A capacitively powered motor and constant speed control therefor

摘要

A capacitively powered motor having a power switching circuit (108) adapted to be connected (L1,L2) between a power source and its winding (106) for selectively energizing the winding to generate a magnetic field which causes a rotating assembly (102) to rotate. A position sensing circuit (112) provides a position signal representative of the position of the rotating assembly and a commutating circuit (110) controls the power switching circuit to commutate the power switching circuit at a commutating angle and at a substantially constant duty cycle to achieve a desired rotating speed of the rotating assembly. The commutating circuit varies the commutating angle in response to the position signal to maintain the substantially constant rotating speed of the rotating assembly. As result, the efficiency of the motor is varied to maintain the substantially constant rotating speed.