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Tuesday, June 28, 2011

DESIGN OF DC VOLTAGE REGULATOR USING SCR


DESIGN OF DC VOLTAGE REGULATOR USING SCR

EXPT NO: 6

AIM:

       To study the operation of DC voltage regulator with R load and observe the waveform.


APPARATUS REQUIRED:
  
  1. Single Phase SCR bridge converter trainer kit.
  2. Patch chords.
  3. CRO


THEORY:

           Rectification is a process of converting an AC to DC. The fully controlled converter uses thyristors as the rectifying elements and the Dc output as function of amplitude of the Ac supply voltage and the point at which the thyristors are triggered. During the positive half cycle of the input voltage SCR 1, SCR 2, are forward biased and are simultaneously triggered at the firing angle a. The supply voltage appears across the load resistance R. The load voltage is 0 from p to p+a, until the SCR 3 and SCR 4 are triggered in negative half cycle. The load current now flows from the supply, SCR 3,Load and SCR 4.thus the direction of current through the load is the same in both half cycles. The output voltage is given by the expression.

                                    V0 = Vm / p (1+cosa) volts



CIRCUIT DIAGRAM:








MODEL GRAPH :


TABULATION:




Firing Angle (a )
Output DC voltage (volts)




















PROCEDURE:

1.      Switch ON the trainer power ON/OFF switch.
2.      Switch ON the 24-volt AC power supply.
3.      Switch ON the debounce logic switch and connect the R load.
4.      Vary the controlled voltage from minimum to maximum.
5.      For each step note down the Firing angle and the output voltage.



RESULT:

             Thus the operation of fully controlled converter with R load has been studied and the waveforms are observed.

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