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GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
Lab Manual
Of
Industrial Electronics
(3341105)
1
GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
INDEX
Sr.No.
Date
Title
1
To Study characteristics of SCR
2
To Study characteristics of TRAIC
3
To Study characteristics of DAIC
4
To perform phase control of TRIAC
with DIAC.
To perform an UJT synchronized
triggering scheme of SCR
5
6
7
8
9
10
To study the performance &
waveforms of HWR by using RC
triggering Circuit.
To study the performance &
waveforms of FWR by using RC
triggering Circuit
To Implement Squential Timer Using
IC-555.
To Implement Timer Delay Using IC555.
To study the operation of a Synchro
Transmitter (CX) and Synchro receiver
(CR) Connected together.
2
Page
No.
Sign
GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:1
AIM: To study the V-I characteristics of S.C.R.
APPARATUS:
S.C.R , Power Supplies, Wattage Resistors, Ammeter, Voltmeter, etc.
THEORY:
SCR Construction :
A thyristor (or silicon-controlled rectifier) is a pnpn device with three terminals:
1. Anode (A)
2. Cathode (K)
3. Gate (G)
Fig. : Thyristor pnpn construction & Symbol.
When the device is reverse-biased ( VAK <0), no current flows.
When the device is forward-biased ( VAK >0), no current flows until a current pulse is applied
to the gate.
The SCR can be visualised as seperated into two transistors where it can be split into two parts
and displaced mechanically from one another but connected electrically.Thus the device can be
considered to be consitituted of two transistor T1(PNP) and T2(NPN) Connected back to back as
shown in figure.
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IE(3341105)SEM-4
Fig.: Physical Diagram & Equivalent Schematics
Characteristics:
Forward characteristics:
Forward bias characteristics is the curve drawn between forward anode to cathode voltage and
anode current. It is divided into 3 regions



OFF State
Negative resistance
ONState
Fig.:Forward charateristics
Reverse Charateristics:
In Reverse bias,a very small leakage current flows, known as the reverse current .If the reverse
voltage is gradually increased,at some reverse voltage,avalanche breakdown occurs and SCR
start conducting heavily in reversec direction .Many times reverse Breakdown voltage is sightly
higher than forward beakover voltage.
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IE(3341105)SEM-4
Fig.:Reverse Charateristics
CIRCUIT DIAGRAM:
PROCEDURE:
1. Connections are made as shown in the circuit diagram.
2. The value of gate current IG, is set to convenient value by adjusting VGG.
3. By varying the anode- cathode supply voltage VAA gradually in step-by-step, note down
the corresponding values of Vak & Ia. Note down Vak & Ia at the instant of firing of
SCR and after firing (by reducing the voltmeter ranges and increasing the ammeter
ranges) then increase the supply voltage VAA. Note down corresponding values of Vak&
Ia.
4. The point at which SCR fires, gives the value of break over voltage Vbo.
5. A graph of Vak V/S Ia is to be plotted.
6. The on state resistance can be calculated from the graph by using a formula.
7. The gate supply voltage VGG is to be switched off
8. Observe the ammeter reading by reducing the anode-cathode supply voltage VAA. The
point at which the ammeter reading suddenly goes to zero gives the value of Holding
Current IH.
9. Steps No.2, 3, 4, 5, 6, 7, 8 are repeated for another value of the gate current Ig.
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Characterisics curve:
It is the curve between the Anode to Cathode voltage and anode Current.
Observation Table:
` IG =
uA.
Sr No.
CONCLUSION:
6
IE(3341105)SEM-4
GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:2
AIM: To Plot V-I Characteristics of TRIAC.
APPARATUS:
TRIAC – BT 136, power supplies, wattage resistors, ammeter, voltmeter, etc.,
THEORY:
Triac is a three terminal, four layer bilateral semiconductor device. It incorporates two SCRs
connected in inverse parallel with a common gate terminal in a single chip device. As seen, it has
six doped regions. The gate terminal G makes ohmic contacts with both the N and P materials.
This permits trigger pulse of either polarity to start conduction. Since the triac is a bilateral
device, the term “anode” and ”cathode” has no meaning, and therefore, terminals are designated
as main terminal 1. (MT1), main terminal 2 (MT2) and gate G. It can be imagined from the
circuit symbol that the triac consists of two thyristors back to back. The operation of the triac can
be looked on in this fashion, although the actual operation at the semiconductor level is rather
complicated. When the voltage on the MT1 is positive with regard to MT2 and a positive gate
voltage is applied, one of the SCRs conducts. When the voltage is reversed and a negative
voltage is applied to the gate, the other SCR conducts. This is provided that there is sufficient
voltage across the device to enable a minimum holding current to flow.
Fig.: Symbol & Schemetic Diagram.
Construction:
The structure of a triac may be considered as a p-n-p-n structure and the triac may be considered
to consist of two conventional SCRs fabricated in an inverse parallel configuration.
In operation, when terminal A2 is positive with respect to A1, then a positive gate voltage will
give rise to a current that will trigger the part of the triac consisting of p1 n1 p2 n2 and it will
have an identical characteristic to an SCR. When terminal A2 is negative with respect to A1 a
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IE(3341105)SEM-4
negative current will trigger the part of the triac consisting of p2 n1 p1 n3. In this way
conduction on the triac occurs over both halves an alternating cycle.
Fig.: Structure of traic.
Characteristics:
The triac has on and off state characteristics similar to SCR but now the characteristic is
applicable to both positive and negative voltages. This is expected because triac consists of two
SCRs connected in parallel but opposite in directions. MT2 is positive with respect to MTX in
the first quadrant and it is negative in the third quadrant.
Quadrant I operation
:
VMT2, positive; VG1 positive
Quadrant II operation
:
VMT21 positive; VGl negative
Quadrant III operation :
VMT21 negative; VGl negative
Quadrant IV operation :
VMT21 negative; VG1 positive
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IE(3341105)SEM-4
CIRCUIT DIAGRAM:
Fig.: Forward Bias
Fig.: Reverse Bias
PROCEDURE:
1.
2.
3.
4.
5.
6.
The connections are made as shown in the circuit diagram.
The TRIAC is connected in forward direction and supply is switched ‘ON’.
VMT1MT2 is constant by varying RPS2 and then varying IG by varying RPS1.
The corresponding ammeter and voltmeter readings are noted and tabulated.
Next the TRIAC is connected in reverse direction.
The above process is repeated.
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IE(3341105)SEM-4
Characteristics curve:
OBSERVATION TABLE:


MT2- Positive & MT1-Negative.
IG =
Sr. No.
Vm1m2
I Traic
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

EC DEPARTMENT
IE(3341105)SEM-4
MT2- Negative & MT1-Positive.
IG =
Sr. No.
Vm1m2
I Traic
CONCLUSION:
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EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:3
AIM: To Plot Characteristics of Diac.
APPARATUS:
Diac, Power Supplies, Wattage Resistors, Ammeter, Voltmeter, etc.,
THEORY:
The diac is basically a two terminal parellel-inverse combination of semiconductor layers that
permits triggering in either direction. The basic arrangement of the semiconductor layers of the
diac is shown in the figure, along with its graphical symbol. Nore that either terminal is referred
as the cathode. Instead, there is an anode 1 and an anode 2.
Fig.: Symbol & Construction
Characteristics:
CIRCUIT DIAGRAM:
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EC DEPARTMENT
IE(3341105)SEM-4
Fig.: Forward Bias.
Fig.:Reverse Bias.
PROCEDURE:
1.
2.
3.
4.
5.
6.
The connections are made as shown in the circuit diagram.
First DIAC is connected in forward direction .
The input supply is increased in step by step by varying the RPS .
The corresponding ammeter and voltmeter readings are noted and tabulated.
Then the DIAC is connected in reverse condition.
The above process is repeated .
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IE(3341105)SEM-4
Characteristics Curve:
OBSERVATION TABLE:


MT2- Positive & MT1-Negative.
IG =
Sr. No.


Vm1m2
I Diac
MT2- Negative & MT1-Positive.
IG =
Sr. No.
Vm1m2
I Diac
CONCLUSION:
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EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:4
AIM: To perform phase control of TRIAC with DIAC.
APPARTUS:
230V to 50V Transformer, Rheostat (570ohm, 1.2A), Phase control Kit of Triac, CRO, true rms
meter,
THEORY:
SCR may be triggered ON at any instant of time in one cycle of input voltage. This can be
accomplished by providing proper triggering at the gate terminal. In this experiment, we provide
the gate signal through DIAC and without DIAC. While triggering the SCR with DIAC, the
average load voltage will be nearer to zero. This is due to symmetrical operation of DIAC in both
the half cycles of AC power supply. So load gets equal AC power in each half cycle of the AC
power supply.
CIRCUIT DIAGRAM:
PROCEDURE:
1.
2.
3.
4.
5.
6.
Connect the circuit as shown in the Fig.
Switch on the AC mains.
Very pot R1 and observe the waveforms across the TRIAC and load resistance.
Measure the all parameters as per the observation table.
Repeat steps 3 to 5 for new value of R1.
Switch off AC mains and disconnect the circuit.
Power PL = (VLrms X VLrms)/RL
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IE(3341105)SEM-4
OBSERVATION TABLE:
RL=570 Ohms
SR.
No
R(Kohm)
(RB +1K)
VLrms
(Volts)
PL
(WATTS)
Conduction angle(degree)
Positive Cycle Negative cycle
CONCLUSION:
16
VL
avg
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EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:5
AIM: - To perform an UJT synchronized triggering scheme of SCR..
APPARATUS:
UJT synchronized triggering Kit, Transformer 230V/50V, CRO,
THEORY:
Triggering of SCR using UJT
The ac supply voltage is rectified by the bridge rectifier formed by the didoes D1 ,D2,D3,and
D4.This full wave rectified voltage is then applied to a zener diode via a current limmiting series
resistor. The zener diode will clamp this rectified voltage to Vz as shown in the waveforms of
fig.The zener voltage Vz is then used as supply voltage Vbb for the relaxation oscillator. The
capacitor charged through the potentiometer R1.When the capacitor voltage equals the peak
voltage Vp of the UJT ,it turns on. Then capacitor discharges through emmiter(E),base(B) and
primary winding of pulse transformer. Due to primary current , a pulse is generated on the
secondary side of the pulse transformer. These pulse are used as triggering pulses for the SCR.As
the capacitor discharges and Vc reaches the peak voltage Vv, the UJT is turn off and the
capacitor start charging again through R1 . the charging rate of capacitor is decided by the value
of resistor R.Therefor it is possible to change the firing angle α by varying the potentiometer
R1.The firing angle can be changed from 0 to 180 degree.
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EC DEPARTMENT
IE(3341105)SEM-4
PROCEDURE:
1.
2.
3.
4.
5.
6.
Connect the circuit as shown Figure.
Switch on AC mains.
Adjust the value of potentiometer step-by-step .
See the waveform across the load and measure the Conduction Angle.
Repeat the step 3 to 4 for different value of Potentiometer resistor R1.
Switch off the supply and disconnect the circuit.
OBSERVATION TABLE:
Sr.No.
Req = 100 Ω + R1
Conduction Angle of SCR (α)
WAVEFORM:
CONCLUSION:
18
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EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:6
AIM: To study the performance & waveforms of HWR by using RC triggering Circuit.
APPARATUS:
Transformer, SCR , Resistor, Capacitor, Ammeter, Voltmeter.
THOERY:
In the negative half cycle of the AC Supply, diode D2 is forward biased. It will short circuit the
potentiometer R and the capacitor C is charged to negative peak voltage through D2 as shown in
fig with its upper plate negative with respect to its lower plate. In the positive half cycle, D2 is
reverse biased. The capacitor C will charge through R to the trigger point of the SCR in the time
determined by the RC time constant and the rising Anode voltage. The diode D1 will isolate and
protect the gate cathode junction against reverse voltage. As soon as the capacitor voltage will
become sufficiently positive to forward bias D1 and the gate cathode junction of SCR, the SCR
will be turned on. As soon as SCR is turned on, the voltage across it reduces to a very low value
and the gate current goes to zero. The firing angle α can be changed from 0 to 180 degree by
varying the potentiometer R. Note that a positive as well as negative voltage appear across the
capacitor. By adjusting the value of R it is possible to vary a delay in turning on the SCR from 0
to 10 msec and vary the firing angle from 0 to 180 degree. It is evident that this is a half wave
circuit because α can be controlled in only one half cycle of the supply voltage.
CIRCUIT DIAGRAM:
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EC DEPARTMENT
IE(3341105)SEM-4
PROCEDURE:
1. Connections are made as shown in the circuit diagram.
2. Switch ON power Supply.
3. Vary the 500KΩ resistor and Observe the waveform across the thyristor and find
Firing angle of the thyristor.
4. Draw the Waveform . and repeat the step 4 for various firing angle by varying the
potentiometer resistor .
5. Switch OFF the supply and disconnect the circuit.
.
WAVEFORM:
CONCLUSION:
20
GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:7
AIM: To study the performance & waveforms of FWR by using RC triggering Circuit.
APPARATUS:
Transformer, SCR , Resistor, Capacitor, Ammeter, Voltmeter.
THOERY:
In the RC half wave triggering circuit power can be delivered to the load only during the positive
half cycle of supply because the SCR conducts only when it is forward biased.This limition can
be overcome in several ways;here the ac line voltage is converted to Pulsating dc bt the full wave
diode bridge.This allows the SCR to be triggred ON for both half cycle of the line voltage,which
doubles the available power to the load. The diode D1 through D4 form a brigde rectifier.so we
get rectified voltage across the rectifier circuit.Then this rectified voltage is applied power
ciruit.The Capacitor is Charges through R.so by Varying the value of R we can vary the firing
angle α.The firing angle can be controlled in both the half cycle of ac supply.Hence this is full
wave circuit.
CIRCUIT DIAGRAM:
PROCEDURE:
1. Connections are made as shown in the circuit diagram.
2. Switch ON power Supply.
3. Vary the 500KΩ resistor and Observe the waveform across the thyristor and find
Firing angle of the thyristor.
4. Draw the Waveform . and repeat the step 4 for various firing angle by varying the
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EC DEPARTMENT
potentiometer resistor .
5. Switch OFF the supply and disconnect the circuit.
WAVEFORM:
CONCLUSION:
22
IE(3341105)SEM-4
GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:8
AIM:To Implement Squential Timer Using IC-555.
APPATATUS:
Oscilloscope,Function Generator ,IC-555,Resistor,Capacitor.
THEORY:
The circuit works under a simple monostable mode connected in sequence together.As we all
know that in monostable mode of operation the IC555 employs a trigger in order to switch its
output states. As We know that the three 555 IC's was wired as monostable multivibrator that is
each needs a negative going trigger to activate the devices connected through the relay.Initailly
the negative trigger from the clock source activates the first timer IC making it to give high
output activating the relay.The output pin of the IC1 was connected to the trigger input of the
IC2.When the high output was given by the IC1 the output of the IC2 remains in low state but as
soon as the output of the IC1 becomes low, it turns the output of the IC2 into high state thereby
making it to activate the second relay in sequence.In the same manner the IC3 will be activated
after obtaining low output from the output pin of the IC2. The specifications of the R and C
values play a significant role in the circuit since it decides the time period of the output.The
input clock pulse also plays a vital role in switching the circuits sequentially. The output time for
the IC 555 was given by the formula
T = 1.1*R*C .
CIRCUIT DIAGRAM:
23
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EC DEPARTMENT
IE(3341105)SEM-4
PROCEDURE:
1.
2.
3.
4.
5.
Connections are given as per the circuit diagram.
+ 5V supply is given to the + Vcc terminal of the timer IC.
A negative trigger pulse of 5V, 2 KHz is applied to pin 2 of the 555 IC.
At pin 3 the output waveform is observed with the help of a CRO
At pin 6 the capacitor voltage is obtained in the CRO and draw the voltage waveforms .
CONCLUSION:
24
GP,GANDHINAGAR
EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL:9
AIM:To Implement Timer Delay Using IC-555.
APPARATUS:
Oscilloscope,Function Generator ,IC-555,Resistor,Capacitor.
THEORY:
When a negative ( 0V ) pulse is applied to the trigger input (pin 2) of the Monostable configured
555 Timer oscillator, the internal comparator, (comparator No1) detects this input and “sets” the
state of the flip-flop, changing the output from a “LOW” state to a “HIGH” state. This action in
turn turns “OFF” the discharge transistor connected to pin 7, thereby removing the short circuit
across the external timing capacitor, C1. This action allows the timing capacitor to start to charge
up through resistor, R1 until the voltage across the capacitor reaches the threshold (pin 6) voltage
of 2/3Vcc set up by the internal voltage divider network. At this point the comparators output
goes “HIGH” and “resets” the flip-flop back to its original state which in turn turns “ON” the
transistor and discharges the capacitor to ground through pin 7. This causes the output to change
its state back to the original stable “LOW” value awaiting another trigger pulse to start the timing
process over again. Then as before, the Monostable Multivibrator has only “ONE” stable state.
The Monostable 555 Timer circuit triggers on a negative-going pulse applied to pin 2 and this
trigger pulse must be much shorter than the output pulse width allowing time for the timing
capacitor to charge and then discharge fully. Once triggered, the 555 Monostable will remain in
this “HIGH” unstable output state until the time period set up by the R1 x C1 network has
elapsed. The amount of time that the output voltage remains “HIGH” or at a logic “1″ level, is
given by the following time constant equation.
τ = 1.1 R1C1
Where, t is in seconds, R is in Ω’s and C in Farads.
CIRCUIT DIAGRAM:
25
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EC DEPARTMENT
IE(3341105)SEM-4
PROCEDURE:
1.
2.
3.
4.
5.
6.
7.
Connections are made as per the circuit diagram.
Pins 4 and 8 are shorted and connected to power supply Vcc (+5V)
Between pins 8 and 7 resistor R1 of 10KΩ is connected . Pins 2 and 6 short circuited.
In between pins 1 and 5 a Capacitor of 0.01µF is connected.
The output is connected across the pin 3 and GND.
In between pins 6 and GND a Capacitor of 0.1µF is connected.
Practically Td and Tc are measured and wave forms are noted and theoretical Values are
verified with practical values .
CONCLUSION:
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EC DEPARTMENT
IE(3341105)SEM-4
PRACTICAL :10
AIM: To study the operation of a Synchro Transmitter (CX) and Synchro receiver (CR)
.
Connected together.
THEORY:
When mechanical input is applied to the rotor of the Synchro transmitter CX, it is converted into
an electrical signal and then transmitted to the rotor of a synchro receiver which changes its
position according to the input signal.
CIRCUIT DIAGRAM:
PROCEDURE:
1.
2.
3.
4.
5.
Connect the circuit Diagram as shown in fig.
Initially keep the rotors of CX and CR at a position marked 0°.
Turn the rotor of CX in a clockwise direction to 45° .The rotor of CR also turns to 45°.
Turn the transmitter rotor through an angle of 90°,180°,……and so on.
Observe the rotor of CR which is exactly follows the input signal applied to the rotor of
CX.
CONCLUSION:
27