Performance analysis of full wave controlled Rectifier with R load at different firing angle.

Experiment No.: – 06

Aim of the Experiment: –

Performance analysis of full wave controlled Rectifier with R load at different firing angle.

Objective: – Understand how full wave controlled SCR based converter functions and also it’s associated waveforms.

Apparatus Required: –

Sl. No.NameSpecificationQuantity
1Experimental KitPE trainer with INV/CON panel1 no.
2DSO/CROTwo channel1 no.
3Connecting wirePatch cord
as per required.
4Resistive load100 W bulb.1 no.
5Multimeter/Voltmeter1 no.
Table No. 6.1

Circuit Diagram: –

Fig. 6.1

Theory: –

SCR conducts only when it’s anode is positive w.r.t. cathode and a synchronized gate pulse is applied to it’s gate.

During positive half cycle of input AC, the load circuit can complete it’s path as TH1-Load-TH2-back to supply.

(as anode is positive w.r.t. cathode for both the SCRs) If gate pulse is given at an angle α  (ref waveform fig. 6.2 ) then SCRs will conduct for π-α and voltage appears across load for the period(π-α).

Fig. 6.2

During negative half cycle, TH1 and TH2 are reverse biased but TH3 and TH4 can now conduct keeping the direction of current same in load. Thus unidirectional current flows through loading both the halves of input AC.

We can vary the conduction period of an SCR by varying the firing angle. Using standard integration method as follows one may derive the formula for Average load voltage,

Procedures: –

  1. For this configuration, four SCRs are required from CON/INV panel. The lamp is available on top board. For input AC use 230V AC banana shockets from top board. Use 100W lamp as load.
  2. Make the connections as per circuit diagram given above to form full wave-controlled converter. A 100W/230V lamp from top board should be used for load. All connections should be done using patch cords provided.
  3. The firing pulse selector switch should be kept on 4th position for getting required gate pulses. By doing so you are selecting UJT relaxation oscillator based SCR firing. Now put on Ac mains.
  4. Connect CRO across load and observe the load waveforms. You can also observe change in conduction angle by varying the conduction angle control pot on LSPT panel.
  5. Take the reading as per following table. Use 300V DC meter from top board for this purpose.

Observation Table: –

Sr. No.Firing angle αPeak voltage Vin(mV)Average voltage Vdc
As per formulaOn 300V DC meter
1   
2   
3   
4   
5   
Table No. 6.2

Conclusion: –

Written by student.

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