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US 4,399,511 AGranted
Power factor monitoring and control system for resistance welding
AssigneeSquare D Company
InventorDennis J. Jurek
Life of this patent
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AssigneeSquare D Company
InventorDennis J. Jurek
Estimating the term…
A power factor monitoring and control system for controlling the quality of a spot weld made by assembly line welders. The control system of the present invention detects a change in the load power factor as the weld is formed which is manifested as a change in the current extinction angle of the half cycles of weld current. The time interval between the instant weld current is extinguished at the end of a programmed half cycle and an instant when current is extinguished at the end of a subsequent half cycle provides a measure of the resistance across the weld nugget. The time interval information is stored and compared with information provided during a previous half cycle to generate a difference signal. The change in resistance in the secondary circuit is reflected through the transformer to the transformer primary circuit as a decrease in power factor. The timing changes resulting from the decrease in power factor are sensed by the control circuitry to generate signals which operate to selectively vary the weld heat setting of the welder control or terminate the weld current.
A control system for controlling the quality of a weld in a resistance welding apparatus with the apparatus including a pair of welding electrodes and a welding transformer having a secondary winding connected to the electrodes and a primary winding connectible to an AC source for energizing the primary winding and the secondary winding with alternating polarity half cycles of welding current comprising:
A method for controlling the quality of a weld that is formed by a resistance welding apparatus with the apparatus including a pair of welding electrodes engageable with a pair of workpieces that are to be welded together and a welding transformer connected to the electrodes and a primary winding connectible to an AC source for energizing the primary and the secondary winding with alternating polarity half cycles of welding current comprising:
A control system for controlling the quality of a weld as formed in a resistance welding apparatus with the apparatus including a pair of welding electrodes and a welding transformer having a secondary winding connected to the electrodes and a primary winding connectable to an AC source for energizing the primary and the secondary windings with alternating polarity half cycles of welding current comprising:
A control system for controlling the quality of a weld in a resistance welding apparatus with the apparatus including a pair of welding electrodes and a welding transformer having a secondary winding connected to the electrodes and a primary winding connectible to an AC source for energizing the primary winding and the secondary winding with alternating polarity half cycles of welding current comprising:
Dependencies are inferred from the claim text.