| 摘要 |
A method and controller for electronically commutating a permanent magnet brushless dc motor ( 21 ) under closed loop control where current is commutated ( 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 the three stator windings whenever that winding has no applied current flowing in 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 factor of 3.
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