Efficiency Improvement of Electric Motor Drives using Dynamic Motor Drive Technology
2022-01-0890
03/29/2022
- Event
- Content
- Transitioning to battery electric vehicles is the largest opportunity available to the automotive industry today. Improving the vehicle’s range and reducing the vehicle’s production cost will help expedite that transition. To achieve acceptable range, most BEVs depend on highly efficient electric motors containing rare-earth permanent magnets (PM). However, rare-earth materials have supply chain issues that have caused price volatility and increased the risk of transportation electrification. To mitigate that supply concern, Tula Technology is working to increase the efficiency of alternative designs. It has developed a novel motor control strategy called Dynamic Motor Drive (DMD®), which is particularly suitable for rare-earth-free or reduced rare-earth permanent magnet-based electric motor drives. DMD reduces the light-load losses of electric motor drives by intermittently pulsing motor torque. As practical drive cycles and powertrain architectures frequently operate at light loads, DMD can significantly reduce the energy consumption of BEVs over all drive cycles and increases the maximum range of the vehicle. Therefore, the adoption of DMD technology will improve the efficiency of rare-earth-free or reduced-rare-earth PM based traction e-motor drives, and expedite transportation electrification. This study presents the theoretical background of DMD® technology and details experimental validation results on an 8 kW three-phase synchronous reluctance motor (SynRM). Extensive finite element analysis (FEA) results are also provided which allowed early validation of the loss reduction capability using the DMD control strategy. This study also discusses motor designs and control techniques optimization using in-house and commercial software tools to allow the highest system efficiency with acceptable noise, vibration, and harshness (NVH). Furthermore, an in-depth discussion of Tula’s pulse density strategy currently in use in production gasoline vehicles details the extension of these strategies to BEV’s. Experimental results show that DMD’s pulsed torque operation successfully improves the system efficiency of prototype SynRM drive over a wide range of operating speeds. Improvements were seen in both inverter losses and iron losses. Test results indicate that DMD technology, when applied to a 150kW SynRM on Chevy Bolt BEV, can reduce the overall energy consumption by 2.5% over the Worldwide Harmonized Light Vehicle Test Procedure (WLTP) drive cycle. The test results also indicate that enabling DMD can save energy over other vehicle drive cycles as well as other applications like HVAC and fan-pumps. In conclusion, Tula’s DMD technology can successfully improve the rare-earth-free SynRM drives’ efficiency in all drive cycles with no additional hardware.
- Citation
- Islam, M., Carvell, P., Tripathi, A., Younkins, M. et al., "Efficiency Improvement of Electric Motor Drives using Dynamic Motor Drive Technology," SAE Technical Paper 2022-01-0890, 2022, .