Study of V-I characteristics of a given SCR.

Experiment No.: – 1

Aim of the Experiment: –

Study of V-I characteristics of a given SCR.

Apparatus Required: –

Sl. No.NameSpecificationQuantity
1SCR1 no.
2Variable Resistors2 nos.
3Multimeter2 nos.
4Variable D.C Source 15V2 nos.
5Patch CordPVC Insulated CoperAs per Required
Table No. 1.1

Circuit Diagram: –

Figure 1.1 : Circuit Diagram for V-I characteristics of SCR.

Figure 1.2 : V-I characteristics of SCR.

Theory: –

Silicon Controlled Rectifier has built-in features for internal regeneration and has two stable states:

  1. Blocking state
  2. Conducting state

The device can be brought from blocking state to conducting state at any voltage with the help of gate drive. This property is known as switching. The device has the following features:

  1. It is a solid state semiconductor device.
  2. It is compact.
  3. It has low turn-on and turn-off time.
  4. It has negligible losses.

Because of these desirable features the device is used for number of power control applications.

Procedures: –

  1. Connect the circuit as shown in above figure.
  2. Keep the switch S2 open and R1, R2 to high resistance position.
  3. Adjust the variable DC supply to 50 volts.
  4. Measure the voltage across SCR with the help of 150V voltmeter.
  5. Close the switch S2 and adjust R2 to such a value that SCR is brought to ON state. Note gate current required to turn-on SCR.
  6. Note the current passing through SCR and voltage across SCR with 10V voltmeter.
  7. Adjust R1 to a lower value i.e. increases the current to 1 Ampere and note the value of voltage across SCR.
  8. Repeat the above for current through SCR of the value 2 amps, 2.5 amps, 3 amps and 3.5 amps.
  9. Plot V-I characteristics of SCR.
  10. Study the effect of gate current on V-I characteristics. For this open S1. Adjust the supply voltage to 100 volts. Now close switch S1 and find the gate current required to turn on the SCR. Repeat this for supply voltages 150 and 200 volts.

Observation Table: –

Sl. No.Applied voltage (V in volt)Ig – Gate current (mA)Il – load current (Amp)Vt – Voltage after triggering (volt)
1
 2    
 3    
 4    
 5    
 6    
Table No. 1.2

Conclusion: –

To be written by student.

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