Dynamic Motor Drive: Optimizing Electric Motor Controls to Improve Efficiency

Authors

M. Younkins PhD, P. Carvell BSEE, J. Fuerst BSME MBA, Tula Technology, San Jose, USA:

Year

2021

Print Info

Production/Publication ÖVK

Summary

Electrification of transportation cuts reliance on fossil fuels, mitigates climate change, and eliminates tailpipe emissions. Given that the amount and cost of energy consumed by electric vehicles will soon rival those of fossil fueled vehicles, the efficiency of electric energy usage will become as critical as that of legacy energy sources. Improving the efficiency of battery-electric vehicle powertrains is key to improving the viability of this solution. Although the peak efficiencies of electric motors equipped with rare earth magnets exceed 90%, practical drive cycles and powertrain architectures frequently operate outside of the peak efficiency speed/load region. At 10% of the maximum torque of an electric vehicle, efficiency is more commonly 70-85%. In addition, the most efficient electric motors use magnets with large content of Neodymium or Samarium, both of which are expensive and have limited sources of supply. Tula’s control architecture – called Dynamic Motor Drive (DMD®) – mitigates the light-load efficiency losses of electric motors while simultaneously reducing or eliminating the reliance on rare-earth materials. By using the DMD pulse density strategy for electric motor control, inverter losses and core losses are mitigated. At high loads, experiments have proven efficiency improvements of 2% on induction motors, with more improvements possible at lighter loaded conditions. These gains project to 2.5% efficiency improvement in the WLTP. Those improvements enable reduced battery size and increased range while lowering total energy consumed, and do not require hardware changes to the motor or vehicle. This work will detail the controls methodology used to achieve those gains, the optimization of motor design for this new control paradigm, and the experimental results of that system in use.

Number of pages

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