Procedure of resistance welding in particular with alternating non sinusoidal welding current and arrangement for the working of the procedure

摘要

A procedure is described for resistance welding with, in particular, an alternating welding current pulsating in periodic half waves which is generated from an alternating primary voltage (Up) of a welding transformer (16) and is regulated by pulse duration modulation of this alternating primary voltage. The alternating primary voltage (Up) is n-times chopped in each half wave during the pulse duration modulation, where n 1. In each half wave, the welding current is regulated by the fact that n nominal/actual-value comparisons of the welding current are carried and the duty ratio during the pulse duration modulation is acted upon a corresponding n-times. To regulate the welding current, a regulator (18) is provided which has a memory which contains nominal current values corresponding to the welding current shape for each chopping interval for comparison with each actual current value determined per chopping interval. In this manner, it is not only possible to achieve very short regulating times because the welding current can be corrected several times within each of its halfwaves, but the welding current shape is also freely selectable because a large number of nominal values can be kept ready in the memory for each half wave of the welding current. For electrical resistance welding, a current variation which deviates from the sinusoidal shape is selected in each half wave of the welding current. As a result, energy output to the material to be welded can be accurately metered which makes it possible to weld previously problematic materials such as very thin and/or weakly tinned tin-plate or black-plate, chrome-plated sheet metal and so forth with very good welding quality and high throughput. IMAGE