ZF – Most Compact E-Drive with World Champion Torque Density

The Friedrichshafen-based supplier is presenting the electric concept vehicle EVbeat, which is designed for maximum compactness, low weight, and maximum efficiency in real-world operation. The components of an electric drivetrain in the ZF electric vehicle are optimized and consolidated into a holistic system. These include the ultra-compact drive, which is 74 kilograms light with a torque density of 70 Nm/kg, an integrated thermal management system, and cloud-connected drivetrain software. At cold temperatures around the freezing point, the range in real-world operation is expected to increase by up to one-third compared to current technology.

“Sustainable mobility is the core of our corporate strategy,” explains Stephan von Schuckmann, a member of the Board of Management at ZF, who is also responsible for electrified drive systems. "Based on an already efficient series vehicle, we demonstrate the potential future E-drive components offer when combined into an even more efficient overall system."

Base Vehicle Porsche Taycan

The ZF concept vehicle EVbeat is based on a Porsche Taycan and takes leading series technology from ZF and other market players as a benchmark.

“Our goal was to make this drive as compact and light as possible while maintaining high driving dynamics and increasing the range in real-world operation,” says Dr. Otmar Scharrer, head of development for electric drive systems at ZF. "When it comes to torque density, we are at the top of the podium compared to the currently available electric drives for passenger cars. At the same time, we have placed a strong emphasis on sustainability in development."

The electric motor comes without heavy rare earth elements, and the thermal management system operates without fluorinated refrigerant. The lower number of components and the approximately one-third reduced system weight in the electric drive and thermal management contribute doubly to more sustainability – both in manufacturing and in operation.

Electric Motor: Small and Powerful

The EVSys800 is a modular 800-volt drive consisting of silicon carbide power electronics, the electric motor, and a reduction gearbox. Despite its extremely compact design and lightweight, it does not skimp on performance in the EVbeat: The concept vehicle offers a maximum torque of 5,200 Newton meters at the rear axle – with a uniquely high torque density for road-legal vehicles of 70 Newton meters per kilogram of drive weight. The continuous and peak power of the electric motor are 206 and 275 kilowatts respectively – ZF thus achieves continuous powers of around 75 percent of the peak power.

In terms of dimensions, the drive saves 50 millimeters of installation space in width thanks to the compact reduction gearbox and ZF's patented "Braided-Winding" technology of the electric motor, enabling a space-saving coaxial installation on the drive axle.

With a total weight of 74 kilograms, the EVSys800 is approximately 40 kilograms or one-third lighter, standardized to the same power as the latest ZF 800-volt series drive, thus significantly contributing to the weight savings of the concept vehicle.

Unique Winding Technique and New Cooling Concept

Central to this is the E-motor with a new cooling concept and a new winding technology. ZF uses oil to directly flow around the copper bars – precisely at the spot where most heat is generated during operation. Such highly efficient cooling significantly increases performance while maintaining the same weight and installation space. This also eliminates the need for heavy rare earth elements, allowing the E-motor to be produced more sustainably. The "Braided-Winding" technology developed and patented by ZF, an advancement of the so-called wave winding, allows for an overall space reduction of ten percent. The winding head alone becomes up to 50 percent smaller than conventional approaches, saving around ten percent copper.

New Inverter and Compact Reduction Gear

The inverter of the E-drive has been fundamentally redesigned, with all key components thoroughly revamped. Significant improvements in terms of space, weight, and sustainability have been achieved in electromagnetic compatibility, power modules, and capacitors.

A new coaxial reduction gear transmits the drive forces of the E-machine via two planetary sets. These not only generate the desired axle ratio but also serve the fully integrated differential function. Compared to common offset-concepts, where the drive and output shafts are not on the same axis, the coaxial solution reduces weight and space requirements. In combination with the "Braided-Winding" technology, this drive can be made significantly shorter, enabling installation in almost all vehicle spaces.

"With this system, we can perfectly meet our customers' main requirements: efficiency, performance, and cost," says Dr. Otmar Scharrer.