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US 4,042,865 AGranted
Separately excited D.C. motors
AssigneeSevcon Limited
InventorDavid Gurwicz
Life of this patent
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AssigneeSevcon Limited
InventorDavid Gurwicz
Estimating the term…
A separately excited speed-controlled D.C. motor which has constant armature current and pulse-controlled field current has its armature connected by way of a bridge rectifier and an inductor to an A.C. source of substantially greater r.m.s. voltage than the rated supply voltage of the armature, the inductor serving to regulate the armature current. The field winding is connected to a field excitation supply and to a thyristor chopper and the mean current through the field winding controlled by the thyristor chopper thereby to control the armature torque and therefore the speed. The field winding may comprise two field coils arranged to produce opposing magnetic fields, the thyristor chopper serving to control the net magnitude and direction of the motor field. A thyristor chopper may be provided in the armature circuit to maintain a constant armature current during plugging of the motor.
A separately excited speed controlled D.C. motor having an armature, regulator means connected to the armature and including voltage-dropping means to permit connection of the armature with a source of supply voltage substantially greater in magnitude than the rated supply voltage of the armature and to maintain the armature current at a substantially constant level during such connection, a field winding, and controllable static switching means connected to the field winding and operable to vary the current through the field winding when the field winding is connected with the supply voltage source or other source of excitation, thereby to control the armature torque and therefore the speed in dependence on the magnitude of the current in the field winding.
Dependencies are inferred from the claim text.