Electrical supply control for electric arc welding unit - avoids use of mechanical switch in signal circuit and has switch to select direct or alternating current supply

Electric arc welding unit with a switch (U) for selecting direct or alternating current, has, in one design, in addition to two rectifiers (DW1,DW2), the novelty of a third rectifier (DW3) regulated by the control unit (ST). The rectifier has a transformer (T3) whose secondary connection is coupled via a diode (D3) to the secodnary connection of the welding current circuit and whose other secondary connection is linked to the secondary connections of two other transformers (T1,T2). The common secondary connections of all three transformers are joined to the cathode of the third diode rectifier (D3) via electronic switches (F1,F2). ADVANTAGE - The use of a mechanical switch with its inherent disadvantges, in the signal circuit is avoided.