Line voltage compensation for AC resistance welding systems and the like

Abstract

An AC line voltage compensation method and controller for use with an AC welding system that is adapted to weld an article. Welding parameters are provided by an operator that are suitable for welding the article. A desired heating percentage is also input by the operator that is determinative of an RMS output voltage supplied by the AC welding system. The AC line voltage supplied to the AC welding system is measured by means of a voltmeter. The difference between the measured AC line voltage and a desired nominal AC line voltage is determined. The time at which heat is applied to the article is adjusted as a function of the measured difference to maintain the RMS output voltage supplied at the output of the AC welding system at a relatively constant level for all AC line voltages supplied to the AC welding system. More specifically, gain adjustment which provides for improved line voltage compensation, and which is controlled by means of a user programmed digital control panel, has been added to a line voltage compensation computational algorithm employed in an AC resistance welding controller. The use of the user programmed gain factor allows an operator to adjust the amount of compensation for a specific welding setup. The user adjusts the gain factor to modify a mathematically calculated term for line voltage compensation. The computed gain factor is used to set a variable time delay, after which an SCR is turned on. The variable time delay determines the phase angle of the AC pulse applied during each weld.

Dependencies are inferred from the claim text.