Selco Genesis 90, Repair Manual

Page: 16 / 47

16 Operating principle - Block diagram
Quasi-resonant full bridge power inverter
- 30kHz switching frequency*
= Fast response welding current loop
= High stability welding arc
- ZVS/ZCS for power switches (IGBTs)
= Improved effi lower EMI
= Space saving (high power density)
= Low weight (high power density)
- Primary overcurrent fast protection circuit
- Auixiliary power supplies switching frequency derived from
inverter logic
= System synchronization for noiseless welding arc
(audible subarmonic frequency generation avoided in wel-
ding arc)
* Note: due to resonant topology of primary power inverter,
switching frequency is not constant: it varies in [27 ... 33]kHz
range, depending on actual output power; due to full bridge
topology, secondary rectifier works at double inverter
frquency, that is 55...65kHz, thus allowing a very precise arc
control.