METHOD AND DEVICE FOR WELDING BY MEANS OF A NON-CONSUMABLE ELECTRODE

The invention relates to a method and a device (1) for welding by means of a non-consumable electrode (2), wherein a welding current (I) alternating in polarity at a welding frequency (fS) is applied by a current source (3) between the electrode (2) and a workpiece (4) in order to form an arc (5), and the polarity is changed back to the polarity before the polarity change if the voltage (U) is above the voltage threshold value (US+, US−) and the welding current (I) is below the current threshold value (IS+, IS−). According to the invention, the welding voltage (U) and the welding current (I) after a preset duration (Δt) after the polarity change are compared with the voltage threshold value (US+, US−) and the current threshold value (IS+, IS−), and in addition the power (P) in the arc (5) is determined, and the polarity is changed back if the welding voltage (U) is greater than the voltage threshold value (US+, US−), and/or if the welding current (I) is less than the current threshold value (IS+, IS−), and/or the determined power (P) is less than a preset power threshold value (PS).