Abstract: A device for failure detection in series-connected semiconductor rectifiers (1) comprises transformers (2) whose number is equal to that of the rectifiers (1) and which comprise input windings (3), supply windings (6), and additional parallel-connected windings (9), RC-circuits whose number is equal to that of the rectifiers (1), having resistors (4) and capacitors (5), and also a pulse generator (7), and a measuring element (8).The input winding (3) of each transformer (2) has one lead-out thereof connected to a cathode of the respective rectifier (1), and another lead-out to the capacitor (5) of the respective RC-circuit. The resistors (4) of each RC-circuit are connected to the anodes of each rectifier (1). The supply windings (6) of the transformers (2) are connected to one another in series and connected by one terminal to the first lead-out of the pulse generator (7).