Sensorless multiphase induction motor drive based on a speed observer operating with third-order field harmonics

This paper presents an electric drive consisting of a multiphase induction motor fed by multiphase inverter. The control system is similar to that of a traditional field-oriented control for three-phase motors, but the machine state is determined by a novel sensorless observer. Since multiphase motors with M phases (M is supposed odd) have the capability of controlling the spatial harmonics of the magnetic field up to the (M-2)th order, the proposed observer excites the third-order spatial harmonic of the magnetic field to estimate the rotor speed. Experimental results are provided to show the feasibility of the electric drive.