Electric efficiency on the fast lane

Electric Efficiency on the Fast Lane

Min Reading Time

Shorter charging times – with ZF's 800-volt drive system. At the same time, the silicon carbide power electronics used enables electric vehicles to drive longer distances.

Kathrin Wildemann,

Kathrin Wildemann has been a part of the permanent Copy Team at ZF since 2016. In her online and offline articles, she likes to cover electromobility and other topics that involve sustainability.

Not so long ago, an intercity trip with an electric car resulted in an ordeal, even though the route was meticulously planned. After all, once the electric vehicle had arrived at one of the rare charging stations after a good 100 kilometers with an almost empty battery, drivers and passengers were able to use the following imposed break of at least one hour for an extensive lunch or dinner. Meanwhile, many things have taken a turn for the better: There are not only more and faster charging stations, but also the range of modern electric cars has increased significantly. Despite the progress in the charging infrastructure and electric mileage, many people are still skeptical towards electric drives. No wonder that many automotive manufacturers and their suppliers are focusing on the question of how to cut the charging time of electric vehicles to the duration of a coffee break.

Voltage up, charging times down

Physically, the answer is simple. Faster charging means that more power is fed into the battery in the same amount of time. However, stronger currents entail more heat, which requires thicker cables and more complex cooling systems. If manufacturers want to avoid this additional effort, they have to tackle the voltage of the drive system. The higher the voltage, the more current the vehicle battery can pick up. 400-volt architectures are the current standard for electric cars. In the premium segment in particular, more and more manufacturers are using 800-volt systems, though. The simple reason: With this drive voltage, the charging time is reduced to an average of about 10 minutes per 100 kilometers range. At the same time, there is an increase in the peak performance of electric drives – an additional advantage for sporty electric vehicles.

Three important advantages of power electronics with silicon carbide.

From Formula E to volume production

ZF is at the forefront of 800-volt technology. As a pioneer in electromobility, the technology company promises to supply electric drive solutions for all kinds of vehicles. Knowledge of the individual electric driveline components and how to integrate these individual components into an optimally configured, powerful and efficient overall system is correspondingly broad. ZF's 800-volt drive has its origin in motorsports. For the current Formula E racing series' 2020/2021 season, ZF race engineers have developed a high-performance driveline on an 800-volt basis for technology partner Mahindra Racing. Particularly efficient silicon carbide power electronics is part of the drive package. "We were able to build on the experience from Formula E for our high-voltage passenger car drive. Here, we use synergies with our established 400-volt products," says Weichen Ye. ZF's development engineer in Shanghai is an 800-volt technology expert. The meanwhile developed system appears to perfectly meet the market requirements. "We are currently preparing our first volume production start. Starting next year, a European and a Chinese automotive manufacturer will equip several of their premium models with our complete high-voltage driveline," says Ye with delight.

"For our 800-volt drive, we were able to build on our experience from Formula E."

Weichen Ye, development engineer at ZF in Shanghai

New semiconductors from power electronics for longer ranges

Silicon carbide power electronics plays a decisive role in the efficiency of 800-volt architectures. While the higher system voltage reduces the charging times, the new semiconductor material contributes to the longer range of electric vehicles. The physical properties of silicon carbide enable chips to be designed ten times thinner than classical silicon chips. This means that less power is lost when passing through the power electronics. Silicon carbide inverters also have lower turn-on losses, which has a positive effect regarding the increased switching frequencies of the 800-volt technology. "Compared to the previously common silicon inverters, silicon carbide chips are significantly more efficient while offering the same performance, especially in high-voltage drives. This enables our silicon carbide power electronics to increase the range by up to seven percent," explains Dr. Stefan Hain. He is responsible for semiconductor development in ZF's Electrified Powertrain Technology Division. The module convinces both as part of the high-voltage driveline and as an individual component.

95 %

is the level of efficiency achieved by battery-electric vehicles with silicon carbide power electronics from ZF in the WLTP cycle.