Longya Xu, Power Electronics and Electric Machine Group, The Ohio State University
The PM machine for a direct-driven wind turbine generator features a high power rating of 2MW with a low speed range of 10-20 rpm, constrained by wind turbine blades 100 meters in diameter. The rated generator torque is high, approaching 1 mega Nm and demands a huge PM machine design. However, with optimally designed torque density, the PM generator can be made reasonably small. It is designed to be directly proportional to the torque capability
Two types of PM direct-driven wind power generators have been designed, one with an inner rotor and another with outer rotors. Both have a torque of about 870,000 Nm with a phase current of 1700 amps and energy efficiency as high as 97%. The outer rotor design has mechanical advantages. Figure 11 shows the results from a finite element investigation demonstrating the magnetic design of both PM generator types.
This research is supported by the Grainger Center for Electric Machinery and Electromechanics.