CHARACTRISTICS OF SCR AND ITS APPLICATION
15:20:00
AIM
To plot the V-I charactistics of the given scr.
COMPONENT REQUIRED
1) Thyristor
2) Potentiometer
3) Ammeter :(0-5)mA ;(0-250)µA
4) Rheostat : 200Ω
5) Dc variable voltage power supply (0-30)V - 2nos
6) Diode
7) Voltmeter (0-30)MC
PRINCIPLE
Thyristor is a four layer, three junction PN-PN semiconductor switching device.It has three terminals anode,cathod and gate.A thyristor has three biase mode of operation, namely reverse biasing,forward biasing mode and forward conduction mode (on state mode). When anode is positive with respect to cathode with gate circuit is open, thyrister is said to be forward biased. Then junction J1,J3 are forward biased but junction J2 is reverse biased. In this mode a small current called forward leakage current flows through the SCR. As the forward voltage high, leakage current is small SCR offer a high impedance. A thyrister can be treated as an open switch even in the forward bloking mode.
When anode to cathode forward voltage is increased with gate circuit open, reverse biased junction J2 will have an avalanche breakdown. At voltage called forward beake over voltage Vb0 .after this breakdown thyrister gets turned on and it will be in forward conduction mode. A thyrister can be brought from forward bloking mode to forward conduction mode by turning it on by applying
(a) Positive gate pulse between gate and cathode
(b)a forward breakdown voltage across anod and cathode
PROCEDURE
1. Make the connections as per the circuit diagram.Switch on the supply
2. Set the gate current at the fixed value by varying R0 at gate cathode side.
3. Set the gate current at fixed value, measure the voltage applied anode-cathode side from zero until avalanche breakdown occur.
4. Note down the break down voltage
5. Draw the graph between anode to cathode voltage (VAK ) and anode current Ia
RESULT
Plotted V-I characteristics of scr .
AIM
To plot the V-I charactistics of the given scr.
COMPONENT REQUIRED
1) Thyristor
2) Potentiometer
3) Ammeter :(0-5)mA ;(0-250)µA
4) Rheostat : 200Ω
5) Dc variable voltage power supply (0-30)V - 2nos
6) Diode
7) Voltmeter (0-30)MC
PRINCIPLE
Thyristor is a four layer, three junction PN-PN semiconductor switching device.It has three terminals anode,cathod and gate.A thyristor has three biase mode of operation, namely reverse biasing,forward biasing mode and forward conduction mode (on state mode). When anode is positive with respect to cathode with gate circuit is open, thyrister is said to be forward biased. Then junction J1,J3 are forward biased but junction J2 is reverse biased. In this mode a small current called forward leakage current flows through the SCR. As the forward voltage high, leakage current is small SCR offer a high impedance. A thyrister can be treated as an open switch even in the forward bloking mode.
When anode to cathode forward voltage is increased with gate circuit open, reverse biased junction J2 will have an avalanche breakdown. At voltage called forward beake over voltage Vb0 .after this breakdown thyrister gets turned on and it will be in forward conduction mode. A thyrister can be brought from forward bloking mode to forward conduction mode by turning it on by applying
(a) Positive gate pulse between gate and cathode
(b)a forward breakdown voltage across anod and cathode
PROCEDURE
1. Make the connections as per the circuit diagram.Switch on the supply
2. Set the gate current at the fixed value by varying R0 at gate cathode side.
3. Set the gate current at fixed value, measure the voltage applied anode-cathode side from zero until avalanche breakdown occur.
4. Note down the break down voltage
5. Draw the graph between anode to cathode voltage (VAK ) and anode current Ia
RESULT
Plotted V-I characteristics of scr .
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