Electrical machines

Details Electrical machines Electrical machines

2005-02-01

2005-02-01

Nappi, Hobert (Department: 2837)

Electricity: motive power systems

Induction motor systems

C318S254100

Reexamination Certificate

active

06850029

ABSTRACT:
An electrical machine comprises a rotor without windings, a stator having an armature winding24, 25and a field winding10for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electronic circuit40is provided for controlling the current in the armature winding24, 25such 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 dependent on the speed of rotation of the rotor. Furthermore a control system32supplies control signals to the circuit40to control the current in the armature winding24, 25.In order to enhance the performance at high speed, the control signals are produced in response to sensor output signals which provide an advanced indication of the rotational position of the rotor. Furthermore, in order to prevent oscillation of the rotor on start-up, the control signals supplied to the circuit40during an initial start-up period are each produced after a time delay as compared with the production of the control signals over subsequent cycles of rotation during acceleration of the rotor. This can 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.

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