Study and verification of a slow speed PM generator with outer rotor for small scale wind turbines

This paper considers the study of a directly driven low-speed permanent magnet synchronous generator specially constructed for a vertical axis wind turbine. The studied PM generator with outer rotor construction offers an alternative to fix the wind turbine directly to the end-disk of rotor. As an advantage of the outer rotor PM generator construction it is easier and more reliable to fix the magnets on the rotor active surface. An analysis to optimize the active length of both stator magnetic core and air-gap has been presented. Cogging torque has been analyzed to reduce it by slot skewing. Electromagnetic simulations of the PM generator were performed by using finite element analysis and the SPEED software. A 5 kVA PM generator was designed, manufactured and tested. The test results of the prototype PM generator have been analyzed and compared with the calculated characteristics and data.