CHARACTERISTICS OF " SCR "

 OBJECTIVES:-

To obtain the V - I characteristics of SCR in a forward bias direction. 

THEORY:-

 The thyristor is 4 layers ( P - N - P - N ), and 3 terminal devices are used in many high power applications. The 3 terminals are known as anode, cathode and gate. When a voltage is applied across anode and cathode with the anode positive thyristor is forward biased, as this voltage has increased the current is very small till break over voltage is reached after this value of forwarding voltage the thyristor starts conduction and behaves like a closed switch the voltage drop across the thyristor is very small. When a positive voltage is applied to the gate, the thyristor starts conducting at a low value of forwarding voltage thus the break over voltage decreases with increases in gate current.

 APPARATUS REQUIRED:-

S.No	Apparatus	Specification	Quantity
1	Ammeter	0-10mA	1 No
2	Ammeter	0-20mA	1 No
3	Voltmeter	0-30 V	1 No
4	Voltmeter	0-20 V	2 No

PROCEDURE:-

 1. Give the connections as per the circuit diagram.

2. Obtain the gate current Ig = 1.5mA by increasing the variable rheostat 

3. Now note down the anode current and anode voltage by varying the RPS.

4. Observe the break over voltage, also holding current and latching current. 

Result: - 

obtained VI characteristics of SCR in forwarding bias. 

Observation Table:-

Ig =1.5mA

S.No	VAK	IAK
1
2
3
4
5
6