What is Dynamic Torque Switching?

Dynamic Torque Switching™, also known as eDTS™ is an innovative electric propulsion technology for a range of electric vehicles (EVs). It delivers a significant improvement in power efficiency and performance, which translates into a net reduction in vehicle cost through smaller battery packs, extended range, or a combination of the two.

Effciency is Key to EVs

ePropelled’s take on efficiency is very broad and focused on getting more output from the same input, unlike other technologies. More specifically, we use energy more intelligently and economically to deliver superior performance. Most motors’ highest power efficiency is only available in a very narrow band (a small island we refer to as a “sweet spot”) on the power map. Our eDTS technology allows vehicles to operate at maximum efficiency at a much wider efficiency band (a very large island) on the power map.

ePropelled has patented the technology that allows the electric motor to provide high torque at low speeds without drawing high current from the batteries. It also provides high speeds at low torque levels without using deep field weakening and at much-reduced winding losses, thereby increasing the efficiencies throughout. This technique utilizes the motor magnets and the motor windings optimally and improves the overall drive cycle efficiency, allowing the range of the vehicle to increase by at least 15% (based on New European Driving Cycle—NEDC—simulations).

The Power Curve

Internal combustion engine (ICE) vehicles are typically limited to an operating range of 1,000 to 6,000 RPM and require complicated, expensive, and heavy multi-ratio gearboxes to produce usable power over the operation range that extends from a standstill all the way to its maximum speed. However, the result is a smooth torque curve across the full operating range.

ICE relies on gearing for a smooth power curve.

Conventional EV motors can produce a similar curve, but at the cost of efficiency. As is seen in the diagram, the peak efficiency occurs in a relatively small area—the “sweet spot” (an island) for the motor—and it tails off markedly at higher speeds.

Conventional electric motors are less efficient at high torque and high speed.

eDTS Technology Works Differently

Our eDTS technology overcomes these limitations and delivers a smooth power curve with high efficiency throughout. The different modes that it creates can provide multiple “sweet spots” that correspond to the operational needs of the vehicle, such as high torque for starting from a standstill to high efficiency at highway speeds.

The eDTS system reconfigures the motor modes using hardware and software. As a result, each mode will have different characteristics including torque profile, speed range, and constant power range. This allows for very efficient delivery of optimized performance across the power curve by minimizing the losses in the magnetic material and copper windings.

eDTS technology allows our single motor to function as if it were multiple different motors, each ideally suited to a desired “sweet spot” on the curve and each area of high-efficiency being additionally expanded. This way, each mode is optimized to deliver different performance characteristics, such as high torque when starting from a stop and a seamless change to high efficiency at higher speeds. Since these needs change quickly and frequently when driving, our sophisticated software control is an essential aspect of the system.

The magnetic field pattern and other parameters of the electric machine change, giving it the flexibility to operate optimally when controlled by the adaptive power electronics drive. The control system is designed to allow the transition between the modes to take place seamlessly to deliver optimum torque/speed/efficiency characteristics in real time.

Our eDTS technology is based on our patent for reconfigurable windings and the system comprises three main components:

  • The eDTS motor is a brushless permanent magnet synchronous machine. In this example, it is an interior permanent magnet motor (IPM motor) where the rare earth magnets are embedded in the rotor. The stator and rotor consist of laminated cores. The distributed phase windings are divided into sections and are inserted in the stator.
    The cooling of the motor is achieved and maintained by using integrated water-cooling ducts in the housing. Our expertise in magnetic engineering is manifest in the choice of active materials used and how they are implemented in the magnets, windings, and laminations. This motor design provides an ideal combination of high torque, high power density, and high efficiency.
  • The power electronics drive is paired with the motor for the best performance. It includes a high voltage inverter and a control system. Based on vehicle demand, the control system will automatically select the most efficient operation mode, which will save battery energy and increase driving range. The control system uses real-time adaptive shift maps and machine learning to control the switch matrix and the motor parameters for optimum propulsion system performance. The unit is liquid-cooled and we leverage SiCFET technology to ensure optimal efficiency.
  • The switch matrix links the many windings of the motor to the phases of the drive. Based on the input from the control system, the switch matrix connects the sections of the windings in a series, series-parallel combinations, or all in parallel. Among others, this manages the control of the induced back electromotive force (back EMF), current draw and density, and magnetic flux linkage, resulting in switching the torque, speed range, and constant power range. eDTS’s combination of motor design, material science, and software control produces a much more efficient method of electric propulsion at various torque and speed levels.

The system is highly scalable to meet the needs of a broad range of EVs:

  • The motor size can be altered, based on the continuous and peak power requirements of the vehicle.
  • The inverter is a modular design where the control board remains the same but the power stage scales with power requirement.
  • The switch matrix can be changed based on the performance requirements of the vehicle.

How eDTS Technology Improves EV Performance

David Hudson and Nabeel Shirazee present at Cenex LCV in September 2021 in this 15 minute video: