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GEC DAHOD

B.E. EC



Laboratory Manual


For


POWER ELECTRONICS


B.E (E.C)


SEM VII




Electronics & Communication Department

Government Engineering College Dahod

www.gecdahod.ac.in












GEC DAHOD

B.E. EC



Index


Name:

_____________________________________

Roll No._____________


Sr.

No

Experiment Title

Page

Date


Initials

of Staff

Remar
k

Fro
m

To

1

To Study & Perform about the
C
haracteristics of DIAC
.






2

T
O

Study the Characteristics of a SCR and
measure Holding Current (I
H
) And


Latching Current (I
L
) of SCR.






3

To Study
t
he Characteristic
o
f UJT.






4

To Study the Characteristics of TRIAC







5

To
O
btain
t
he
m
ost
p
referable
m
ode
o
f
o
peration
o
f

TRIAC
.






6

To Perform UJT as a Relaxation O
scillator
.






7

To

Study the Triggering C
ircuit using PUT.






8

To Study and Perform T
riggering scheme of
SCR






9

To
Study & Perform the Phase C
ontrol of
TRIAC with & without DIAC.







10

To Study the Characteristics of MOSFET
(Metal Oxide Semiconductor Field
Effect

Transistor)








11

To Perform The Lamp Dimmer Circuit
Using TRIAC.







12

To Study the Thyristor Commutation Circuit








13

To S
tudy 3
-
Phase half
-
wave Uncontrolled &
Controlled Rectifier






14

To S
tudy 3
-
Phase full
-
wave Uncont
rolled &
Controlled Rectifier






15

To Study the Inverter Circuit








GEC DAHOD

B.E. EC



Experiment
-
1
: DIAC characteristics



Date
: _
_______


1.
Aim
:

To study & perform about the characteristic
s of DIAC
.

2.
Requirements:
C.R.O
,

DIAC
,

Power supply 23
0
V
-
50Hz
,

Multimeter
,

Connecting wires
.

3.
Pre
-
E
xperiment Exercises





Brief Theory















































GEC DAHOD

B.E. EC










MT
1



MT
1












MT
2





MT
2











Fig:1 DIAC Structure Fig:2 DIAC Symbol








+I




Blocking State for


MT
1

(
+) w.r.t. MT
2



Ve Half Cycle




Conduction State for




+Ve Half Cycle




+I
BO



-
V
BO





-
V

+V



+V
BO





-
I
BO



Conduction State for



-
Ve Half Cycle






MT
1

(
-
) w.r.t. MT
2



-
I


Fig
:

3

Characteristics of DIAC



4.
Laboratory Exercises


P


N


P



N

N


GEC DAHOD

B.E. EC




A)

Procedure:

1.

Connect the ckt as shown in fig
.
4
.

2.

Draw the voltage w/f and V
-
I characteristics of DIAC, when it
conduct.




















B)

Observation

Table


1. Forward Bias

Sr.

No.

Supply
Voltage Vs

Voltage Across
DIAC

Vd

Current
Through DIAC
Id






























2. Reverse Bias

Sr.

No.

Supply
Voltage
Vs

Voltage Across
DIAC

Vd

Current
Through DIAC
Id






























5. Post
E
xperiment
E
xercises


A)

Conclusion



V



I



MT
1


MT
2


Fig:
4

Circuit Diagram




+
-

0
-
50V



4.7KΩ
=
=
+
=
=
=
-
†††
=
=

GEC DAHOD

B.E. EC




B) Questions


1. Why

DIAC is named so?








2. Wh
ich

are

the application
s

of DIAC

?










3.

What is Break over voltage for DIAC

?































GEC DAHOD

B.E. EC



E
xperimen
t
-
2
: SCR Characteristics






Date:

________


1.
Aim:

T
O

Study
t
he Characteristics of
a

SCR and
measure Holding

Current (I
H
) And


Latching Current (I
L
) of SCR.

2.
Requ
irements:

SCR
,

C
ircuit board
,

Power supply
,

Multimeter
,

Connecting wires

3.
Pre
-
E
xperiment Exercises

Brief Theory
















































GEC DAHOD

B.E. EC


























































+

-

I

1KΩ

R
1

0
-
50V
DC

0
-
5V
DC

+

-

4.7K


R
2

I

+

-

-

+

+

-

A

G

K

V

Fig:3 Circuit Diagram for SCR Characteristic


N

P

N

P

Anode (A)

Cathode (K)

Gate (G)

j
1

j
2

j
3

Fig:1 Construction of SCR

A

G

K

Fig:2 Symbol of SCR


GEC DAHOD

B.E. EC









+I
A






Forward voltage Drop




Latching Current




i
g3

> i
g2
> i
g1






Holding




Reverse Br
eak

Current


i
g3


i
g2


i
g1



Down Voltage

I
H





i
g
=0



-
V








Forward


Forward




Leakage


Break Over



Reverse


Current


Voltage


Leakage


Current







-
I

Fig:4
V
-
I c
haracteristics of SC
R


4.

Laboratory Exercises

A)
Procedure

Part:1
Step
s

for SCR Characteristics

1.

Connect the circuit as shown in
fig.3.

2.

Set the anode voltage (V
AK
) to some fix value (25v).

3.

Now slowly increase the gate voltage and measure the reading of current I
A
, I
G

and vo
ltage V
AK
.

4.

Repeat the step (3) until the SCR is Turn
-
ON
.

5.

When SCR is ON
,

st
o
p increa
sing the Gate voltage and measure the value I
A
,
I
GO

and V
AK
, where I
GO

is the
c
urrent requires

to Turn
-
ON the SCR.

6.

Now reverse the polarity of supply voltage V
AK

and take t
he reading for SCR
reverse bias
.

7.

Plot the V
-
I Characteristics of SCR from the observation table.














GEC DAHOD

B.E. EC



B)

Observation
s



1. Forward

Bias

Sr.

No.

Supply
Voltage Vs

Voltage Across
SCR

Current
Through SCR


































2. Reverse

Bias

Sr.

No.

Supply
Voltage
Vs

Voltage Across
SCR

Current
Through SCR






























Part
: 2

Steps for Measuring I
H

and I
L

1.
Connect the circuit as shown in fig
3.

2.
S
et the g
ate
current slightly higher then the I
GO.

3.
Now slowly

increase the anode voltage

(V
AK
)

until

the ammeter connected to
anode
shows some
current
reading (
I
A
)
.

4 .
Now turn
-
off the gate voltage and see if the

Anode

current meters reduce to
zero value th
e
n a
gain give the gate voltage and increase the anode
voltage
(
V
AK
)
.

5.
Repeat step 4 until you get the some reading on
Anode
current meter, even after



removing the gate voltage. This current is known as Latching current
(I
L
)
.

6.

Now slowly reduce
the anode voltage to zero

so

the

Anode

current meter
reading
s

also reduce

to zero.


7.
At one value of anode voltage the

Anode

current (
I
L
)

suddenly reduce to zero
this
c
urrent

known as the Holding current
(I
H
)
.

8.
Note down the value of
I
H

and
I
L
.




5. P
ost
E
xperiment
E
xercises


A)
Conclusion













GEC DAHOD

B.E. EC








Operation of SCR


1.

Operation without gate
















2.

Operation with gate
































GEC DAHOD

B.E. EC



Experimen
t
-
3
:
UJT

Characteristics






Date:

________



1.

A
im
:

To Study The Characteristic
o
f UJT.


2.

Requirements:

UJT circuit board,

Power supply, Multimeter, Connecting wires



3.

Pre
-
E
xperiment Exercises






Brief Theory




















































GEC DAHOD

B.E. EC






































Cut off

Negative




Saturation

Region

Resistance Region



Region



Vp

Peak Point


















Valley Point




V
E (
sat)


Vv





I
P


I
v

50

I
E

(mA)








I
EO

(µA)

Fi
g:
3
Characteristics of UJT


B
2

B
1

E

N
-
Type Bar

P
-
Type Bar

Fig: 1

Construction of UJT


B
2


B
1


E


Fig: 2 Symbol of UJT



GEC DAHOD

B.E. EC































4.
Laboratory Exercises


A)

Procedure


1. Connect the DC variable power supply and fixed power supply to


their respective terminal with proper polarity.


2. Connect
the meters for measuring current and voltage.

3. Increase the supply voltage until the UJT fires; record the maximum


value of I
E

prior to firing of UJT as I
P
.

4. Tabulate the reading in the observation table.

5. Plot the graph of characteristics of

UJT.

6. Make the conclusion.


B)

Observations



Sr.
No.

Vs(volt)

V
E
(volt)

I
E
(mA)
































5. Post
E
xperiment
E
xercises


A)

Conclusion






47E

+

-

-

4K7

R
1

+

-

I

V

R
2

R
3

E

B
2

B
1

330Ω
=
ㄲ1
DC


0
-
10
V
DC


Fig: 4

Circuit Diagram of UJT Characteristic


+

-

+


GEC DAHOD

B.E. EC



Experimen
t
-
4
:

TRIAC

characteristics





Date:

________


1.

Aim
:

To Study
the

Characteristics
of TRIAC


2.

Requirements
:
TRIAC

circuit board,

Power supply
(0
-
60v
)
,

Multimeter,

Connecting


wires


3
.

Pre
-
E
xperiment Exercises







Brief
Theory


















































GEC DAHOD

B.E. EC










































4.
Laboratory Exercises



A)

Procedure







1. Connect the circuit as shown in fig.

2
.



2. Apply the
min
imum
Gate current
requires to turn on the

TRIAC
.



3. Slowly increase the
supply

voltage until the
TRIAC

comes in ON state.


4. Measure the reading of voltage and current for different value.



5 Reverse the polarity of supply and

repeat the step 2 to 5.



6. Plot the V
-
I characteristic of
TRIAC

from the reading.








Anode Current(A)

+I

Forward voltage Drop

Latching

Current

i
g3

> i
g2
> i
g1


i
g3



i
g2


i
g1


Holding


Current I
H

(mA)

Negative Break

Down Voltage

-
V

Reverse Leakage Current

Forward

Leakage

Current

Positive

Break Over

Voltage


Reverse

Voltage

Drop


Anode Current(A)

-
I

+V


i
g1


i
g2

i
g3

i
g1

< i
g2

<


i
g3


Fig:

1 V
-
I

Characteristics of
TRIAC



GEC DAHOD

B.E. EC



I

I

V







+
-






-


-


+








330
Ω









1












+










+




+


















0
-
5V






G




-












-




































B)

Obs
ervations

1. Forward Bias

Sr.

No.

Supply
Voltage Vs

Voltage Across
TRIAC

Current Through
TRIAC






























2. Reverse Bias

Sr.

No.

Supply
Voltage
Vs

Voltage Across
TRIAC

Current Through
TRIAC































5
. Post
E
xperiment
E
xercises


A)
Conclusion







Fig.
2
TRIAC Circuit


MT
2

MT
1

G

0
-
30V
DC

-


GEC DAHOD

B.E. EC




Experimen
t
-
5
:

The most preferable mode for

TRIAC






Date:

________


1.

Aim
:
-

To
o
btain
t
he
m
ost
p
referable
m
ode
o
f
o
peration
o
f

T
RIAC
.

2.

Requirements:

TRIAC

circuit board,

Power supply
(0
-
60v
)
,

Multimeter,

Connecting


wires


3
.

Pre
-
experiment Exercises





Brief Theory


















































GEC DAHOD

B.E. EC



4.
Laboratory Exerci
ses



A)

Procedure


1.

Connect the MT2 terminal in +ve and MT1 to

ve and gate terminal to +ve. This
is the

I
+

mode.


2.
Now apply the supply voltage to
TRIAC

and increase the gate voltage until the


TRIAC

fired.



3.
Measure this gate current as Ig and gate voltage as Vg and note down this value


in the

observation table.


4.
Repeat the process for all the modes and measure the different value of Ig and


Vg.



5.
From the observation table find out the most preferable mode of
TRIAC

firing

.

Mode

MT
2

MT
1

G

I
+

+

-

+



















Mode

MT
2

MT
1

G

I
-

+

-

-





































Mode

MT
2

MT
1

G

III
+

-

+

+

I


I

V

0
-
5V

0
-
30
V

G

MT
2

MT
1

1


330
Ω

-

-

+

+

+

+

-

-

-

+

I


I

V

0
-
5V

0
-
30
V

G

MT
2

MT
1

1


330
Ω

+

-

-


+

+

+

-

-

-

+

I


I

V

0
-
5V

0
-
30
V

G

MT
2

MT
1

1


330
Ω

-

+

+

+

+

+

-

-

-

-


GEC DAHOD

B.E. EC








Mode

MT
2

MT
1

G

III
-

-

+

-




















Fig:

1.
Mode

of
operation

o
f
TRIAC



B)

Observations





5. Post
E
xperiment
E
xercises


A)

Conclusion

















Mode

MT
2

MT
1

G

Gate Current
Ig

I
+

+

-

+


I
-

+

-

-


III
+

-

+

+


III
-

-

+

-


I


I

V

0
-
5V

0
-
30
V

G

MT
2

MT
1

1


330
Ω

+

+

-

+

+

+

-

-

-

-


GEC DAHOD

B.E. EC



Experiment
-
6: UJT as a Relaxation Oscillator


Date: ________



1. Aim:


To perform UJT as a
relaxation oscillator
.


2. Requirements:

UJT relaxation oscillator board, Power supply, CRO, Connecting wires

3. Pre
-
Experiment Exercise


Brief Theory





































GEC DAHOD

B.E. EC

































Fig.1 Circuit Diagram


4. Laboratory Exercise


A)

Procedure


1. Connect the circuit as shown in fig.1.


2. Apply the supply voltage to UJT.


3. Observe the waveform across t
he UJT when it is in the off
condition.


B) Observ
ation Table



Sr.
No.

Practical
Charging

Time,

T
1

Practical
Discharging
Time,

T
2

Value of R

Theoretical
Charging Time,

T
1
= 0.69*RC

Theoretical
Discharging Time,

T
2

=0.69* RB
1
C





















































































+12V

R=0
-
100KΩ
=
C=〮ㆵc
=
b
=
B
2

B
1

R=1KΩ
=
=
o
B2
=330Ω
=
o
B1
=47Ω
=

GEC DAHOD

B.E. EC





5. Post Experimental Exercis
e


A) Conclusion

































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Experiment
-
7: T
riggering circuit using PUT



Date: _________



1. Aim:

To study the triggering circuit using PUT.


2.

Requirements
:

PUT

circuit board, Power supply, C.R.O, Connecting wires


3.Pre
-
Experiment Exercise


Brief Theory















































GEC DAHOD

B.E. EC



























Fig.
1 Circuit Diagram





4. Laboratory Exercise

A)

Procedure

1. Construct the cir
cuit shown in the figure.

2. Observe the waveform at G,A & K and draw them.


B)

Observation Table



Sr.

No.

R
a

T
c

T
d






























5. Post Experimental Exercise


A) Conclusion








K

R
1
=4.7K

+12V

R
a
=470K

A

G

PUT

R
2
=6.7K

R
k
=100Ω

C=2.2nF

PUT


A G K


GEC DAHOD

B.E. EC



Experiment
-
8: T
riggering

scheme of SCR





Date: ________


1. Aim:

To study and perform triggering scheme of SCR

2. Requirements
:

SCR Trainer kit, Rheostat, CRO, Transformer, DMM

3. Pre
-
Experiment Exercise


Brief Theory


































GEC DAHOD

B.E. EC


























Fig.
1

RC triggering Scheme of SCR




4. Laboratory Exercise

A)

Procedure

1. Connect the circuit as shown in fig.1.

2. Apply the supply voltage to SCR.

3. Observe the waveform across the SCR wh
en it is in the off Condition

4. Now adjust the value of resistor R
2

to turn on the SCR and observe the waveform
across it.

5. Find the firing angle and conduction angle of the SCR from the Waveform.

6. Vary the value of R
2

and see the effect on
the output waveform and take the
different readings of conduction angle and compare it with the calculated value.



B) Observation Table



Sr
No.

T
ON

sec

Resistor

R
2

Firing

Angle α

Conduction

Angle,

φ = 180
-

α





































5. Post Experimental Exercise


A) Conclusion





15 Vp
-
p AC

O/P

Rs = 70Ω

R
1

=
1KΩ

G


R
2

=


470KΩ


C =
0.01µF

K

A

D
1

D
2


GEC DAHOD

B.E. EC



Experiment
-
9: Phase Control of TRIAC With
& Without DIAC











Date:________


1. Aim:

To study & perform the phase control of TRIAC with & without DIAC.

2. Requirements
:

Ci
rcuit board,

Rheostat,

Voltmeter, CRO, Transformer,


3. Pre
-
Experiment Exercise


Brief Theory















































GEC DAHOD

B.E. EC







Circuit diagram


















Fig.1

Phase Cont
rol of TRIAC



4. Laboratory Exercise


A)

Procedure

1. Connect the circuit as shown fig.1.

2. See the waveform across TRIAC without connecting the DIAC.

3. Measure the TON time and conduction angle for both the half cycle.

4. Calculate conduction angle =
ON

time *360/20.

5. Take different reading for different values of R and note down it.

6. Now connect the DIAC in the firing circuit of TRIAC and observe the wave form
across the TRIAC.

7. Repeat the step 3 to 5.

8. Compare the both the reading of conduction

angle for positive half cycle and
negative half cycle.



B)

Observation Table



With DIAC














Sr
No.

T
ON

(ms)

Α
=
䍡汣u污瑥d⁁湧=e
=
φ = T
ON

360 /
20msec

+ve

-
ve

+ve

-
ve

+ve

-
ve


















































15 Vp
-
p AC

O/P

Rs = 70Ω
=
刱‽R
1KΩ
=

1

MT
2

+

-


GEC DAHOD

B.E. EC



Wi
thout DIAC















5. Post Experimental Exercise


A) Conclusion































Sr
No.

T
ON

(ms)

Α

Calculated Angle

φ = T
ON

360 /
20msec

+ve

-
ve

+ve

-
ve

+ve

-
ve



















































GEC DAHOD

B.E. EC



Experiment
-
10: C
haracteristics of MOSFET




Date: ________


1.
Aim:

To Study the Characteristics of MOSFET (Metal Oxide Semiconductor Field Effect



Transistor)

2.
Requirements
:

Experimental board
, Multimeter, Connecting wires.

3. Pre
-
Experiment Exercise


Brief Theory















































GEC DAHOD

B.E. EC
















































4. Laboratory Exercise

A)

Procedure

1. Connect the DC va
riable power supply and fixed power supply to their respective
terminal with proper polarity.

2. Connect the meters for measuring current and voltage.

3. Increase the supply voltage V
IN

in step of 1V with the help of pot when keeping V
GS

at
a constant v
alue.

4. Tabulate the reading in the observation table.

5. Now increase the value of VGS and repeat step 3and 4.

Drain

Substrate

Oxide Layer

(SiO
2
)

Gate

N

P

N

Source

Fig
.1

Construction of N
-
Channel MOSFET

Drain

Gate

Source

Substrate

Fig.
2

Symbol of

N
-
Channel MOSFET

Fig
.
3 Circuit Diagram of MOSFET

I
D

R
2

R
1

V
DS

V
GS

V
GG

+

+

-

-

V
DD

S

G

D

0

=

DC


GEC DAHOD

B.E. EC



6. Plot the graph of characteristics of UJT.






























5. Post Experimental Exercise


A)

Conclusion

















Fig
.
4 Characteristics of MOSFET

0

V
GS

=
-
4

V
GS

=
-
3

V
GS

=
-
2

V
GS

=
-
1

V
GS

= 0

V
GS

= 1

V
D
S

I
D


GEC DAHOD

B.E. EC



Experiment
-
11: The Lamp Dimmer Circuit Using TRIAC



Date: _______


1. Aim:


To Perform The Lamp Dimmer Circuit Using TRIAC.

2. Requirements
:
Experiment
al Board, Multimeter, CRO, Resistance decade box, connecting


wires.

3. Pre
-
Experiment Exercise


Brief Theory


































GEC DAHOD

B.E. EC




Circuit Diagram



























Fig.1


4. Laboratory Exercise

B)

Procedure

1. Construct the circuit shown in the figure.

2. Connect the oscilloscope across load. Don’t connect probes directly


to the load but use divider network and connect the probes there.

3. Vary the firing angl
e by varying the resistance using decade box and


observe the waveforms.

4. Draw waveforms at 45
0
and 90
0

firing angles.


B)

Observation Table


Sr
No.

Current I
S
(Amp)

Load Voltage (V
L
)

Thyristor
Voltage V
T
(Volt)

Variable
Resistor
-
R(KΩ)







































5. Post Experimental Exercise



A) Conclusion





230
AC

R1 =
1KΩ

G


R
1
=



1
0KΩ


C=1µF

MT
1

MT
2

L

C

R

Bulb


GEC DAHOD

B.E. EC



Experiment
-
12: Thyristor Commutation Circuit


Date:

________



1. Aim:


To Study the Thyristor Commutation Circuit


2. Requirements
:
Exp
erimental board, Multimeter, connecting wires


3. Pre
-
Experiment Exercise


Brief Theory












































4. Post Experimental Exercise


A) Conclusion




GEC DAHOD

B.E. EC



Experiment
-
13: 3
-
Phase Half
-
wave Uncontrolled & Controlled Rectifier




Date: ________


1. Aim:


To study 3
-
Phase half
-
wave Uncontrolled & Controlled Rectifier

2. Requirements
: Trainer for 3
-
phase controlled
-
uncontrolled rectifier, CRO.

3. Pre
-
Experiment Exercise


Brief Theory














































GEC DAHOD

B.E. EC



4. Laboratory Exercise

B)

Procedure

1. Connect the components such that 3
-
phase half wave uncontrolled rectifier will be
developed.

2. Connect load across the DC+ and N terminal.

3. Connect oscilloscope across it using voltage divider and observe wave
form.

4. Replace diode with the SCR and develop 3
-
phase controlled rectifier.

5. Repeat step 2 & 3.

Vary the phase control knob and see the waveform.


5. Post Experimental Exercise


A) Conclusion











































GEC DAHOD

B.E. EC



Experiment
-
14: 3
-
P
hase Full
-
wave Uncontrolled & Controlled Rectifier




Date: ________


1. Aim:


To study 3
-
Phase full
-
wave Uncontrolled & Controlled Rectifier

2. Requirements
: Trainer for 3
-
phase controlled
-
uncontrolled rectifier, CRO.

3. Pre
-
Experiment Exercise


B
rief Theory














































GEC DAHOD

B.E. EC



4. Laboratory Exercise

A)

Procedure

1. Connect the components such that 3
-
phase full wave uncontrolled rectifier will be
developed.

2. Connect load across the DC+ and DC
-

terminal.

3. Connect oscillosco
pe across it using voltage divider and observe waveform.

4. Replace 3 diodes with the SCR and develop 3
-
phase full wave half controlled
rectifier.

5. Repeat step 2 & 3.

6. Vary the phase control knob and see the waveform.


5. Post Experimental Exercise


A
) Conclusion


































GEC DAHOD

B.E. EC



Experiment
-
15: The Inverter Circuit


Date
:

________

1. Aim:


To St
u
dy the Inverter Circuit

2. Pre
-
Experiment Exercise


Brief Theory






















Series Inverter:


























GEC DAHOD

B.E. EC






Operation:















Disadvantages:




































GEC DAHOD

B.E. EC













3. Post Experimental Exercise



A) Conclusion