Abstract: An apparatus for a-c welding with a consumable electrode has a welding transformer having a secondary winding connected to an electrode gap and two pulse generators. Each pulse generator has a power circuit connected in parallel with the electrode gap and consisting of a series circuit including a thyristor switch, a power supply winding and a switched capacitor, and a unit for controlling the thyristor switch. Each control unit has a zero detector and a control pulse former, the zero detector of the control unit of the first pulse generator being connected in parallel with the electrode gap, and the zero detector of the control unit of the second pulse generator being connected in parallel with the switched capacitor of the first pulse generator.