SCR Characteristics
Circuit used to plot characteristics of SCR is shown in diagram.
Procedure:-
Make circuit connections as shown in the diagram 1 using patch cords.
1- To plot the V-I characteristics proceed as follows.
2- Rotate both the potentiometer P1 and P2 in fully counter clockwise direction, 3- connect voltmeter to point ‘6’ & ground to read VG and at point ‘3’ & ground to read VAK.
Connect ammeter at point ‘1’ & ‘2’ to indicate the current IA and at point ‘4’ & ‘5’ to indicate the gate current IG.
4- Switch on the power supply.
5- Vary potentiometer P2 to set the gate current IG to a lower value (5.6 mA, 5.7 mA, 5.8 mA).
6- Increase anode voltage VA gradually by varying potentiometer P1.
7- Observe the current IA in the anode circuit. It shows almost zero current at the initial stage.
8- At certain point of positive anode voltage current IA shows sudden rise in reading & voltmeter reading falls down to almost zero. This action indicates the firing of SCR.
9- If this not happens, repeat the procedure from step 5 for slightly higher value of gate current IG.
10- Try the various value of gate current to get the firing of SCR.
11- Keeping gate current constant observe precisely the firing voltage of SCR and record it in the observation table.
12- Also record the anode voltage VA & anode current after firing of the SCR.
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