Study of  half-wave  Gate Controlled Rectifier Using One SCR.

Experiment No.: 18

Aim of the Experiment: –

Study of  half-wave  Gate Controlled Rectifier Using One SCR.

Objectives: –

  1. To study the operation of a SCR working as a half-wave gate-controlled rectifier.
  2. To observe and verify the effects of varying the gate current on the firing point of a SCR when used as a half-wave rectifier.
  3. To observe and study the waveforms obtained in a half-wave SCR rectifier circuit.
  4. To vary the value of the firing angle of the device and observe the variations in the load voltage.

Apparatus Required: –

Sl. No.NameSpecificationQuantity
1.SCR4A, 600V (TYN 604 or any other equivalent)1 no.
2.Step-down transformer220/12V, 500mA, 50Hz1 no.
3.Diode1.2A, 220V (By 127 or any other equivalent)1 no.
4.Load resistance (R)150Ω, 10W1 no.
5.Limiting resistance50Ω, 2W1 no.
6.Potentiometer (POT)10K-2K(wire wound)1 no.
7.Oscilloscope(0-10 MHz)1 no.
Table No. 18.1

Circuit Diagram: –

fig. 6.1

Theory: –

fig. 6.2

Procedures: –

  1. Make the connections according to the circuit diagram.
  2. Keep the POT at its minimum resistance value and switch ON the a.c. supply.
  3. Observe the pattern of the a.c. input wave on the CRO and measure its frequency.
  4. Observe the pattern of the voltage wave between the anode and the cathode, and watch the variation in firing angle by varying the voltage from minimum to maximum with the help of the POT. Trace the wave pattern.
  5. Repeat step No. 4 for voltage across (i) the gate and the cathode and (ii) the load.
  6. Note down the maximum and the minimum values of firing angle.

Observation: –

  1. Maximum value of firing angle     =  …………. degrees
  2. Minimum value of firing angle     =  …………. degrees

Precautions: –

  1. It should be assured that the gate of the SCR is supplied with a positive signal.
  2. The voltage applied between the anode and the cathode of the SCR must be well below its peak inverse voltage.
  3. The terminals of the SCR should be checked before connecting it in the circuit.

Conclusion: –

To be written by student.

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