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Forced Commutation of SCR


To Study and observe the Forced Commutation of SCR by different methods.

Apparatus Required




CRO Settings

  • Time (X) Axis : 5ms/div
  • Voltage (Y) Axis: 20V/div
  • Probe: 1:10 CRO Probe is suitable one.


Initial Settings

  • Ensure the 230V Power Supply is in proper with Tester.
  • Ensure the CRO is working properly with probe checking and proper ground line axis.


Experiment Steps

  • The connections are made as per the circuit diagram given above.
  • When the load is Rheostat, then it must be in maximum position.
  • Turn on the SW2 and observe the waveform across between G1&K1 and G2&K2. And ensure it is like triggering pulse given in model graph.
  • Turn ON SW1 and observe the waveform across the load.
  • Measure the X-axis time interval of ON time of Load Voltage and OFF Time of Load Voltage.
  • Adjust the value of Firing angle and note down the load voltage
  • Repeat the step 5.
  • Repeat the experiment for different values of α and note down Vo.


Circuit diagram

Class A

Mimic Diagram of Class A

Class B

Mimic Diagram of Class B

Class C

Mimic Diagram of Class C

Class D

Mimic Diagram of Class D

Class E

Mimic Diagram of Class E