A UK-developed in-wheel vehicle motor, claimed to have the highest torque density (25.8Nm/kg) of any electric propulsion system, has been granted 17 technology and design patents. Protean Electric has applied for more than 60 further global and national patents for its Protean Drive motor.

The direct-drive design avoids the need for gearboxes, drive shafts or differentials. The drive electronics is built into the motor, which fits in the space of a conventional 18-inch road wheel and can be retrofitted to existing vehicles.

Each 31kg in-wheel motor (shown above and below) can deliver 81kW and 800Nm. They provide regenerative braking, allowing up to 85% of the kinetic energy to be recovered during braking. Protean claims that the motors can increase fuel economy by more than 30%, depending on the battery size and the driving cycle.

Protean has demonstrated its in-wheel motors in several light-duty vehicles from small cars to commercial vans. At the 2011 Frankfurt Motor Show, the in-wheel motors were shown on two Brabus vehicles based on Mercedes-Benz E-Class cars: a high-performance four-wheel-drive electric car; and a hybrid vehicle.

The Protean motors have been purpose-designed from scratch. “We started with a clean sheet and designed motors specifically for in-wheel applications,” says Protean Electric chairman and CEO, Bob Purcell.

“Our message to the industry is simple,” he adds. “If they want to pursue in-wheel motors, they will naturally come to the same design and development conclusions as we did, and we have an exceptional solution that is clearly ahead of the rest of the industry.

“We are already working with a number of potential partners to license them our technology,” Purcell continues, “and are looking to create additional partnerships across the global auto industry.”

Protean Electric can trace its history back to 1963 when Printed Motors (PML) was established to design and produce printed armature motors. In 1989, PML merged with Flightlink Controls to form PML Flightlink, which started work on in-wheel motors in 2003. In 2007, the California-based venture capital firm Oak Investment Partners made an initial investment in PML Flightlink, followed by outright purchase of the business in 2009. The original printed armatures operation was sold off and renamed as Printed Motor Works, while the in-wheel business was rebranded Protean Electric. A US head office was established in 2010, but the engineering operation remains in the UK, at Farnham in Surrey.