ZF presents EVbeat concept vehicle with prototype of new 800-volt electric drive; compact, lightweight and efficient
At its Global Technology Day in Friedrichshafen, ZF presented the electric concept vehicle EVbeat, which is designed for maximum compactness, low weight, and maximum efficiency in real operation. In this ZF electric vehicle, the components of an e-driveline have been optimized and combined into a holistic system. These include the 74 kg lightweight and ultra-compact driveline with a torque density of 70 N·m/kg, holistic thermal management and cloud-networked driveline software.
EVbeat concept vehicle
At cold temperatures around freezing point, the range in real-world operation increases by up to a third compared with current technology.
The ZF EVbeat concept vehicle is based on a Porsche Taycan and takes leading series technology from ZF and other market players as a benchmark.
EVSys800 e-drive. The EVSys800 used in the concept is a modular 800-volt drive and consists of SiC power electronics, the electric motor and a reduction gearbox. Despite its extremely compact design and light weight, the EVbeat does not skimp on performance. The concept vehicle has a maximum torque of 5200 N·m available on the rear axle—and this with a uniquely high torque density for road-legal passenger cars with of 70 N·m per kilogram. The continuous and peak power of the electric motor is 206 and 275 kilowatts, respectively—ZF thus achieves continuous power of around 75% of the peak power.
In terms of dimensions, the drive saves 50 millimeters in width thanks to the compact reduction gearbox and the ZF-patented Braided Winding technology of the electric motor, thus enabling space-saving, coaxial installation on the drive axle.
E-Motor Stator with new braided winding.
With a total weight of 74 kilograms, the EVSys800, normalized to the same output as the latest ZF 800-volt series drive, is about 40 kilograms or 30% lighter and thus contributes significantly to the weight savings of the concept vehicle.
Essential for this is the electric motor with a new cooling concept and a new winding technology. For cooling, ZF allows oil to flow directly around the copper rods exactly at the point where most heat is generated during operation. Such highly efficient cooling significantly increases performance with the same weight and installation space.
In addition, the use of heavy rare earths can be dispensed with, and the electric motor can be produced more sustainably. The ‘Braided Winding’ technology developed and patented by ZF, is a further development of the wave winding and enables a total of 10% less installation space. The winding head alone is up to 50% smaller than with conventional approaches. This saves around 10% copper.
The inverter of the electric drive has been fundamentally redesigned and all essential components have been fundamentally revised. Significant improvements were achieved in each of the areas of electromagnetic compatibility, power modules and capacitors in terms of installation space, weight and sustainability.
Inverter with SIC technology
A new, coaxial reduction gearbox transmits the drive forces of the electric motor via two planetary gear sets. They not only generate the desired final drive ratio, but also perform the fully integrated differential function.
Coaxial reduction gear
Compared with conventional offset concepts, in which the input and output shafts are not on the same axis, the coaxial solution reduces weight and installation space requirements without compromising on efficiency, noise and vibration. In combination with Braided Winding technology, this drive can be made significantly shorter, allowing installation in almost any vehicle installation space.
Thermal management. The temperature control of a vehicle can account for a significant proportion of its energy requirements in winter, which can be between three and six kilowatts, especially when heating up. Pleasant coolness in summer and warmth in winter are major comfort factors for the occupants. The right temperature is also an essential factor for the performance of the electric motor, the power electronics and the battery.
The first central thermal management system (TherMaS) developed by ZF for electric vehicles is integrated into the EVbeat concept vehicle. TherMaS uses a central unit and intelligent software to control all thermal processes for the driveline and passenger compartment. The new design significantly reduces space requirements and weight compared to previous approaches for cooling and heating e-cars. A propane-based 800-volt heat pump also requires significantly less energy. Because it is compact and simple in design, it can be easily integrated into vehicles.
The TherMaS concept has three designated circuits for the first time: At the center is the very small refrigerant circuit. This is pre-filled and hermetically sealed and is therefore maintenance-free. In addition, the concept has no interfaces to other vehicle areas such as the interior. ZF uses the fluorine-free, natural refrigerant propane.
Although only half the previous refrigerant is used, the cooling capacity increases by a factor of two compared with refrigerants commonly used today. If required, the central refrigerant circuit serves two separately controllable cooling circuits in which frost-protected water flows as usual: The first is designed for the comparatively high temperatures of the electric motor, while the second regulates the temperature of the power and charging electronics. The control software regulates the cooling capacity.
Due to this overall thermal management, the range of the EVbeat increases by up to a third in demanding winter operation. The significantly better cooling performance makes the higher continuous output of the e-machine possible.
Powertrain software: efficiently network vehicle drive and cloud. The properties of the hardware systems lay an important foundation for the sustainable operation of the vehicle; their optimum orchestration is achieved via the software. ZF has developed its own powertrain software that networks all vehicle systems with each other and establishes the connection to the ZF cloud.
Because the efficiency of an electric motor depends on its thermal operating points, it is important to keep them in the optimum range at all times: At low speeds and high torque requirements, the optimum thermal operating point is very low, while at high speeds with low torque requirements, high temperatures are not a problem. However, the thermal conditions cannot be established at short notice. ZF’s driveline software can anticipate the optimum operating points from the individual driving profiles and prepare the system accordingly.
It learns the behavior of drivers and can anticipate the probability of individual driving profiles through an AI-based cloud service. For example, air conditioning and system cooling are reduced when short distances are detected.
On this basis, the assistance system can also give drivers direct advice on how to use the electric vehicle efficiently. For example, efficient acceleration and deceleration as well as an optimized maximum speed are displayed. This is particularly valuable when it comes to calculating an accurate and practical range before the journey.