Sensorless controls of a 7-phase bi-harmonic Surface-mounted PM Machine

This paper deals with the position sensorless controls of a seven-phase bi-harmonic Surface-mounted PM machine. Due to its tooth-concentrated winding and its particular magnet segmentation, this fault-tolerant machine is characterized by an electromotive force (emf) for which the fundamental and the third harmonic are of the same order. This specificity should improve the ability of the machine to operate without position sensor. Furthermore, as the virtual machines (denoted h1, h3 and h5 machines) that are used to control the 7-phase machine have quasi-sinewave back-emfs, several so-called emf-methods to sense the rotor position are available. For h1, h3 and h1h3 controls with a Phase-locked Loop (PLL) to estimate the position, the time simulations of the drive confirm the ability of the machine to operate without position sensor while ensuring low torque ripple and quite unchanged current waveforms. An experimental evidence of this property is given for sensorless h3-control (where the back-emf fundamental is used to sense the position).