A protection circuit for protecting the thyristors of a series circuit of several thyristors, each of which has a corresponding firing circuit to which its anode-cathode voltage is applied. The protection circuit comprises: a plurality of first monitoring means, each of which first monitoring means is associated with and at the potential of a different one of said thyristors, and each of which monitoring means generates a first switching signal when either the current carried by its associated thyristor becomes zero or the voltage across its respective thyristor falls below a predetermined negative value; a plurality of first potential-separating transmission means, each of which first transmission means transmits a different one of said first switching signals; an evaluating means; a plurality of second, potential separating transmission means; a plurality of second monitoring means, each of which second monitoring means is associated with and at the potential of a different one of said thyristors, and each of which second monitoring means generates a second switching signal when the voltage across its associated thyristor exceeds a predetermined positive value; and a plurality of logic circuit means each of which is adapted to feed a signal to the firing circuit associated with a different one of said thyristors when the second switching signal generated by the second monitoring means associated with that one thyristor appears during the timing signal transmitted by the second transmission means associated with that one thyristor.

Protection circuit for serially connected thyristors

Power converter with a failure detector of a self-turn-off semiconductor element

A gate controlling apparatus for a thyristor valve including a plurality of series connected thyristors controlled by a narrow gate pulse. The apparatus includes means for judging whether the thyristor valve is to be in the conductive state or not, means for detecting a forward voltage across at least one of the thyristors in the thyristor valve, and an AND circuit for generating an output at a time when an AND condition between the respective outputs of the judging means and the forward voltage detector means is satisfied. The apparatus further includes means for detecting a period of inverse voltage across at least one of the thyristors in the thyristor valve. The forward and inverse voltages may be, respectively, detected by detecting the forward and inverse voltages of specified thyristors.

Gate controlling apparatus for a thyristor valve

A protection circuit is provided which digitally detects the presence/absence of individual forward voltages across all thyristors at a level low enough compared to the allowable voltage, judges a partial turn-off in accordance with the number of detection signals indicative of the presence/absence, and determines simultaneous firing protection of all the thyristors in accordance with the result of the judgement.

Protection circuit for a thyristor converter

A fault detector apparatus for a power converter in which a plurality of GTOs, functioning at a predetermined potential, are used. The apparatus includes a first fault-detecting circuit, coupled to the gate-cathode path of one of the GTOs, for generating a first fault signal when this GTO malfunctions, a second fault-detecting circuit, coupled to the gate-cathode path of another one of the GTOs, for generating a second fault signal when this GTO malfunctions, a photocoupler for transmitting a DC-isolated optical signal corresponding to the first fault signal, and one optical fiber system for transmitting a DC-isolated output signal, corresponding to the logical sum of the optical signal transmitted by the photocoupler and the second fault signal, to external circuits set at a potential different from the potential at which the GTOs are arranged. The fault-detecting circuits are provided in the same number as the GTOs. The fault-detecting circuits are coupled by the optical signals.

Fault detector apparatus having serial fault-detection signal path

A thyristor rectifier for high voltages includes a number of seriesconnected thyristors each of which has a control device. A control circuit for the whole rectifier includes a control pulse transmitter and a signal emitter for each thyristor which emits an indicating signal when the voltage in the conducting direction of the relevant thyristor reaches a predetermined value. The control circuit includes an input circuit to which signals for ignition of the whole thyristor rectifier are connected. The signal emitters and input circuit are connected to an AND-gate. The different signal emitters are connected to the AND-gate by an OR-gate. The OR-gate is connected to the AND-gate by a flip-flop and the output side of the AND-gate is connected to the flip-flop in such a way that a signal from the OR-gate energizes the flip-flop while a signal from the AND-gate switches it off.

Juhlin Lars-Erik

Papers

Control circuit for a thyristor rectifier

Steuerkreis fuer hochspannungsthyristorventil