DRIVE CIRCUIT FOR PERMANENT MAGNET MOTOR

摘要

PROBLEM TO BE SOLVED: To provide an improved drive circuit for an electric motor which achieves high efficiency or at least provides a useful choice.SOLUTION: A drive circuit for an electric motor having a wound stator and a permanent magnet rotor includes a controllable bidirectional AC switch connected in series with a stator winding between two terminals for connecting to an AC power supply. First and second position sensors detect positions of magnetic poles of the permanent magnet rotor. A voltage regulating circuit is connected between the two terminals and the controllable bidirectional AC switch and configured to supply electric power to the first position sensor during the positive cycle of the AC power supply and to the second position sensor during the negative cycle of the AC power supply so that the controllable bidirectional AC switch is switched between a conductive state and a non-conductive state in a predetermined manner thus enabling the stator to rotate the rotor in only one predetermined direction during start-up.SELECTED DRAWING: Figure 3