Abstract: A method for operating an inverter (1) of a photovoltaic installation is specified, wherein a reference value/reference profile of at least one parameter of the photovoltaic installation is compared with an actual value/actual profile of said parameter. If the deviation between said actual value/actual profile and the reference value/reference profile exceeds a predefinable threshold, then the inverter function of the inverter (1) is at least temporarily disabled. Furthermore, an inverter (1) for carrying out said method is specified.

Abstract: A method for controlling and/or regulating a welding apparatus with a welding wire, wherein after ignition of an electric arc, a cold metal transfer welding process is conducted. For creating more various possibilities for controlling heat introduction into the work piece and/or for introducing filler material, it is provided that during at least some short-circuit phases, polarity of the welding current I and/or the welding voltage U is switched, wherein the amplitude of the welding current I and/or the welding voltage U is adjusted to a defined value so that melting-through of the welding wire and the short-circuit bridge, respectively, is prevented. There is also a safe re-ignition of the electric arc when lifting the welding wire off the work piece. It is also possible to reignite the electric arc only by the welding current I and/or the welding voltage U without any auxiliary voltage, at the end of the short-circuit phase or at the beginning of the electric-arc phase.

Abstract: The invention relates to a method for controlling and/or regulating a welding apparatus (1) with a welding wire (13), wherein after ignition of an electric arc (15), a cold metal transfer welding process is conducted, as well as to a welding apparatus (1) for conducting the method.