An inverter system for inductive tube welding utilizing resonance transformation

The following paper presents a tube welding inverter system based on a three-state resonant circuit. The advantages of this resonance transformation approach in comparison to the classical series or parallel resonant schemes are highlighted. The derivation of the resonance transformation circuit is presented together with an easy to use formula for its current transfer ratio. The effect of varying circuit parameters is evaluated. The circuit offers a simple method of connecting inverter modules in parallel. This resonant circuit is driven by a voltage-fed MOSFET inverter. It makes effective use of the parasitic inductances and internal diodes of the power semiconductors. Experimental results demonstrate system efficiency and the immunity of the system against load shorts. Due to the resonant transformation topology, no system shut-down is necessary during load shorts.<
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