe. He received his PhD and master’s degrees in Electrical Engineering from Nagoya University, Japan, and his bachelor’s from Southeast University, China.
Ram Subramanian joined Tula in 2013, bringing a background in technical marketing and program management to Tula. He heads up market research and leads many of the creative efforts in conference participation and external messaging. Prior to Tula, Ram was at Xilinx managing the worldwide university program team and at Marvell Semiconductors where his responsibilities included automotive and consumer wireless solutions applications, marketing, and business development. He began his career at Hewlett Packard as a software engineer. He has a master’s in computer engineering from the University of Cincinnati and a bachelor’s in electrical engineering from the Indian Institute of Technology, Madras.