Abstract: The invention relates to a control circuit for a brushless self-starting D.C. motor of the type which has a permanent magnet rotor and a stator coil, a magnetic field-dependent component subjected to the rotor field to determine the rotary position, and a controllable electronic servo-element lying in series with the stator coil at the D.C. source, the servo-element controlling the flux through the stator coil in dependence on the rotary position of the rotor, the magnetic field-dependent parameter changes of the magnetic field-dependent component being convertible to a control signal for the servo-element. The control circuit is characterized by including an oscillator with an LC resonance circuit of which the inductance is formed by the magnetic field-dependent component in the form of a sensing coil (10) with a core. The circuit includes a modulator for modulating the oscillation of the oscillator in response to the induction brought about in the sensing coil by the torot field.

Abstract: The invention relates to a brushless self-starting D.C. motor assembly of the type having a rotor with a permanent magnet providing a rotor field, a stator, and one or more stator windings. A D.C. source is provided along with electrically controllable power transistor switch means between said source and each of the windings. A position sensing coil element is mounted adjacent the rotor and has a core which is saturatable by the rotor field at a predetermined position of the rotor to provide a control signal. A control unit is disposed between the means and each of the switches for receiving the control signal and actuating each of the switches in turn in response thereto. The core is preferably ferrite and preferably a permanent magnet.