Detailed Analytical Modeling of Fractional-Slot Concentrated-Wound Interior Permanent Magnet Machines for Prediction of Torque Ripple

Electromagnetic torque in interior permanent magnet machines is a function of their inductances and permanent magnet (PM) flux linkages, which are assumed sinusoidal in the standard dq model of the machine. This assumption is flawed when a fractional-slot concentrated-wound stator is utilized, because its nonsinusoidal winding function leads to harmonics in the machine parameters. In order to address this deficiency, the nonsinusoidal machine parameters are modeled in this paper, based on which, a modified extended dq model is proposed. The harmonics in the machine parameters are included in the proposed modified extended dq model and their effects on the machine operational characteristics are accounted for. Detailed equations for the average torque and torque ripple are then derived based on the proposed modified extended dq model. Experimental tests are also described for the measurement of the proposed modified extended dq model parameters. The estimated torque and torque ripple by the proposed model are validated through experimental tests on a prototype fractional-slot concentrated-wound interior permanent magnet machine.