GE engineers have designed a new monster motor for testing wind turbines capable of generating extreme torques produced by gale force winds and nasty offshore storms. “It’s basically a huge wind turbine in reverse,” says Franz Hubl, global business leader for test systems at GE Power Conversion. “It generates torque instead of electricity. We can put a lifetime of stress on a wind turbine prototype in just 200 days.”
New test bed can exert a lifetime of stress on a wind turbine prototype in just 200 days.
At the heart of the motor is a huge permanent magnet made from an alloy of rare-earth elements. It can generate 20,000 horsepower (the equivalent of 150 cars) and drive the shaft at 10 to 20 rotations per minute. That’s double what a large wind turbine can typically experience on a breezy day. The motor is so large, 26 feet in diameter and 330 tons, that it had to be assembled on site.
It will power a brand new wind turbine test bed at the National Renewable Energy Center (NAREC) in Blyth, UK. The motor will work in combination with a sophisticated testing system manufactured by the American firm MTS. The MTS hydraulics and mechanical system attaches to the front of the wind turbine like a giant three-prong steel mandible that distributes the torque unevenly in simulation of extreme conditions. “We can expose the turbines to as much as twice the overload,” Hubl says. “When you have a turbine that’s 150 meters in diameter, a sudden gale can apply tremendous asymmetrical load on the bearings at the center of the turbine. The wind speed at the top of the blades will be higher than at the bottom. Now we can simulate those conditions.”
The assembly can test an entire nacelle, the large grey box sitting atop of the wind turbine tower and housing the electricity generation system.
The system will replace older technology using standard electrical motors. Those motors were spinning at 1,500 rpm and engineers had to slow them down to wind speed rotation with elaborate gearboxes.