Remy HVH windings have a shorter end turn space than conventional round wires and are well-suited to liquid cooling. Source: Remy. Click to enlarge.

Remy International, Inc. is supplying Daimler with HVH (High Voltage Hairpin) electric motors for the two-mode hybrid transmissions used in the 2010 Mercedes-Benz ML450 Hybrid (earlier post) recently released to the United States market.

The HVH technology provides improved motor performance and cooling effectiveness, enabling increased range in all-electric drive mode and the potential for a smaller internal combustion engine. The technology is also used in GM’s current generation of two-mode hybrid SUVs and trucks in the US, as well as BMW’s, according to Remy.

(GM recently announced that it would begin designing and producing electric motors itself, with the first application to be in the next-generation rear-wheel drive two-mode transmission, starting in 2013. Earlier post.)

In contrast to conventional roundwire windings, the HVH stator winding uses precision-formed rectangular wires. Multiple layers of interlocking “hairpins”

produce a slot fill of up to 73% vs. 40% for typical round-wire windings. This design also creates a shorter end turn space than round-wire stators, thereby reducing heat and improving the motor’s torque and power density. It also lends itself to robust construction at the connections between the conductors.

Combined, the high slot fill and shorter

end turn space reduce the winding resistance causing less heat

generation. The HVH windings are well-suited to liquid cooling

that further enhances performance and reliability.

Remy cites testing showing that an HVH internal permanent magnet motor provides 27% higher torque and 34% higher power compared with the same size round wire winding IPM

motor. At the same performance level, the HVH motor offers a 22% reduction in space requirements and 13% reduction in mass. In addition to documented fuel efficiency improvements, freight hauling capacity can be increased since more weight can be

carried in the vehicle rather than in the hybrid drivetrain.

The HVH stator design is compatible with both permanent magnet and AC induction rotors; gains in AC induction machines are similar to those of the permanent magnet motors, Remy says. Remy manufactures hybrid motors with both types of rotor construction, offering its customers options in performance and cost.

Remy is supplying two HVH electric motors per ML 450 hybrid vehicle. The first motor is positioned close to the internal combustion engine and is used both as a motor and generator, providing more than 80 hp (60 kW) to assist the drivetrain or charge the vehicle battery. The second motor located at the output end of the transmission generates 80 hp (60 kW) and 192 lb-ft (260 N·m) of torque and is tuned for maximum electric drive performance plus recovery of regenerative braking energy to the battery.

The two-mode hybrid transmission in the ML450 Hybrid works together with a 3.5-liter V6 engine to attain improved fuel efficiency over comparably powered sports utility vehicles. Around town, the ML450 Hybrid can operate as a zero-emission vehicle when powered by its electric drive alone. Using a modified Atkinson cycle for maximum fuel efficiency, the V6 engine kicks in when needed and when accelerating on a freeway entrance ramp for example, the electric drive and combustion engine work together for a total of 335 hp (250 kW).

The Remy HVH motors for the Mercedes ML450 Hybrid will be manufactured at Remy’s manufacturing plant in Mezokovesd, Hungary. The Mercedes ML450 Hybrid will be produced at the Mercedes manufacturing plant in Tuscaloosa, Alabama.

Remy offers two basic off-the-shelf model series of its HVH motors: the HVH410 motors, and the HVH250 motors, introduced in October 2009. The HVH410 series is targeted at applications such as medium- and heavy-duty trucks, as well as off-highway vehicles. Offered as either a permanent magnet or induction motor, it is suited for traction motor, generator or motor/generator applications, Remy says.

The new HVH 250 series applies the hairpin stator technology in a smaller footprint and lighter weight, also suited for traction motor, generator or motor/generator applications.

In August 2009, Remy was selected to receive a $60.2-million grant as part of the $2.4 billion in funding awarded to 48 next generation battery and electric vehicles projects by the Department of Energy. (Earlier post.)

Remy will use the funds to expand its products and production, and to expand its hybrid testing lab. The grant will also help Remy assist customers in applying these HVH motor/generators to their vehicles. NRE (non-recurring engineering), tooling, and software for mot application and integration into the vehicle are included in the grant.

Resources

• Inside the HVH Hybrid Motor