Eddy-Current Losses in the Solid Back-Iron of PM Machines for different Concentrated Fractional Pitch Windings

Permanent magnet (PM) machines with concentrated fractional-pitch stator windings are increasingly used because of their cost-effectiveness. In this paper, the eddy-current losses in the solid back-iron of these machines are modeled. This model is applied to calculate the losses in the solid back-iron of the linear PM generator of the Archimedes wave swing (AWS) for different combinations of numbers of poles and numbers of teeth. In machines with fractional-pitch windings, these eddy-current losses are considerable and depend strongly on the combination of number of teeth and number of poles. In fractional pitch machines with a coil around very second tooth, these losses are excessive.