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Multi-phase permanent magnet motors are becoming popular in various applications such as high power traction which require low cogging and torque ripple, and reduced noise and vibration. This paper presents the development process of a full order detailed mathematical model for an unconventional nine-phase permanent magnet (PM) motor with asymmetric AC windings. The phase inductances are calculated based on the individual winding functions. Using these parameters, electrical equations for each phase based on the voltages and flux linkages are generated. These equations are transformed into an arbitrary reference frame and the torque equations are developed for the 9-phase motor. A Matlab-Simulink model is then developed for the proposed nine-phase PM motor based on the developed dynamic equations. Finally, the model is validated with the finite element analysis and laboratory testing of the prototype motor. It is shown that the developed mathematical model can be used for such complex asymmetric winding multi-phase PM motors.