At the 2013 SAE World Congress in Detroit, Protean Electric announced its production in-wheel electric drive system. The announcement comes one year after it first showed the prototype technology at the 2012 event. The system, which includes motors that fit within a pair or all wheels of a vehicle, is designed to be an integral part of a hybrid powertrain system when paired with a traditional internal-combustion engine, or it could be the only source of traction drive in pure electric vehicles.
“Our system can be applied to current vehicle platforms, retrofitted to existing vehicles, or used to create all new architectures for the future,” said Bob Purcell, Chairman and CEO of Protean Electric. Purcell was previously with General Motors for 27 years, eight of which he spent running the Advanced Technology Vehicles group that produced the ground-breaking electric EV1 car and S10 truck.
Since the SAE 2012 World Congress, “the big news is we closed the C Series round investment,” said Purcell. In July of last year Silicon Valley venture capital firm Oak Investment Partners was joined by China-based GSR Ventures, New Times Group, and the city of Liyang, Jiangsu Province, China, with $84 million to bring the electric drive technology to production in Liyang.
In the past year company engineers have also made improvements in two main technical areas for the production version of the motor, said Ken Stewart, Vice President of Business Development.
“We tuned the motor to have higher torque because low-end torque is always good,” he said. “We went from 800 to 1000 N·m peak torque.” Peak power remains at 75 kW, “which is still plenty powerful,” he added.
Company engineers also expanded the motor system’s efficiency envelope so that a vehicle can run in its optimal range as much as possible during the duty cycle.
“We were able to expand the peak efficiency of the motor so that we are over 90% efficient for a much larger portion of vehicle driving range now,” said Stewart. “We use less energy to get the vehicle to run down the road, so that means less battery electricity consumption.”
The motor’s high output and relatively low mass of 31 kg (68 lb) means that Protean can claim the highest torque density of any leading electric drive motor. In addition, the company claims that its motor has better regenerative braking capabilities than the competition, allowing up to 85% of the available kinetic energy to be recovered during braking.
Skeptics might say that adding so much unsprung mass to at least two or maybe four corners of a vehicle could be detrimental to ride and performance. However, Protean tests indicate that the addition “is a manageable amount,” said Stewart. “So you can take conventional engineering methods of tuning the car for shocks, struts, valving, damping, and you can still make a pretty sweet car even though you’ve added the extra mass.”
Some competitors have proposed inboard mounting to get around the issue, but according to Stewart: “Our advantage is the architecture of the motor, the rotor on the outside. The cross section of the motor is what’s key. That’s a perfect design for in the wheel. I don’t really want to compete with the guys who are going inboard because we have better torque density, power density. They can’t go in the wheel and we can. They can’t provide the flat floor and we can. So that’s our sweet spot.”
Protean has been awarded 27 patents for the in-wheel technology, with 84 additional international patent applications pending. Ten of those 27 patents have been awarded since the 2012 SAE World Congress, ranging from electric motor cooling, combining regenerative with electromechanical braking, attaching the in-wheel electric motor with dual-disc calipers, and a “submotor” architecture concept that Stewart says is one of the key enablers of its technology.
One OEM vehicle project is looking into using Protean motor technology to replace rear friction brakes entirely while showing compliance with safety regulations and standards. The Protean motor’s braking torque capability exceeds optimum braking torque requirements of almost all vehicles up to 2000-kg (4400-lb) GVW and many more beyond that mass. The submotor architecture allows this level of total machine torque without potentially destabilizing fault torque under a single point or random failure—only a quarter of the machine can fail at any one time.
Protean has developed multiple demonstration vehicles, including a Vauxhall Vivaro cargo van, a Ford F150 pickup truck, Brabus Mercedes-Benz E-Class-based full electric and hybrid vehicles, and Guangzhou Automobile Industry Group Trumpchi sedan.
China is Protean’s initial target market for the motor because “that’s where the most compelling need is in the world,” said Purcell. Influencing factors include poor air quality, population growth, and economic development there—and the “government is also taking a very constructive view trying to help make [new energy vehicles] happen,” said Purcell.
The plug-and-play nature of the company’s motor concept offers a transitional solution for China automakers, “keeping the vehicle portfolio largely intact and supplementing it with electric-drive technology,” said Purcell. “We can take a traditional internal-combustion vehicle, package a pair of our motors and a battery pack on that same vehicle, leaving the combustion-based powertrain in place, and at the push of a button you could drive that vehicle electrically in the city.”
Purcell says ideal launch applications would be light commercial vehicles in delivery and service industries, executive and passenger vans for shuttling people, and then executive sedans.
The motor system is undergoing final validation now in an engineering fleet running the motors in-vehicle, said Purcell. Protean has completed the design of its manufacturing system, tools are being produced at its partner’s facility in Munich, Germany, and it is “now doing run-off on the actual production stations that would go in our first factory,” he added.
Prototype motor production will begin in China in the fourth quarter of this year, with volume production commencing about this time next year.