Canadian firm develops new high-performance electric drive systems

  • 10-Mar-2010 10:48 EST
tm4_motive_P1.jpg
The TM4 MOTIVE permanent magnet motor from Canada's TM4 was selected by India's Tata Motors to power its first electric vehicle, the Indica Vista.

The TM4 MФTIVE permanent magnet electric motor offers advanced electric drive design to niche-sized EV manufacturers, said Eric Azeroual, TM4's business development manager. The TM4 system, a small, lightweight, and cost-efficient powerplant suitable for all-electric or plug-in hybrid vehicles, will be featured at the 2010 SAE World Congress in Detroit.

The e-motor has been available to selected customers for a little over a year. It boasts the best power-to-weight ratio in its class and industry-leading energy efficiency, according to Canada-based TM4, which is a subsidiary of Hydro-Québec, a hydroelectric power utility.

The company has capacity to produce 10,000 e-drives per year. Its motor designs range from 10 kW (for golf carts) to 660 kW (wind generation and marine applications). Prototypes of the latter are now under test.

Last year India’s Tata Motors purchased 110 TM4 MФTIVE motors to power its first electric vehicle, the Indica Vista, which the automaker's Vice Chairman, Ravi Kant, has said will be introduced in Europe later this year.

Miljø Innovasjon, a Norwegian subsidiary of Tata Motors, selected TM4 to provide power electronics and its NEURФ vehicle controllers, in addition to the e-motors. Canada’s Electrovaya is supplying the Vista's lithium-ion batteries.

Tata showed an electric Nano concept car powered by a TM4 drive system at the 2010 Geneva Auto Show. The Nano EV replaces the standard Nano's rear-mounted gasoline engine with a 240-volt/400-amp electric motor. Its power comes from a 12-kWh lithium-ion battery pack developed by Miljø Innovasjon. 

The four-passenger Nano EV, which can go up to 100 miles (161 km) on a single charge, is no performance car, though, accelerating from zero to 37 mph in “under 10 seconds,” according to the manufacturer.

TM4 has other similar motor-supply programs in the works, noted Azeroual. With funding from Sustainable Development Technology Canada (SDTC), a not-for-profit foundation, the firm is working with Magna Electronics to design, develop, and demonstrate a new electric powertrain, for example.

The MФTIVE design is the result of a decade of R&D on advanced, high-performance electric motors at TM4, which made its name in the late 1990s with a innovative in-wheel or wheel hub motor developed originally by the Canadian inventor and engineer Pierre Couture.

To maximize torque, the design uses reverse-order topology, an inside-out layout wherein the rotor spins outside of the stator. This configuration increases the radius from the hub to rotor, which provides more moment or leverage, explained Azeroual.

“The advanced in-wheel motor led to numerous patents related to compact design and torque control,” he said. “When we addressed a motor for conventional applications where the power plant is located in the central part of vehicle or on the rear axle like the MФTIVE, we decided to ‘de-telescope’ the reversed configuration, but still retain the many of the best features of the earlier motor.”

He cites the motor's +10,000-rpm shaft speeds as a key differentiator. "The faster a motor spins, the higher its power density, the smaller it can be and the cheaper it ends up being,” Azeroual said.

The MФ 120 system, which weighs 32 kg (70.5 lb), offers 120-kW maximum power, with 37 kW continuous power. Claimed peak torque is 170 N·m (125 lb·ft), with 78 N·m (57.7 lb·ft) continuous. It has a maximum 4.6 kW/kg power-to-weight ratio.

The motor offers 96% efficiency at nominal operation, the company claims. Cooling is provided by 40/60% water/glycol system.

Azeroual also highlighted the high packing density of the TM4 MФTIVE’s flat wire-windings.

“We have strong patents on a unique shape that results in shorter end windings, areas that don’t generate power,” he said, adding that the special shape further boosts power density and efficiency, yielding a lighter motor that produces less heat.

All TM4 products are designed to work with a "smart" charging grid.

Hydro-Québec intends to set up a joint venture with a global-scale auto parts manufacturer to facilitate the mass production and marketing of the TM4 MФTIVE electric powertrains.

“We’re looking to find a manufacturing partner to scale up production,” Azeroual reported. “Right now, we’re using our current motor production to work on continuous process improvement.”

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