Performance evaluation 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 of phases of the Syncrel above three allows the stator MMFs to be shaped, producing significantly greater torque/RMS ampere in the same volume machine. Generalized d-q 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. Experimental current regulation, speed response and torque measurements are presented from the drive. These results validate the system model and demonstrate the drive capability.