Device for regulating the welding current during spot welding, having a measurement transmitter, which operates using the root mean square method, for rapid detection of the actual value of the resistance between the electrodes

摘要

The device contains a filter (F1) in which the time-domain waveform of the welding current (I) is supplied to a first root mean square filter (EWF1), and the time-domain waveform of the welding voltage (U) is supplied to a second root mean square value filter (EWF2). The output signals from the root mean square value filters are supplied to means (RE1, RE2) which use this information to derive, by division, the value of the electrical resistance (Rabs, Rswf) of the material to be welded. With the assistance of the resistance value, a regulating device (SW) forms a control signal (W) for the welding current (I), so that spot welds are produced with at least the desired size. The invention has the advantage that a quasi-continuous value for the electrical resistance is obtained irrespective of whether the root mean square value filters (EWF1, EWF2) are of analogue or digital design, so that the regulation quality of the regulating device (SW) is improved. <IMAGE>