Position estimation at starting and lower speed in three-phase switched reluctance machines using pulse injection and two thresholds

This paper presents a method of indirect position estimation for three-phase switched reluctance machines suitable for starting and lower speed operation. Rotor position estimation is accomplished by injecting a pulse current whose amplitude is compared with two different thresholds. The rotor position of the three-phase SRM is identified in terms of six sectors for one electrical revolution of the rotor. The sector of machine operation is obtained by comparing the pulse current amplitude for the phase with the two thresholds. Each sector is unique and identifies which phase has to be used for sensing and which phase has to be used for powering the SRM. The sector information is used for both starting and continuous rotation of the SRM. This two threshold level comparison and the associated algorithm avoid the low resolution issue of position estimation with pulse injection in a three-phase SRM. Experimental results are given to demonstrate the method.