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Outer-rotor motors power a 4WD sportscar
Published:  01 September, 2005

Outer-rotor motors power a 4WD sportscar

Mitsubishi Motors has produced a prototype electrically powered version of its Lancer Evolution IX high-performance sportscar, driven by four specially developed in-wheel motors. The car, which is capable of 180 km/h, should be able to deliver more than 2kNm of low-speed torque - at least four times more than the standard model. No acceleration figures have been revealed yet.

The four 50kW wheel motors have a novel outer-rotor design with a hollow space at the centre that accommodates the vehicle`s brakes. The permanent magnet synchronous motors are adapted versions of Toyo Denki Seizo machines, each producing 518Nm of torque.

The outer-rotor construction has several advantages. It makes it easier to raise the power output and torque, and eliminates the need for a speed reducer which, in turn, makes the motor easier to fit into the wheel arch. It also avoids the problems of interference with the steering mechanism which have previously made its difficult to use in-wheel motors for front-wheel drive.

A few months ago, Mitsubishi produced an electrically driven version of its Colt car, but this was limited to rear-wheel drive because it used a conventional outer-stator design.

The Lancer Evolution MIEV (Mitsubishi In-wheel motor Electric Vehicle) is purely electric vehicle, powered by a 95Ah, 14.8V lithium-ion battery that fits in the space normally occupied by the drivetrain components. The battery is said to provide a range of 250km.

To produce the electric Evolution (above), Mitsubishi has removed the engine, gearbox, differentials, driveshaft and fuel tank from a conventional car. The two versions have similar power rating of around 200kW and the electric version weighs about 130kg more.

Mitsubishi is planning to market an MIEV using in-wheel motors and lithium-ion batteries by 2010. Before then, its aims to boost the performance and reduce the weight and size of the electric drivetrain further. It also plans extensive tests to see how the in-wheel motors withstand exposure to water, sand and dirt.

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