A fault in a gate turn-off thyristor (GTO) or a bipolar transistor is determined within the circuit, before an anode-cathode (collector-emitter) voltage is applied, by generating a gate pulse and monitoring the resultant gate (base) current. A fault in a gate turn-off thyristor almost always results in a short circuit between the gate-cathode terminals and between the anode-cathode terminals. The gate terminal can be interrupted in the case of other faults (idling state). The base-emitter path of a bipolar device can become faulty in a similar manner. Thus, the gate current which results from a gate pulse becomes abnormally large when the gate-cathode (base-emitter) terminals are short-circuited or the current is zero for an interrupted circuit or for a gate driver fault.

Device and method for testing controllable gate turn-off semiconductors for faults

The invention relates to operation in the field of natural commutation in the case of a bridge circuit having switches which can be turned off. During commutation of an applied current from the emitting switch to a switch of a bridge half which is taking over the current, in order to avoid a reaction reverse current in the emitting switch generating an overvoltage in the reverse direction via the inductances of the valve circuitry it is provided that the emitting switch initially be switched off via the control input of the valve and that the switch taking over the current not be switched on until virtually no current is flowing through the emitting valve. In the meantime, the current can commutate on the valve circuitry of the emitting valve and generate a positive voltage there, so that a reverse current and its hazardous consequences can virtually be avoided. … …

Process and device for the commutation of current between turn-off switches of a current rectifier

The control circuit includes a pair of switching circuits 14, 16 which measure the anode-cathode voltage and the current flowing through respective control thyristors 22, 24 of the inverter thereby to inhibit a gate control signal responsive to an on-off command signal when (i) the anode-cathode voltage falls below a predetermined value, (ii) the current flowing through the thyristor exceeds a predetermined unsafe level, or (iii) upon the occurrence of an inadequate power supply to the gate by circuits. The turn-off and turn-on delay periods of the thyristors may be complementary in duration thereby to assure complete turn-off of one thyristor before a second thyristor conducts in order to decrease the likelihood of short circuits across the poled thyristors. When the gate control triggering signal is inhibited in response to one of the detected unsafe conditions, the gate driver inhibit is preferably sustained for a duration to allow normal turn-off in response to the on-off command signal thereby to permit re- initialization of the power circuits of the gate driver. Also, sustaining of the inhibit condition permits sufficient time for a master control device to recognize the detection of the unsafe condition and to alter its state of operation accordingly.

Switching Control Circuit for DC/AC Inverter

ACIRCUIT DE COMMANDE DE COMMUTATION POUR UN INVERSEUR CONTINUALTERNATIF BCIRCUIT CARACTERISE EN CE QUE CHAQUE MOYEN-REDRESSEUR COMPORTANT UN MOYEN A PORTE 14, 16 REPONDANT A L'ARRIVEE D'UN SIGNAL DE DECLENCHEMENT 19 POUR EN ASSURER LA CONDUCTION AINSI QU'A L'ABSENCE DE SIGNAL DE DECLENCHEMENT 19 POUR ARRETER LA CONDUCTION, UN PREMIER ET UN SECOND MOYEN DE COMMANDE ASSOCIES RESPECTIVEMENT AU PREMIER ET AU SECOND MOYEN DE REDRESSEMENT POUR COMMANDER L'OBTENTION DES SIGNAUX DE DECLENCHEMENT RESPECTIFS EN REPONSE A UN SIGNAL D'ORDRE BRANCHEMENTCOUPURE CL'INVENTION CONCERNE UN CIRCUIT DE COMMANDE SUSCEPTIBLE D'ETRE RELIE A UNE SOURCE D'ALIMENTATION POUR UN CIRCUIT-INVERSEUR DE MOTEUR A COURANT ALTERNATIF

Kernick Andress

Papers

Switching Control Circuit for DC/AC Inverter

Circuit de commande de commutation pour un inverseur continu/alternatif