High frequency inverter for resistance spot welding applications with increased power cycling capability

Resistance spot welding is a commonly used industrial process. Miniaturization and a demand for higher control precision lead to a higher switching frequency and higher switching losses of the inverter. The pulsed operation of a resistance spot welding power supply decreases module lifetime through power-cycling. This work proposes the use of a passive RC clamp circuit to reduce the switching losses in the IGBTs. The first part of this work explains the commutations and the occurrence of switching losses in a hard-switching and the proposed clamped inverter. The experimentally determined switching losses are presented and the junction temperature ripple is calculated. The effect of the clamping circuit on the magnetization current is described and a digital filter to avoid controller induced transformer saturation is proposed.