EEE-454, Power Electronics Laboratory

Experiment 1

Switching Mechanism of Unidirectional Power Switches

Part 04


4. SCR AS A Switch:


EQUIPMENT:

  1. SCR - [Model: BT 151]
  2. Resistor - [1K].
  3. Ceramic Resistor - [220Ω]
  4. Power Supply - [10V].                                
  5. Connecting Wire.
  6. Multimeter.
  7. Trainer Board.
  8. Variable DC Power Supply.


CIRCUIT DIAGRAM:



Fig. SCR as a switch.


DATA TABLE:


Forward Bias

VGG

I

0.1 V

0 A

1.1 V

0 A

1.5 V

0 A

1.8 V

0 A

1.9 V

29.1 mA (Latching Current)


Reverse Bias

VAA

I

9.99 V

27.6 mA

8.04 V

20.9 mA

7.05 V

16.3 mA

6.05 V

13.1 mA

5.08 V

9.3 mA

4 V

5.7 mA

3 V

2.99 mA

2.99 V

2.0 mA (Holding Current)

2.75 V

0 mA



PRACTICAL WORK:




DISCUSSION: This lab is related to how SCR works as a switch. We can use an SCR as a switch. By using an SCR as a switch, we can automate the process of switching or switching on or off the load remotely operated instead of using an electromechanical switch that is operated by hand. While doing this experiment, we follow all the rules of the laboratory. First of all, we connect all equipment by following a circuit diagram. Then we connect all the equipment with the AC supply for our experiment. The SCR has only two states, namely; ON state and OFF state, and no state in between. When the appropriate gate current is passed, the SCR starts conducting heavily and remains in this position indefinitely even if the gate voltage is removed. This corresponds to the ON condition. However, when the anode current is reduced to the holding current, the SCR is turned OFF. It is clear that the behaviour of SCR is similar to a mechanical switch. As SCR is an electronic device, therefore, it is more appropriate to call it an electronic switch. We take all the values perfectly and put them on the table. We are very careful to take the value of voltages and currents. Sometimes multimeter was not capable to read the short-range value of current. So, we take an effective ammeter to measure the short range of the current value. Finally, we disconnect all the connections carefully and return the equipment to the lab assistant.



PART - 03 CLICK HERE