Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Experiment No. 5

R-C Triggering TRIAC Circuit Objectives:

1. To analyze RC- firing network of TRIAC.

Equipment: AC supply, oscilloscope, TRIAC (BT136), DIAC DB3, Filament Lamp less than 25W/AC Load, variable gate resistance, connecting wires and breadboard. Circuit Diagram:

Figure 5a

Task: Vary the firing angle (0 to 180 degree) by changing the gate resistance and observe load voltage and voltage across TRIAC on the oscilloscope. Sketch waveforms for selected values of firing angle. Precautions:

1. Should be careful during experiment. 2. Remove voltage signal while patching circuit or making connections. 3. Only connect Voltage signal when it is needed to analyze the circuit. 4. Handle the connections carefully, as you are working with 220V now. 5. Set the probe to 10x.

Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Design Procedure: The design equations are same as used in earlier experiment of R/R-C-triggering.

• Rmin = ______________________ ohms • Gate resistance = ______________ohms

Procedure:

1. It is strictly recommended to observe precautionary measures when dealing with 220 V

voltage signal.

2. Arrange the circuit as shown in Figure 5a.

3. Keep the potentiometer resistance RG to its maximum value so IG is very small and

TRIAC is not triggered. Measure and observe the voltage across load and TRIAC.

4. Observe voltage signals on 10x probe and apply correction in readings.

5. Decrease the resistance of potentiometer RG such that TRIAC is now fired and almost all

the input voltage appears across the load. Measure and observe the change in voltage

across load and TRIAC

6. Record your observations for at least ten different firing angles over the entire range of

observation.

7. Record your observations and calculations in tabular form and also plot the waveforms

observed on oscilloscope.

8. Compare the practical output voltage with theoretical output voltage.

Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Observation Table

No. Firing Angle α Vo (rms)

(Practically using DMM)

Vo (rms)

(Theoretically using

calculations)

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Sketch voltage waveform across load resistance for firing angle in reading 2

Sketch voltage waveform across TRIAC for firing angle used above

Sketch voltage waveform across load resistance for firing angle in reading 4

Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Sketch voltage waveform across TRIAC for firing angle used above

Sketch voltage waveform across load resistance for firing angle in reading 6

Sketch voltage waveform across TRIAC for firing angle used above

Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Show your calculations for voltage with firing angle in reading 3

Show your calculations for voltage with firing angle in reading 7

Sketch the variation of output voltage with firing angle.

Sketch Characteristics of TRIAC

Experiment 5 Registration No. ________________

Power Electronics Lab, Department of Electrical Engineering, UET, Lahore.

Name some applications of the TRIAC

Comments:

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Assignments

1. Simulate the circuit in MultiSim/Orcad and attach the circuit diagram and waveforms

with this manual.

2. What is snubber circuit? Design RC network Snubber Circuit for this circuit. And Show

your Calculations.