Parasitic losses in modular permanent-magnet generators

A modular arrangement facilitates the construction of multipole, permanent-magnet, direct-coupled generators for large grid-connected wind turbines. However it introduces new forms of loss into the stator and rotor structures due to the periodic spatial variation in the stator back iron permeance. A mathematical model of the modular machine is described in the paper and its predictions are shown to be in agreement with measured losses