Self-commutating inverter means

Claim 1

In a self-commutating inverter having a pair of main thyristors connected in series with each other and to a d-c source, commutating means comprising a capacitor energy storage means connected between a center tap on the d-c source and a pair of auxiliary thyristors connected anti-parallel to each other, the other ends of said pair of auxiliary thyristors being connected to a common point between said main thyristors, a load connected between the center tap of said d-c source and the connection of said two main thyristors, means to adjust the firing of the transistor in response to varying operating conditions comprising firing control means having outputs which are connected to the main and auxiliary thyristors to trigger said thyristors with firing pulses at presettable times whereby the auxiliary thyristor connected as the commutation valve with a main thyristor is triggered prior to the firing of the main thyristors by a presettable time interval, comprising a first voltage measuring device connected across the capacitor by means of which the actual-value signal of the capacitor voltage is determined, first comparison means connected to said first voltage measuring means to compare the actual-value signal to a reference signal, second and third comparison means for comparing reference and actual signals of the d-c supply voltage and the load current, and summing means connected to said comparison means for summing the difference between actual value-reference capacitor voltages, d-c source voltages and the load current, said firing control means being connected to said comparison means whereby the firing time intervals can be adjusted by said firing control means, as a function of the difference between reference signals and the actual measured signals.