Segmented permanent magnet synchronous machines for wind energy conversion system

Direct-drive generators are appealing candidates for some wind energy conversion systems (WECS) since they provide a means of eliminating the gearbox from the drivetrain. However, a fundamental problem associated with these machines is their large size that makes them difficult to manufacture, transport, and assemble. This paper introduces the concept of segmented permanent magnet (PM) synchronous machines with both single and dual stator/rotor layers that feature a modular structure which makes them appealing candidates for use in direct-drive wind generators. To form a multi-phase machine, a spatial phase-shifting iron piece is inserted between adjacent segments to maintain the appropriate spatial positioning between phases. The segmentation strategy for this type of machine is discussed, considering the trade-offs between average torque production and torque ripple. A nine-phase segmented PM synchronous machine configuration is proposed for reducing torque ripple and improving fault-tolerance capabilities. The performance characteristics of this segmented machine configuration are evaluated using finite element (FE) analysis.