|Major elements of the new Zytek EV powertrain: inverter and power electronics (top); transmission (middle); and the air-cooled motor (right). Click to enlarge.|
UK-based Zytek Automotive is developing a third-generation electric vehicle powertrain. The unit is a clean-sheet-of-paper design intended to simplify the introduction of next-generation electric vehicles, from niche models to high-volume global programs.
The turnkey package is extremely compact and in air-cooled configuration is up to 45% lighter than today’s production EV powertrains. Even the water-cooled version, suitable for demanding drive cycles, is up to 30% lighter. Available in sizes from 25kW, the highly integrated modular system can be configured for a wide range of vehicle sizes, applications and architectures.
The steps required to move from today’s low-volume trials to tomorrow’s fully-homologated production vehicles are very substantial and must not be under estimated. Everything has to be re-evaluated, from development processes to dealer training. This new powertrain, combined with our substantial experience of EV and hybrid vehicle production programs, will take time and cost out of this activity while helping to deliver the quality, refinement and driving experience that discerning customers demand.
—Zytek Automotive managing director Neil Heslington
At the core of the powertrain is Zytek’s new, high efficiency permanent magnet synchronous motor. The high maximum machine speed of 14,000 rpm has enabled generated torque and hence machine size to be reduced considerably, bringing further reductions in cost and weight.
|Zytek worked closely with transmission specialist Vocis to develop a compact and light-weight transmission (left, air-cooled motor on the right) for its new EV powertrain. Click to enlarge.|
When used in conjunction with the Zytek Electric Vehicle Control Module, torque delivery is scheduled in a way that further improves overall efficiency, while also eliminating the harshness that can occur during changes in torque demand.
Parallel design and integration of the major subsystems has allowed a high level of optimization. An example is the integration of the charger within the inverter, reducing the number of separate enclosures and connectors required in the vehicle, reducing cost and increasing reliability.
A new transmission, designed specifically for use with the new electric machine, is being developed by transmission specialist Vocis.
We are working closely with Zytek to ensure that the motor and gearbox are optimized as a single system, delivering maximum efficiency and installation flexibility with minimum cost, weight and packaging requirement. The width across the gearbox is just 138cm and transmission weight is only 10kg, which we have achieved without any compromise in performance. Testing has already shown that this is a very robust unit that delivers excellent durability and refinement.
—Vocis managing director Mike Everitt
The compact dimensions of the new drivetrain make mechanical integration with the vehicle much simpler. The main connections required are High Voltage (to the traction battery) and Low Voltage (for electrical interface with the vehicle). The air cooling option brings a further substantial contribution to reducing weight and complexity by potentially eliminating the entire water cooling system.
The Zytek electric vehicle control module interfaces with all standard vehicle systems such as ABS (Antilock Braking System) and ESP (Electronic Stability Programme). It also provides the complete range of expected diagnostic information as well as its own range of diagnostic codes.
As the homologation environment for electric vehicles is not yet mature, Zytek is experienced in analysing the many SAE and international standards that provide overlapping information on many aspects of electric vehicle safety, in order to provide a vehicle that is suitable for volume sales in all major world markets. All of our new powertrains are being designed to accommodate the most likely type-approval scenarios.
—Engineering program manager Neil Cheeseman
Zytek has designed and integrated electric drive systems for a wide range of European and US vehicle manufacturers and is currently building high performance electric drivetrains up to 70 kW and 300 N·m for cars, buses and light commercial vehicles. Their UK facility can accommodate up to 6,000 E-Drive integrations a year in batches as low as 100, providing vehicle manufacturers and large fleets with a highly flexible specialist production resource for their low carbon programs. Zytek can also manufacture up to around 18,000 high efficiency electric traction motors each year, with the option of integrated control systems to further improve overall system weight and packaging.
The design and build of 100 first generation smart ed electric vehicles was managed by Zytek, including support for fleet trials, and the company is now working with smart to manufacture the second generation electric vehicle at ‘smartville’ in Hambach, France.
In October 2009, Zytek was selected to provide a highly integrated 70 kW powertrain to a new joint venture company being established by US truck supplier Navistar and British electric commercial vehicle specialist Modec. (Earlier post.)