Comparison of Slip Permanent Magnet Coupler Topologies for Slip-Synchronous Wind Turbines

In this paper, a newly proposed design optimization strategy for slip permanent-magnet couplers (S-PMCs) is used to compare the performance of various S-PMC topologies. All S-PMC topologies investigated hitherto have been open slot surface-mounted magnet topologies and have been mostly evaluated at only one (and very much the same) rated slip percentage and only aluminium as rotor coil material. In this paper, therefore, alternative S-PMC topologies are considered over a wide range of rated slip percentages and for different rotor coil materials. The study shows that surface-mounted magnet topologies provide the highest pullout torque, semi-closed slot topologies ensure a reduction in active mass and magnet mass, and spoke pole magnet topologies are not suited for this application. Further, if wind turbine system dynamics allow for low-rated slip percentages, then copper must be used as coil material. However, if system dynamics require a relatively high-rated slip percentage, then aluminium (and, if feasible, tungsten) should be used as the coil material.