Scalability Characteristics of Magnetic Circuit Model for Fractional-Slot Concentrated Winding IPM Machines

Prior work has shown that it is possible to develop a magnetic circuit model (MCM) for fractional-slot concentrated winding (FSCW) interior permanent magnet (IPM) machines that captures the major sources of electromagnetic nonlinearity that are important in this type of machine. This MCM has been defined to incorporate several modularity principles in order to maximize its flexibility for different machine designs. An investigation has been carried out to evaluate the scalability characteristics of this MCM in several key dimensions including power rating, pole/slot number combinations, diameter/length aspect ratio, stator winding configuration, stator phase number, and external/internal rotor configurations. Several FSCW-IPM machine designs that have been evaluated for this scalability investigation, but one example, consisting of a direct-drive 500 kW FSCW-IPM wind turbine generator, is highlighted in this paper. Model delivers promising results as reflected in close matches between predicted flux densities, flux linkages, voltages and torque delivered by the MCM and finite element analyses.