SELECTIVE CONTROL CIRCUIT FOR THE TIRISTORS OF A DRIVEN THREE PHASES RECTIFYING BRIDGE

The selective ordering circuit for the thyristors of a controlled triphase rectifying bridge is designed for the supply of the reactor of a plant for ionic nitration, in series with an pulse generating circuit for thyristors turning-on and the final amplifier; it allows for the possibility select a variable number of control pulses and to obtain a rectified voltage with a variable number of pulses, between one and eight normal successive pulses at the exit on a controlled bridge. The circuit consists of a logical gate OR-NO (CL1), with six inputs, to which the impulses are applied at the output from the power unit of the rectifier, a binary counter with three grades receiving at the input the output signal of the OR circuit, a combinatorial logic circuit (CLC), consisting of OR and AND parts, which receive at the input the outputs from the counter and a logical selection "word" (8 bits) generated by a switch (K1) with eight positions, having its slide connected to plus, and the contacts, each by means of a resistance connected to the mass, giving at the output a validation signal of variable duration, as per the position of the switch input, and six gates AND (CL15 and CL20), with two inputs, while on one of the inputs the signal with variable duration is applied, and on the other input, the control signal from the control block of the corresponding thyristor.