General Electric Company

Istvan Somos

Dante E Piccone

Donald M Demarest

Angelo L DeCecco

An overvoltage responsive triggering circuit for a main high power thyristor comprises a plurality of n auxiliary thyristors and electric energy storing means connected in series across said main thyristor. The auxiliary thyristors are poled to conduct forward current in the same direction as said main thyristor and have an aggregate forward breakdown voltage greater than a predetermined threshold magnitude. Said threshold magnitude is greater than the aggregate forward voltage of said n auxiliary thyristors minus the forward breakdown voltage of one of said auxiliary thyristors. Between the anode and another electrode of said one auxiliary thyristor there is connected secondary voltage breakdown means having a blocking voltage less than the forward breakdown voltage of said one auxiliary thyristor, whereby said triggering circuit becomes conductive in the breakdown mode at said threshold voltage magnitude.

Adjustable overvoltage protected circuit for high power thyristors

A circuit for controlling the reverse recovery current in a controlled rectifier. The primary winding of a saturable reactor is connected in series with the controlled rectifier. A diode in parallel with a resistor is connected in circuit with the secondary winding of the saturable reactor. The diode is poled to provide a low impedance in the reactor secondary when current flows through the primary winding and through the forward direction of the controlled rectifier. The reverse recovery current of the controlled rectifier flowing through the primary winding of the reactor causes current in the secondary winding to flow in the reverse direction of the diode. The value of the resistor as reflected into the saturable reactor primary circuit limits the magnitude of the reverse recovery current.

Circuit for controlling the reverse current in a controlled rectifier

A thyristor is shunted by a metal oxide varistor in series with switching means which switches abruptly from a normal high-resistance state to a low-resistance, current conducting state when the thyristor is subjected to a transient surge of reverse bias voltage the magnitude of which is higher than a predetermined repetitive peak magnitude and is nearly equal to the level at which the thyristor turns on in an avalanche breakdown mode. The voltage-current characteristic of the varistor is coordinated with the reverse breakdown characteristic of the thyristor so that surge current will divide therebetween in such proportions that the maximum reverse current flowing through the thyristor is lower than a predetermined critical magnitude which can damage the same, whereby the thyristor is able safely to participate in the surge-energy dissipating process.

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Lansdowne, PA, United States of America

Istvan Somos