Tula Technology, Inc., the developer of Dynamic Skip Fire (DSF) and diesel DSF cylinder deactivation technology for combustion engines, reported at the International Vienna Motor Symposium that its product Dynamic Motor Drive (DMD) (earlier post) mitigates efficiency losses of electric motors while significantly reducing reliance on rare-earth materials.

DMD’s application to electric vehicle motors has the potential to increase range while using less energy. Electric motors equipped with rare earth magnets can exceed 90% efficiency at peak performance; however, real-world driving conditions often reduce motor efficiency to approximately 70-85%, far below the peak. The patented DMD pulse density strategy mitigates efficiency losses through improvements in control software.

Tula has simulated the DMD concept and projects efficiency improvements of 2.5% on the Worldwide Harmonized Light Vehicle Test Procedure (WLTP) cycle for an average electric vehicle. These improvements increase driving range while lowering total energy consumed.

DMD is cost-effective, software-driven and does not require hardware changes to the motor or vehicle. Additionally, DMD avoids many of the rare earth material challenges including escalating future costs, limited supply and sourcing risks.

By 2040, more than half of all passenger vehicles sold globally will be electric. Tula’s Dynamic Motor Drive technology delivers high-value efficiency improvement to the full spectrum of electrification applications. With DMD, we can take a synchronous reluctance motor with low permanent magnet content and increase its efficiency to a level nearly comparable to a full permanent magnet motor. This reduces reliance on rare earth metals, which translates to lower cost and greater supply chain security. We are very excited about our DMD results, and our team is ready to work with partners and customers to optimize motor system performance in the transportation, industrial and power generation industries.

—R. Scott Bailey, president and CEO of Tula Technology

Tula’s first product, Dynamic Skip Fire (DSF), is an advanced cylinder deactivation control strategy that has been shown to significantly reduce CO₂ emissions in gasoline engines and has been in production since 2018 with more than one million vehicles on the road.

As presented jointly with Cummins at the SAE World Congress this year, the diesel application of DSF, Diesel Dynamic Skip Fire (dDSF), was shown to reduce nitrogen oxide emissions by 74% and CO₂ emissions by 5% in a Class 8 truck operating in a low-load cycle.

Dynamic Motor Drive intermittently operates the electric motor only at the highest possible electromagnetic efficiency. When requested torque is below the torque that produces highest electromagnetic efficiency, an algorithm pulses the electric motor at conditions similar to those used to generate the higher efficiency. In the example shown, optimal efficiency is at 34% of peak torque, and requested torque is at 19% of peak torque. The controller will therefore operate at the optimal efficiency point roughly 19/34 = 56% of the time. Source: Tula

DMD uses the same pulse-density concept of DSF and applies that to electric motors and systems. In essence, in response to a requested motor torque demand, Tula’s DMD algorithms operate intermittently at the torque which has the maximum efficiency.

When torque requests are low, the magnetic field is pulsed at optimal efficiency whereas in conventional motor operation, the efficiency is low at low torque.