Eddy-Current Losses in the Solid Back-Iron of Permanent-Magnet Machines with Concentrated Fractional Pitch Windings

The objective of this paper is to calculate the eddy-current losses in the solid back-iron of permanent-magnet (PM) machines with concentrated fractional-pitch stator windings. PM machines with fractional-pitch stator windings are increasingly used a lot because of their cost-effectiveness. The paper derives a model for these eddy-current losses. Although the correlation between the model and the measurements is not perfect, some important conclusions can be drawn. In machines with full-pitch distributed windings, the eddy-current losses in the back-iron are negligible, while in machines with fractional-pitch windings, these losses are too high to be acceptable.