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Machine Design

Copper Motor Rotors Give Army Trucks a Boost

Four 140-hp electric motors power the latest generation of U.S. Army heavy expanded mobility tactical trucks.

Julie Kalista
Online Editor

Oshkosh HEMTT A3 with ProPulse
They use ac induction motors with die-cast copper rotors on each of four axles. The 520-V motors are powered by a 400-hp diesel engine, making a hybrid drive system that can move the 35,000-lb. vehicles and run a 335-kW generator.

Called ProPulse and manufactured by Oshkosh Truck Corp., Oshkosh, WI, the hybrid drive decreases emissions and increases fuel economy by up to 40%, according to the manufacturer. The drive is also configured for commercial refuse vehicles. OshKosh claims the drives lower life-cycle costs and lower interior and exterior noise.

Reliance Electric, Greenville, SC, manufactures the electric motors and the die-cast copper rotor technology is the only way to meet the strict military requirements. The requirements include the ability to climb a 60% incline while carrying a full payload. The new HEMTT A3 is also 3,000 lbs. lighter than its predecessor, but can still carry a 13-ton payload. The truck is can unload cargo from a C-130 aircraft without any extra quipment.

Copper motor rotors are more efficient than traditional aluminum rotors because copper is a better conductor of electricity and has lower resistance. So, motors using copper are smaller and stay cooler. "This induction motor has the highest power density possible today," says Reliance's director of advanced technology. The Army Research Laboratory sponsors the research program.

More Information:
OshKosh Truck Corp.
Reliance Electric

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