Protean Electric and FAW-VW developing production-intent electric propulsion system with in-wheel motors
|Cutaway of the Protean Electric in-wheel motor. Click to enlarge.|
In-wheel electric drive developer Protean Electric is partnering with FAW-Volkswagen Automotive Co., Ltd. (FAW-VW) in China to develop a new electric propulsion system that will include Protean Electric’s Protean Drive with intent towards a demonstration vehicle program and production.
FAW-VW will create a new rear-wheel drivetrain for an electric vehicle (EV) based on the new Bora compact sedan, utilizing two Protean in-wheel motors. This cooperation began several months ago; all bench testing, engineering calibration and on-site application support is expected to be completed within a year. Protean Electric will also assist FAW-VW in the development of safety and vehicle controls that can be applied to additional vehicle programs.
This is a two-phase project that will capitalize on the torque and packaging freedoms that Protean Drive can bring to an automaker. Our technology will return the space to the new Bora vehicle platform that was formerly occupied by an in-board motor and powertrain.—Kwok-yin Chan, CEO of Protean Holdings Corp.
Protean Electric introduced its production in-wheel motor at the 2013 Society of Automotive Engineers World Congress in Detroit. Volume production is targeted to begin in 2014, out of Protean’s new manufacturing facility in Liyang, China.
The permanent magnet synchronous motors reside in the space behind the wheel. Protean’s new production motor provides a 25% increase in peak torque compared with the previous generation’s design and can deliver peak output 1,000 N·m (735 lb-ft) and 75 kW (100 hp), with 700 N·m (516 lb-ft) and 54 kW (72 hp) continuous. (Earlier post.) Protean says that its new production motor provides the highest torque and power density of any leading electric propulsion system.
In a paper presented at the EVS 27 conference in Barcelona, Gareth Roberts from Protean and Alessandro Galeazzi from SKF Automotive (a strategic partner of Protean), noted that:
The performance gain with respect to other more conventional arrangements is due to the full integration and synergies created with the mechanical components and in particular the wheel bearing. The final performance is connected to the ability of the wheel bearing to provide the required stiffness that controls the reduction of the air gap between the motor rotor and stator.
… There are three geometric factors that make up the motor air gap: the diameter Z, the motor length X and air gap length Y. For motor performance, it is desirable to maximise the diameter and motor length and minimise the air gap length.
The control of this air gap under different operating conditions is vital to ensuring efficiency and high levels of performance targeted by the In-Wheel motor. Road loads in their worst cases however, represent a significant challenge in maintaining the optimum level of air gap, hence the need to tightly control its variation. Furthermore, there is a risk of magnets touching the wound teeth if too much variation is allowed, with serious consequences for mechanical damage, performance and durability of the In-Wheel motor. The wheel bearing design and in particular the tilting stiffness, influence the design of the motor length and airgap length, which in turn influence the motor performance.
Protean engineers inverted the conventional motor design; the rotor is on the outside and the stator on the inside. This improves performance, makes it compact, and provides space inside the motor for power electronics and controls, the company says.
Each in-wheel motor, with an operating range of 200 - 400 Vdc, comes with its own integrated power and control electronics, which communicates with the vehicle by utilizing a common vehicle control system. Other features of Protean’s in-wheel motors include:
- Mass of only 34 kg (75 lbs.) per motor
- Integrated friction brake
- Superior regenerative braking capabilities, which allow up to 85% of the available kinetic energy to be recovered during braking
- Fits within a conventional 18" road wheel
Protean has developed multiple vehicles with various global OEMs for demonstration in the US, Europe and China.
Protean has been awarded 33 patents for its technology and design, with 101 additional international patent applications pending.
Protean is funded by Oak Investment Partners, GSR Ventures and Jiangsu New Times Holding Group Co., Ltd. Protean Electric has operations in the United States, United Kingdom, China and Hong Kong.
The FAW-Volkswagen Automotive Company (FAW-VW) was founded in 1991 and is a Chinese joint venture between FAW Group Corporation, a Chinese state-owned automotive manufacturing company and Volkswagen Group. On 15 August 2011, FAW-VW celebrated its twentieth anniversary with a milestone of producing its one millionth car.
Alessandro Galeazzi and Gareth Roberts (2013) “Influence of wheel bearing performance on In-wheel motor advanced applications” (EVS 27)
Tim Martin and Richard Burke (2013) “Practical Field Weakening Current Vector Control Calculations for PMSM in Vehicle Applications” (EVS 27)