SINGLE WINDING BACK EMF SENSING BRUSHLESS DC MOTOR

摘要

A method and controller for electronically commutating a permanent magnet brushless dc motor (21) under closed loop control where current is commutate d (22) through successive combinations of two out of three stator windings to produce a rotating flux. Commutations are determined by each 60~ angular position of the rotor by sensing the back EMF (24) induced in only one of th e three stator windings whenever that winding has no applied current flowing i n it to determine the 0~ and 180~ positions and extrapolating the 60~, 120~, 240~ and 300~ positions by dividing the time interval therebetween by a fact or of 3.