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US 6,646,406 B1Granted
Electrical machines
AssigneesBlack & Decker Inc., University of Warwick
InventorsCharles Pollock, Helen Geraldine Phyllis Pollock, Richard Thomas Walter
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AssigneesBlack & Decker Inc., University of Warwick
InventorsCharles Pollock, Helen Geraldine Phyllis Pollock, Richard Thomas Walter
Estimating the term…
An electrical machine comprises a rotor without windings, a stator having an armature winding 24, 25 and a field winding 10 for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electronic circuit 40 is provided for controlling the current in the armature winding 24, 25 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. A position sensor is provided for monitoring the rotational position of the rotor and for supplying output signals at a rate dependent on the speed of rotation of the rotor. Furthermore a control system supplies control signals to the circuit 40 to control the current in the armature winding 24, 25 in response to the output signals. The control system uses a control signal of extended duration at the beginning of the first current pulse on start-up of the motor from rest as compared with the duration of the control signals produced over the remainder of the first current pulse during acceleration of the rotor. Such an arrangement produces efficient starting from rest, and enables control of acceleration, no-load speed, loaded torque-speed characteristics of the machine to be achieved with simple on-off control of armature and field switching devices, so that the control circuitry can be produced at relatively low cost. Simplification of the control circuitry is further ensured by the fact that such control can be effected without current sensing.
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 at a rate dependent on the speed of rotation of the rotor, characterised by control means for supplying control signals to the circuit means to control the current in the armature winding in response to said output signals, the control means being arranged to produce a control signal of extended duration at the beginning of the first current pulse on start-up of the rotor from rest as compared with the duration of the control signals produced over the remainder of the first current pulse.
An electrical machine comprising a rotor without windings, a stator having an armature winding and a field winding for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding, the armature and field windings being connected in a series configuration, and circuit means for controlling supply of current to 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, characterised in that a secondary winding is closely coupled to the field winding and is connected in a circuit with rectifying means so that current flow is induced in the secondary winding and the rectifying means by current flow in the field winding in such a manner as to tend to maintain the flux in the field winding substantially constant.
An electrical machine comprising a rotor without windings, a stator having an armature winding and a field winding for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding, the armature and field windings being connected in a series configuration, and circuit means for controlling supply of current to 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, characterised in that the desired field magnetomotive force MMFf is related to the working armature magnetomotive force MMFa by a substantially constant value k.
Dependencies are inferred from the claim text.