Patent ID: 6788020
Filing Date: 2004-09-07
Classification: H02P

Abstract:
An electrical machine comprising a rotor without windings, a stator having an armature winding and field magnet means for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding, circuit means for controlling the current in the armature winding such that periods in which a magnetomotive force in one direction is associated with a first current pulse alternate with periods in which a magnetomotive force in the opposite direction is associated with a second current pulse, and position sensing means for monitoring the rotational position of the rotor and for supplying output signals dependent on the speed of rotation of the rotor, characterised by control means for supplying switching control signals to the circuit means to control the current in the armature winding, such that each switching control signal is produced in response to detection of a respective one of said output signals from the position sensing means and so that the switching on time is maintained for a length of time determined by the duration of said output signal.