Main components of a circuit

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MAIN COMPONENTS OF CIRCUIT: ã ã ã ã ã ã ã ã ã Delta-wye transformer Phase shifter Zero crossing detector Integrator Comparator Pulse generator Jk flip flop Driver circuit Power circuit WORKING: The three separate identical cards(R,Y,B) are used for controlling the triggered angles of thyristors T1,T2,T3 respectively. The phase shifter shift the phase voltages R’.Y’.B’ in reverse direction. Adjust 100K pots of the phase shifter for shifting the synchronised signal voltages by 60 deg. The output
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  MAIN COMPONENTS OF CIRCUIT : ã Delta-wye transformer  ã Phase shifter  ã Zero crossing detector  ã Integrator  ã Comparator  ã Pulse generator  ã Jk flip flop ã Driver circuit ã Power circuit WORKING : The three separate identical cards(R,Y,B) are used for controlling thetriggered angles of thyristors T1,T2,T3 respectively. The phase shifter shift the phase voltages R’.Y’.B’ in reverse direction. Adjust 100K pots of the phase shifter for shifting the synchronised signal voltages by 60 deg. The output wavesRo,Yo,Bo of the phase shifters are used as synchronised voltages for R,Y,B phases respectively.The zero crossing detector generates square wave pulses(R1,Y1,B1). Thetriangular waves(R2,Y2,B2) are obtained at the output of integrator. Comparator compares the triangular wave forms with a voltage Vc which varies between+Vcc to –Vcc and is controlled by the 47k pot. The output of the comparatorsforms input to the pulse generator(monostable). The monostableoutputs(R4,Y4,B4) are used as a clock pulses for J-K flip flops. Outputs of theflip flops are the required 120 deg conduction pulses for the thyristor.The obtained outputs(R5,Y5,B5) are ANDED with a high frequencycarrying signal to produce the triggered signals. The high frequency is essential toreduce the gate power dissipation and size of pulse transformer.When switch ‘s’ is closed (x=0) the pulse widths are almost same aswaves R5,Y5,B5 respectively. And when switch ‘s’ open (x=1) are almost sameas R5,Y5,B5 if angle less than 60deg. These modified pulse signals are applied tothyristors respectively through pulse transformer. The control circuit is built andtested to give the appropriate gate pulses. It is necessary to check and mark the phase sequence of the power supply and connect properly the phases with the power circuit and control circuit. TEST PROCEDURE : Check whether the firing circuit is working properly or not for allthree phases. If it is working as expected check the polarity of the output pulses of the control circuit. Use proper thyristors and diodes and make three phase half controlled bridge converter power circuit. See that the incoming power supply is properly connected to the bridge and the control circuit so that proper phasesequence is maintained. For safety of power circuit it is routed through properlyrated switch and breaker. Again check the triggered pulses for the thyristor of R,Y,B phases respectively before breaker is switched ON. The triggering pulsesare delivered to the gate of the thyristors.  After connecting the above procedure connect required load andrelease the three phase power supply and firing pulses to thyristors.the circuit willready for operation as a three phase half controlled converter.
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