Welding inverter and method for controlling a welding inverter

Abstract

The present invention concerns a half-bridge inverter and a method for controlling such a welding inverter which has a nominal output power P.sub.n and a nominal operating angular frequency .omega..sub.t, the inverter being comprised of a DC power source (E); of a capacitor configuration comprising at least one capacitor (C.sub.n), the circuit being connected at its first end to one end of the DC power source (E) and at its other end to a point A; of two switching elements (T.sub.1, T.sub.2) connected in series over the DC power supply (E), the switching elements being capable of controlling the pulse width .tau. of the current to the welding load, and thus the power to the welding load, whereby .tau..sub.max determines the nominal power output of the inverter; and of a transformer primary (L.sub.p) connected at its first end to point A and at its second end to the center point of the switching elements (T.sub.1, T.sub.2), and the current switched through the primary has a peak value I.sub.i. At output power levels which exceed the critical output power P.sub.k, the total capacitance .SIGMA.C of the capacitor circuit (C.sub.n) is smaller than the product of the current I.sub.i and the pulse width .tau. divided by the voltage E of the DC power source (.SIGMA.C<(I.sub.i .times..tau.)/E), and the resonant angular frequency .omega..sub.r (=1/.sqroot.L.sub.p .tau.C) determined by the total inductance L.sub.p of the transformer primary and the total capacitance of the capacitor configuration (C.sub.n) is essentially lower than the operating angular frequency .omega..sub.t of the inverter.