Phase Advance Approach to Expand the Speed Range of Brushless DC Motor

In order to extend the speed range of a brushless DC motor drive, it is common to control the phase current to lead the phase back EMF by an "advance angle". It is based on the "phase advance approach", which was proposed for brushless DC motor drive in 1995. This paper completes the "phase advance approach" theory in several aspects: a) the stator resistance is taken into account in the analysis and calculation of phase reference current; b) the situation where the back EMF is smaller than the applied voltage is also taken into consideration; and c) an analytical equation to calculate the advance angle is also derived. The obtained equation are therefore more general than those in the prior art. Extended simulation results demonstrate the validity of the approach.