Performance of a nine-phase synchronous reluctance drive

This paper describes the performance of an experimental 5 kW nine-phase synchronous reluctance motor (Syncrel) drive. Increasing the number or phases or the Syncrel above three allows the stator MMF's to be shaped, producing significantly greater torque/RMS ampere in the same volume machine. Generalized dq voltage and torque equations are derived for the nine-phase Syncrel. These demonstrate that harmonic direct and quadrature components of current contribute to torque production in the machine and can be controlled by applying appropriate stator voltages. A field-oriented controller is described and implemented using a TMS320C32 digital signal processor board. The controller designates portions of the stator winding as supplying either direct or quadrature excitation. A simple inverter switching strategy is used to control the phase currents to their reference values. An alternative control strategy based on the transformed d-q harmonic components of stator current and voltage is also presented. Experimental and simulation results are provided for both controllers.