Maximize your electric powertrain performance

Whether considering a battery-electric powertrain or hydrogen fuel cell battery-electric powertrain, you can achieve maximum efficiency in a commercial vehicle through seamless interaction between each component and a thorough understanding of their strengths and limits. When in place, the result is a harmonized electric system with several configurations to optimize the whole system's performance.

Central drive systems and eAxles

A central drive configuration, where the electric motor is mounted to the chassis and connected to a conventional axle with a driveline, is an easy way to install an electric powertrain on a vehicle. If you are considering a central drive configuration, it is important to manage the motor’s torque during propulsion and brake regen because conventional axles are typically not designed to withstand high amounts of ‘coast loading,’ which is the type of loading seen during brake regen. In some cases, you may need to reduce the amount of brake regeneration during stops to maintain the durability of the conventional axle, which ultimately reduces overall vehicle efficiency. 

An alternative is to use an eAxle. With gearing explicitly designed to handle high motor torque and high amounts of brake regeneration, an eAxle has the motor and transmission integrated into the drive axle. This integrated unit enables the best overall vehicle efficiency while saving a lot of weight.

Auxiliary systems and inverters

Managing a vehicle’s auxiliary loads, often referred to as parasitic loads, can make or break the energy efficiency of a commercial vehicle. Auxiliary systems enable everything from pneumatic functions with compressors to passenger comforting functions with HVAC - anything not related to propulsion. All these functions draw additional power to pump, push, pull, heat, or ventilate something throughout the system. 

Their individual power draw is small, but if they aren’t in the right feedback loop with the onboard energy storage system (ESS), they drain a vehicle’s overall range. Effective management of the power distribution to auxiliary loads means you have the flexibility to prioritize some energy loads over others. For example, restricting cabin comfort and setting limits to smooth acceleration can significantly extend the range from the vehicle’s existing ESS.       

Keeping up with inverter innovation

As EV powertrain technology matures, inverters are playing a bigger role in optimizing vehicle performance and efficiency, and you can expect to see additional electrical functionality incorporated into vehicle designs.

Our ELFA™ inverters use silicon insulated-gate bipolar transistors (Si IGBTs) and have the capability to support the drive control and energy management functions required by the industry today. Though new power electronic technologies are being developed and brought into the market, Si IGBTs provide a thoroughly tested and capable solution that optimizes system efficiency, performance, durability, price, and availability.

Silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET) based inverters are likely to play a more prominent role in inverter designs in the future. SiC MOSFETs are significantly smaller than Si IGBTs and are capable of higher switching frequencies with lower energy losses. Just make sure you pair your SiC MOSFET inverter with an appropriately designed traction motor to maximize system efficiency and performance.

If you mount the inverter separately from the motor, keep the distance between the two components within six feet to minimize the likelihood of the high voltage cables "swinging" due to the high pulse frequency of the SiC MOSFETs. "Swinging" could cause unwanted electromagnetic interference with the surrounding components. Another option is to take advantage of the SiC MOSFET inverter's smaller size and mount it directly to the motor on an integrated eAxle, eliminating the need for high-voltage cables between the motor and inverter. Directly mounting the inverter can optimize system reliability and cost.

The whole picture

Knowing the interdependencies within a drive system provides advantages for developing and sourcing your vehicles' most efficient individual components. However, an independently developed motor will optimize itself at the cost of an inverter and vice versa. Considering the strengths and limitations of all mechanical and electrified components during chassis design ensures peak performance and efficiency from your powertrain for the lifetime of the vehicle.

During this transitional phase of the electrification journey, we are embracing the duality of our role as eager learners and educators and look forward to helping steer the transit sector to a more sustainable future.