Auto transmissions to slash motor sizes in electric hybrids 23 June 2010

Automatic gearboxes can improve the efficiency of hybrid-electric military vehicles, says automatic transmission specialist Antonov.

Antonov chief commercial officer Simon Roberts also suggests that they can enable significant downsizing of electric drive motors as well.

"A three-speed transmission coupled to a 400Nm electric motor can easily match the performance of a 900Nm motor with no transmission," says Roberts.

"The latter is like putting a huge V8 engine into a dragster: it delivers so much power and torque that you can throw away the gearbox – but it's not very fuel efficient," he adds.

Roberts suggests that's why the automotive industry trend is to downsize the engine and match it to an efficient transmission and driveline. "And it's the same principle for traction motors, though in practice not yet generally applied," he says.

He makes the point that smaller and lighter electrical machines use less aluminium, copper and steel. They also require smaller batteries and reduce the need for highly-rated power electronics.

The company's latest engineering contract, awarded by the MoD, addresses the issue of vehicle electrical power, with the development of a two-speed alternator for military and commercial vehicle applications.

Roberts says that with two speeds available, the alternator can match the output in the low speed range of a larger and more expensive single-speed alternator, but it also has the potential of replacing multiple alternators, often required for heavy-duty military vehicle applications.

With the design concept already signed off, the project has moved into detailed engineering design. Roberts explains that the alternator will provide full electronic control of the speed change through an active clutch mechanism. It will offer increased electrical power on demand at low engine speed, ensuring optimal battery charge and allowing additional equipment to be specified.

Incidentally, the company has also been awarded a project by the UK's Technology Strategy Board to design and develop a high efficiency three-speed powershift transmission suitable for hybrid electric vehicles, which Roberts believes could also be applied to military vehicles.

This transmission will initially feature in Jaguar's high profile Limo-Green electric vehicle research project. "The three-speed transmission can be coupled to a much smaller electrical motor, yet deliver acceleration and top speed comparable to a conventional powertrain," says Roberts.

"The efficiency curve of an electric motor is far more pronounced than the torque curve, so the major benefit of a multi-speed transmission is to keep the motor operating as close as possible to its most efficient speed, which will increase the vehicle range."

Author
Brian Tinham

Related Companies
Antonov plc

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