method for controlling the stromrichterventile of gleichstromseitig series connected parallelschwingkreiswechselrichtern

摘要

A method is proposed for driving the converter valves of two or more load-commutated parallel resonant circuit inverters 5,6,7,8 with one induction furnace in each case which are fed from a common direct-current source and are connected in series on the direct-current side, a current flow from the direct-current source via the parallel resonant circuit connected to an inverter being set by triggering two diagonally opposite converter valves of this inverter in each case. In order to switch off a parallel resonant circuit 9, C 1 , two diagonally opposite converter valves are left on until the load voltage of the parallel resonant circuit 9, C 1 has approximately zero value. At least one further converter valve located in series on the direct-current side with a valve in the on state is then triggered. In order to switch on a parallel resonant circuit, a converter valve of a start device 15 and, in co-ordination therewith, at least one converter valve, in the off state, of the inverter are triggered.