Abstract: The document specifies a method for fault handling in a converter circuit for switching three voltage levels, in which the converter circuit has a converter subsystem provided for each phase (R,S,T), in which a top fault current path (A) or a bottom fault current path (B) in the converter subsystem is detected, the top fault current path (A) running through the first, second, third and sixth power semiconductor switches in the converter subsystem or through the first and fifth power semiconductor switches (S1, S5) in the converter subsystem, and the bottom fault current path (B) running through the second, third, fourth and fifth power semiconductor switches in the converter subsystem or through the fourth and sixth power semiconductor switches in the converter subsystem, and in which the power semiconductor switches are switched on the basis of a fault switching sequence.

Abstract: The document specifies a method for fault handling in a converter circuit for switching three voltage levels, in which the converter circuit has a converter subsystem provided for each phase (R,S,T), in which a top fault current path (A) or a bottom fault current path (B) in the converter subsystem is detected, the top fault current path (A) running through the first, second, third and sixth power semiconductor switches in the converter subsystem or through the first and fifth power semiconductor switches (S1, S5) in the converter subsystem, and the bottom fault current path (B) running through the second, third, fourth and fifth power semiconductor switches in the converter subsystem or through the fourth and sixth power semiconductor switches in the converter subsystem, and in which the power semiconductor switches are switched on the basis of a fault switching sequence.

Abstract: What is specified is a method for turning off an insulated gate bipolar transistor (IGBT) (1), which is driven by means of a gate electrode driver stage (2) which applies the gate-cathode voltage (UGK) between gate electrode (G) and cathode (K), the anode-cathode voltage of the IGBT (1) being monitored for desaturation and, in the event of desaturation, an acknowledgement signal (SR) being output and fed to the gate electrode driver stage (2).

Abstract: An optical fiber transmission system is specified which can be checked in a simple way for satisfactory power reserve. For this purpose, a transmission current ID is modulated with a frequency fT by switching over the current between a normal value IDN and a smaller test value IDT, which is not equal to zero.

Abstract: A method and a circuit arrangement having a device for measuring the depletion layer temperature of a GTO are specified. In this case, a measurement current (I.sub.M) is impressed in the gate circuit, and the voltage (U.sub.GR) between the cathode and gate is measured, with an applied measurement current (I.sub.M), after the transient turn-off processes have decayed. This voltage (U.sub.GR) is at this time dependent on the depletion layer temperature of the GTO. It thus becomes possible to measure the depletion layer temperature directly on the element, that is to say without circuitous routes via a heat sink temperature and calculation of the thermal resistance or the like, and during operation, continuously, and in consequence to monitor and control the stress level on the GTO precisely.