Apparatus for instantly compensating for line voltage irregularities
AssigneeCombustion Engineering, Inc.
InventorGeorge Robison Madewell
Life of this patent
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Abstract
An apparatus for compensating for line voltage variations in a pulsed welding arc supply. A circuit for drawing a current that is proportional to that part of the supply voltage in excess of a predetermined reference is drawn from the capacitor charging circuit in a UJT triggering device. Thus, the more the line voltage exceeds the desired level, the greater is the compensating current withdrawn from the capacitor charging circuit. As a result, the average welding current remains at the desired level despite supply-voltage variations.
Claims3
In a current control circuit of the type that triggers means for permitting current from a supply voltage when the charge on a capacitor reaches a trigger level, the capacitor being charged by a charging current, at least part of which is caused by a charging-voltage source and a first series resistance in series with the charging-voltage source that are connected across the capacitor, the improvement comprising:
- a. a second series resistance connected in series with the charging-voltage source, the first series resistance, and the capacitor;
- and
- b. means, connected across the second series resistance, thereby forming a loop comprising itself and the second series resistance, and including a second voltage source whose value is essentially proportional to the instantaneous value of a rectified version of the supply voltage, for causing current to flow in the loop.
A method for improving the operation of a current control circuit of the type that triggers a means for permitting current from a supply voltage when the charge on a capacitor reaches a trigger level, the capacitor being charged by a charging current, at least a part of which charging current is caused by a charging circuit connected across the capacitor, which charging circuit includes, in series, a charging-voltage source, a first series resistance, and a second series resistance, the charging-voltage source thereby causing an uncompensated voltage drop across the second series resistance, comprising the step of impressing a compensating voltage across the second series resistance when the compensating voltage exceeds the uncompensated voltage across the second series resistance, the compensating voltage being proportional to the amount by which the supply voltage exceeds a threshold value.
Dependencies are inferred from the claim text.