ALAGAPPA CHETTIAR GOVERNMENT COLLEGE OF
ENGINEERING AND TECHNOLOGY KARAIKUDI-630 003
(An Autonomous Institution Affiliated to Anna University)
19EEL61 POWER ELECTRONICS LABORATORY
RECORD
Submitted by:
Name: .......................................................................
Reg. No: .....................................................................
Sem
1
: VI Branch:
EEE
ALAGAPPA CHETTIAR GOVERNMENT COLLEGE
OF ENGINEERING AND TECHNOLOGY, KARAIKUDI630 003
(An Autonomous Institution Affiliated to Anna University)
This is to certify that it is the bonafide record of work done by
...................................................................... (Reg. No...........................)
of VI Semester Electrical and Electronics Engineering Branch in the
19EEL61 POWER ELECTRONICS LABORATORY during the
year 2022 - 2023.
STAFF INCHARGE
Submitted for the practical examination held on.............................
Internal Examiner
External Examiner
2
INDEX
S.NO DATE
EXPERIMENTS
1.
V-I CHARACTERISTICS OF SCR
2.
V-ICHARACTERISTICS OF MOSFET
3.
SINGLE PHASE AC TO DC FULLY
CONTROLLED CONVERTER
4.
SINGLE PHASE AC TO DC HALF
CONTROLLED CONVERTER
5.
STEP DOWN CHOPPER
6.
STEP UP CHOPPER
7.
SINGLE PHASE INVERTER
8.
THREE PHASE INVERTER
9.
THREE PHASE FULL CONVERTER
10.
V-I CHARACTERISTICS OF TRIAC
11.
SINGLE PHASE AC VOLTAGE
CONTROLLER WITH R LOAD
12.
STEP UP DOWN CHOPPER
AVERAGE MARKS
MODEL EXAM MARKS
INTERNAL MARKS
3
MARKS
SIGN
CIRCUIT DIAGRAM - SCR
MODEL GRAPH – SCR
4
EX NO:
DATE:
V-I CHARACTERISTICS OF SCR
AIM:
To conduct an experiment and obtain the anode forward conduction
characteristics of the given SCR also find the latching and holding currents of
the given SCR.
APPARATUS REQUIRED:
S.No.
Name of the item
Type
Range
Quantity
TYN612
600V,12A
1
1
SCR module
2
Ammeter
MC
(0-200) mA
1
3
Ammeter
MC
(0-50) mA
1
4
Voltmeter
MC
(0-30) V
1
5
Digital Multimeter
-
-
1
6
RC Firing Module
-
-
1
7
Rheostat
-
8
CRO
-
-
1
9
CRO probe
-
-
1
10
Patch Cards
-
-
10
220/2A
1
THEORY:
The SCR is a four layer three terminal semiconductor device. The
terminals are anode, cathode and gate. Anode is always at a higher positive potential
than the cathode. When the applied potential is increased the forward bias at the outer
layer and the reverse at the inner layer increasing avalanche multiplication
5
TABULATION
IG = Constant=
S.No
mA
Forward Bias
VAK (Volts)
Reverse Bias
IA (mA)
6
VAK (Volts)
IA (mA)
The potential at which the break down occurs is known as breaking or
firing potential.
A voltage applied at the gate terminal can control the break down
voltage. The gate terminal is forward biased with respect to cathode.
The gate terminal is used to control turn on to SCR. Once the SCR is
turn on, the gate looses control.
PROCEDURE:
➢ Connections are made as per the circuit diagram.
➢ Switch on the 230V AC supply through three-pin power
chord.
➢ Keep the gate current (IG) to a suitable value (say minimum of
4 mA to 5mA)
➢ Now slowly increase the anode-cathode voltage (VAK) by
varying the pot till thyristor get turned on, with the indication
that anode cathode voltage decreases to it on state voltage
drop (i.e 0.7V) and the anode current increases.
➢ Note the values of voltmeter (VAK) which is the break over
voltage and the ammeter (I L) which is the latching current
value.
➢ Further, increase the anode current in steps by varying the
anode-cathode voltage and note the readings.
➢ Now reduces the anode cathode voltage (VAK) till the thyristor
turned off and find the holding current.
➢ For various gate current take the readings and tabulate it.
➢ Finally, a graph of anode current Vs anode-cathode voltage is
plotted for various gate current.
7
CALCULATION:
8
RESULT:
9
CIRCUIT DIAGRAM
MODEL GRAPH
10
EX NO:
V-ICHARACTERISTICS OF MOSFET
DATE:
AIM:
To obtain the steady–state output – side characteristics and
transfer characteristics of the given MOSFET, for a specified value of
gate– source voltage.
APPARATUS REQUIRED:
S.No.
Name of the item
Type
Range
Quantity
IRF 740
600V,5A
1
(0-100)
mA
1
1
MOSFET module
2
Ammeter
MC
3
Voltmeter
MC
(0-10)V
1
4
Voltmeter
MC
(0-30) V
1
5
CRO
-
-
1
6
CRO Probe
-
-
1
7
Patch Cards
-
-
10
THEORY:
Bipolar Junction Transistor (BJT) is a current controlled device. In
this device, the flow of collector current is controlled by base current and
hence,current gain is highly dependent on the junction temperature.
However, a power MOSFET is a voltage controlled device, which requires only small
input current. The switching times of these devices are of the order of nanoseconds.
Power MOSFETs are finding increasing applications in low-power, high frequency
converters. MOSFETs do not have the problems of second breakdown phenomena as
11
TABULATION
12
do in BJTs. However, MOSFETs have the problem of electrostatic
discharge and requires special care in handling. In addition, it is
relatively difficult to protect them under short -circuited fault
condition.MOSFETs are generally classified into two types:
Depletion MOSFETs and Enhancement MOSFETs. The three
terminals of MOSFET are named as gate (G), drain (D) and source
(S) .
In case of MOSFET, the gate voltage controls the flow of current
from drain to source. From the output characteristics, drain current (ID)
is a function of drain-to-source voltage VDS with gate -to-source
voltage at constant VGS for an n -channel MOSFET. The output
characteristics for p-channel device are the same except,that the current
and voltage polarities are reversed and hence the characteristics for the
p-channel device would appear in the third quadrant of the ID-VDS
plane.
In power electronics applications, the MOSFET is used as a
switch to control the flow of power to the load. In these applications, the
MOSFET traverses the ID-VDS characteristics from
cutoff region to ohmic region through active region as the device turns
ON, back again when it turns OFF. The cutoff,ohmic and active regions
of the characteristics.
The MOSFET is in cutoff, when VGS < VGS (th), then the device
will act as an open circuit and also the drain -source breakdown voltage
(BVDSS)must be larger than the applied VDS to avoid breakdown due
to avalanche effect.
PROCEDURE:
DRAIN CHARACTERISTICS
➢ Connections are made as per the circuit diagram
➢ Switch on the 230V AC supply through three-pin power chord.
➢ Keep the gate - source voltage (VGS) to a suitable value (say
minimum of 6V to 7V)
➢ Now slowly increase the drain-source voltage (VDS) by
varying the pot till MOSFET get turned on, with the
indication that drain-source voltage decreases
to it on state voltage drop.
13
CALCULATION:
14
➢ Note down the values of drain-source voltage (VDS) and the
drain current (I D)
➢ For various gate-source voltage take the different set of
readings and tabulate it.
➢ Finally, a graph of drain-source voltage (VDS) Vs drain current
(ID) is plotted for various gate-source voltage.
TRANSFER CHARACTERISTICS
➢ Connections are made as per the circuit diagram
➢ Switch on the 230V AC supply through three-pin power chord.
➢ Keep the drain - source voltage (VDS) to a suitable value
➢ Now slowly increase the gate-source voltage (VGS)
➢ Note down the values of gate-source voltage (VGS) and the
drain current (I D)
➢ For various drain-source voltage take the different set of
readings and tabulate it.
Finally, a graph of gate-source voltage (VGS) Vs drain current
(ID) is plotted for various drain-source voltage.
RESULT:
15
CIRCUIT DIAGRAM
16
EX NO:
DATE:
SINGLE PHASE AC TO DC FULLY CONTROLLED
CONVERTER
AIM:
To study the operation of single phase fully controlled bridge
converter with R and RL load both in MATLAB simulation and hardware
implementation.
APPARATUS REQUIRED:
1. Isolation Transformer
2.Half controlled converter power Kit
3.Half controlled converter firing Kit
4.Resistive load
: 100W
5.Inductive load : (0-625) mH
6.CRO
: 20MHz
MODULE DESCRIPTION:
1. Isolation Transformer:
It isolates the main supply and the load. It serves the purpose
of di/dt protection of SCRs and safe measurement of wave
forms by using CRO isolation from electric noise.
2. Power Circuit:
Different power circuit configurations are possible using
SCR and diode modules for half controlled bridge converter,
2 SCRs and 2 diodes of bridge configuration is are used.
3. Firing Circuit:
Each SCR of the above power circuit is to be triggered using
independently isolated phase converter firing unit. Triggered
outputs phase sequence and variation to be checked before
connecting to the power circuit. Phase sequence to be
compared with the power circuit phase sequence.
17
Model graph for R Load
18
4.Load:
Loads can be resistive or inductive or the combination of the both.
THEORY:
A fully controlled converter or full converter uses thyristors
only and there is a wider control over the level of dc output
voltage. With pure resistive load, it is single quadrant converter.
Here, both the output voltage and output current are positive.
With RL -load it becomes a two-quadrant converter. Here, output
voltage is either positive or negative but output current is always
positive. Figure shows the quadrant operation of fully controlled
bridge rectifier with R-load. Fig shows single phase fully
controlled rectifier with resistive load. This type of full wave
rectifier circuit consists of four SCRs.
During the positive half cycle, SCRs T1 and T2 are forward
biased. At ωt = α, SCRs T1 and T3 are triggered, then the current
flows through the L –T1-R load –T3 –N. At ωt = π, supply voltage
falls to zero and the current also goes to zero. Hence SCRs T1 and
T3 turned off.
During negative half cycle (π to 2π).SCRs T3 and T4 forward biased. At ωt = π
+ α, SCRs T2 and T4 are triggered, then current flows through the path N –T2 –
R load -T4 – L. At ωt = 2π, supply voltage and current goes to zero, SCRs T2
and T4 are turned off. For large power dc loads, 3-phase ac to dc converters are
commonly used. The various types of three -phase phasecontrolled converters
are 3 phase half -wave converter, 3-phase semi converter, 3-phase full controlled
and 3-phase dual converter. Three-phase half -wave converter is rarely used in
industry because it introduces dc component in the supply current. Semi
converters and full converters are quite common in industrial applications. A
dual is used only when reversible dc drives with power ratings of and full
converters are quite common in industrial applications.
19
TABULATION:
R - LOAD
Firing
Angle
Firing
Angle in
msec
Magnitude (Average output
Voltage)
Firing
Voltage
Voltage
Voltage
Angle in
measured calculated
Simulated
radians
(V)
(V)
(V)
α=
α=
α=
α=
MODEL CALCULATION :
20
A dual is used only when reversible dc drives with power ratings
of several MW are required. The advantages of three phase
converters over single -phase converters are as under: In 3-phase
converters, the ripple frequency of the converter output voltage is
higher than in single-phase converter.
Consequently, the filtering requirements for smoothing out
the load current are less. The load current is mostly continuous in
3 -phase converters. The load performance, when 3phase
converters are used, is therefore superior as compared to when
single-phase converters are used.
FORMULA REQUIRED:
For R Load,
For RL Load ,
PROCEDURE:
A. Firing Circuit:
1. Power supply is given to firing unit, which will give train of
firing pulses to the thyristors (T1, T2, T3& T4).
B. Fully controlled converter power circuit:
➢ Connections are made as per the circuit diagram for R load
➢ Switch on the triggering kit
➢ Switch on the 230 V AC supply
➢ By varying potentiometer vary the firing angle of the converter in
order to vary the
➢ output voltage step by step.
➢ For each step note down the firing angle, output voltage and load
current.
21
22
RESULT:
23
CIRCUIT DIAGRAM
24
EX NO:
SINGLE PHASE AC TO DC HALF CONTROLLED
DATE:
CONVERTER
AIM:
To study the operation of single phase Half controlled bridge
converter (semiconverter) with R andRL load both in MATLAB
simulation and hardware implementation.
APPARATUS REQUIRED:
1.Isolation Transformer
2.Half controlled converter power Kit
3.Half controlled converter firing Kit
4.Resistive load :100W
5.Inductive load :(0-625)mH
6.CRO : 20MHz
THEORY:
A semi converter uses two diodes and two thyristors and there is a
limited control over the level of dc output voltage. A semi converter is one
quadrant converter. A one-quadrant converter has same polarity of dc
output voltage and current at its output terminals and it is always positive.
It is also known as two -pulse converter. Figure shows half controlled
rectifier with R load. This circuit consists of two SCRs T1 and T2, two
diodes D1 and D2. During the positive half cycle of the ac supply, SCR T1
and diode D2 are forward biased when the SCR T1 is triggered at a firing
angle ωt = α, the SCR T1 and diode D2 comes to the on state. Now the
load current flows through the path L -T1-R load –D2 -N. During this
period, we output voltage and current are positive. At ωt = π, the load
voltage and load current reaches to zero, then SCR T1 and diode D2 comes
to off state since supply voltage has been reversed. During the negative
half cycle of the ac supply, SCR T2 and diode D1 are forward biased.
When SCR T2 is triggered at a firing angle ωt = π + α, the SCR T2 and
diode D1 comes to on state.Now the load current flows through the path N
-T2-R load –D1 -L. During this period, output voltage and output current
will be positive. At ωt = 2π, the load voltage and load current reaches to
zero then SCR T2 and diode D1 comes to off state since the voltage has
been reversed. During the period (π + α to 2π) SCR T2 and diode D1 are
conducting. Vout=(√2Vs)(1+Cosα)/π.
25
MODEL GRAPH FOR R LOAD:
26
PROCEDURE:
1. Connections are made as per the circuit diagram for RL load .
2. Switch on the triggering kit .
3. Switch on the 230V AC supply
4. By varying potentiometer vary the firing angle of the converter in
order to vary the output voltage step by step. For each step note
down the firing angle, output voltage and load current.
5. The output voltage is theoretically calculated for each step and the
readings are tabulated.
FORMULAE REQUIRED:
For R Load,
For RL Load,
MODULE DESCRIPTION
1. Isolation Transformer:
It isolates the main supply and the load. It serves the purpose
of di/dt protection of SCRs and safe measurement of wave
forms by using CRO isolation from electric noise.
2. Power Circuit:
Different power circuit configurations are possible using SCR
and diode modules for half controlled bridge converter, 2
SCRs and 2 diodes of bridge configuration is are used.
3. Firing Circuit:
Each SCR of the above power circuit is to be triggered using
independently isolated phase converter firing unit. Triggered
outputs phase sequence and variation to be checked before
connecting to the power circuit. Phase sequence to be
compared with the power circuit phase sequence.
27
TABULATION:
R - LOAD
Firing
Angle
Firing
Angle in
msec
Magnitude (Average output
Voltage)
Firing
Voltage
Voltage
Voltage
Angle in
measured calculated
Simulated
radians
(V)
(V)
(V)
α=
α=
α=
α=
MODEL CALCULATION:
28
RESULT:
29
STEP DOWN CHOPPER
CIRCUIT DIAGRAM:
MODEL GRAPH:
30
EX NO:
STEP DOWN CHOPPER
DATE:
AIM:
To simulate and experimentally verify the operation of step down chopper and to
obtain the output waveforms for R load and to plot the variation of output voltage
with duty cycle.
APPARATUS REQUIRED:
1.
2.
3.
4.
5.
Desktop/ Laptop computer with MATLAB software
CRO
Chopper kit with control module
Patch cords
Multimeter
FORMULA USED:
STEP DOWN CHOPPER:
Vo=D*Vs
T = Ton + Toff
= Ton / T
Where,
Vo
– output voltage
(V)
– Duty cycle
– Input voltage (V)
– switch ON period
(millisecond)
Toff – switch OFF period
(millisecond)
T
– Total period (millisecond)
Vs
Ton
THEORY:
A chopper is a high speed ON/OFF switch. It connects the source to the
load at a fast speed. In the step-down chopper a variable load voltage can
be obtained from a constant DC supply of magnitude Vs.
31
SIMULATION:
OUTPUT WAVEFORM:
INPUT VOLTAGE:
Vs=12V
OUTPUT VOLTAGE:
D=0.85
Vo =9.8V
Vo =8V for D=0.7
32
The chopper can be turned ON and OFF using control circuit.
During the period Ton the load voltage is equal to the source voltage.
During the interval Toff, load current flows through the freewheeling diode
and therefore the load voltage is zero and the load current is continuous.
Here the average output voltage is less than the supply voltage hence called
as step-down chopper.
PROCEDURE:
1. Step-down chopper circuit is simulated using MATLAB simulation
software.
2. Connections are given as per the circuit diagram.
3. Switch ON the RPS kit and turn ON the triggering circuit.
4. Obtain different set of reading by changing the duty cycle.
5. Observed values are verified with the theoretical values and
simulated values.
6. The output voltage graph is plotted for different duty cycles and
also Vo versus duty cycle 7. (D) graph is also plotted.
33
TABULATION:
STEP DOWN CHOPPER
SI.No Switch ON Period
(TON)
Duty
cycle(D)
Vs =
V
T=
s
Output Voltage(VO)(in volts)
Calculated Simulated Observed
(ms)
34
CALCULATION:
RESULT:
Thus the step down chopper with R load is simulated and experimentally
verified the output waveforms for various duty cycles.
35
STEPUP CHOPPER
CIRCUIT DIAGRAM:
SIMULATION DIAGRAM:
MODELGRAPH:
36
EX NO:
DATE:
STEPUP CHOPPER
AIM :
To simulate the step up chopper with R load and also to obtain the
corresponding voltage waveforms for various duty cycles and verify
experimentally.
APPARATUS REQUIRED:
1. Desktop/Laptop with MATLAB software
2. Step up chopper module
3 .Patch cords
4. CRO
5. Multimeter
FORMULA USED:
STEP UP CHOPPER:
V0 = Vs / (1-D)
D = Ton / T
T = 1/fsw
T = Ton + Toff
Where,
D – Duty cycle,
T – Total time,
fsw– switching
frequency
THEORY:
In the step-up chopper a variable load voltage can be obtained from
a constant DC supply of magnitude Vs. The chopper can be turned ON and
OFF using control circuit. During ON period the inductor stores the energy
37
OUTPUT WAVEFORM:
Vin=12V
D=0.5
V0=20V
Vin=12V
D=0.75
V0=22.8V
CALCULATION:
38
During the OFF period the inductor current cannot fall down
instantaneously, this current is forced to flow through the diode. As the
current tends to decrease, polarity of the EMF induced in L is reversed; as a
result the voltage across the source is more than the supply voltage.
PROCEDURE:
1.
Step-up chopper circuit is simulated using MATLAB simulation
software.
2.
3.
Connections are given as per the circuit diagram.
Switch ON the RPS kit and turn ON the triggering circuit.
4.
Obtain different set of reading by changing the duty cycle.
5.
Observed values are verified with the theoretical values and
simulated values.
6.
The output voltage graph is plotted for different duty cycles and
also Vo versus duty cycle
(D) graph is also plotted.
39
TABULATION:
STEPUP CHOPPER
Vs =
T=
SI.No Switch ON Period
(TON)
Duty
cycle(D)
V
s
Output Voltage(VO)
(in volts)
(ms)
Calculated Simulated
40
Observed
RESULT:
Thus the step up chopper was simulated and experimentally verified with
R Load and the output voltage waveforms are obtained for various duty
cycles.
41
CIRCUIT DIAGRAM
WAVEFORM – SQUARE WAVE INVERTER
M= Modulation Index =
- Amplitude of reference signal
- Amplitude of carrier signal
42
EX NO:
SINGLE PHASE INVERTER
DATE:
AIM:
To simulate/Implement single phase bridge inverter with various modulation
techniques namely,
1. Square wave inverter
2. Multiple pulse width modulation
3. Sinusoidal pulse width modulation using PSIM software.
APPARATUS REQUIRED:
S.NO APPARATUS
REQUIRED
1.
Psim SOFTWARE
2.
TOOL
3.
IGBT Module
4.
Inverter control module
CRO
Resistive Load
RANGE
QUANTITY
-
1
1
1
1
FORMULAE USED:
For square wave inverter ,
For multiple pulse width modulation,
where VS – Input DC
For sinusoidal pulse width modulation,
Voltage
THEORY:
1.SINGLE PULSE FULL BRIDGE INVERTER :
SQUARE WAVE INVERTER:
The Single phase full bridge inverter consists of four SCRs and full diodes
.For Full bridge inverter, when T1, T2 conduct load voltage is Vs and when T3, T4
43
SINUSOIDAL PULSE WIDTH MODULATION
MULTIPLE PULSE WIDTH MODULATION
44
conduct load voltage is –Vs. Frequency of output voltage can be controlled by
varying the period T.
2.PULSE WIDTH MODULATION TECHNIQUES:
PULSE WIDTH MODULATED INVERTERS:
PWM inverters are gradually taking over other types of inverters in industrial
applications. PWM techniques are characterized by constant amplitude pulses .The
width of these pulses is however modulated to obtain inverter output voltage control
and to reduce its harmonic content. Different PWM techniques are 1.Single pulse
width modulation.
2.Multiple pulse width modulation.
3.Sinusoidal pulse width modulation.
In PWM inverters forced commutation is essential. Three PWM techniques listed
above differ from each other in the harmonic content in their respective output
voltages. Thus choice of a particular PWM techniques depend upon the permissible
harmonic content in the inverter output voltage
MULTIPLE PULSE WIDTH MODULATION TECHNIQUES:
•
•
•
•
•
These are more than one pulse per half cycle in the mPWM.
These gate pulses are used to control the output voltage of inverter as
well as reduce the harmonic
The magnitude and width of the pulses are equal in this period
The reference signal and higher carrier frequency signals are compared
in this method in order to generate more than one gating pulse.
The number of gate pulses depend upon carrier frequency where as the
output voltage depends upon frequency of the reference signal.
SINUSOIDAL PULSE WIDTH MODULATION TECHNIQUE:
❖ The reference signal is taken as sinusoidal signal waveform where as
the carrier signal is taken as triangular waveform in this method.
❖ The width of pulse is not equal since sinusoidal wave is taken as
thereference signal
❖ The amplitude of sinusoidal waveform is not constant.
❖ The width of the gate pulses is determined by intersection point of the
sinusoidal waveform and triangular waveform.
45
TABULATION:
SQUARE WAVE INVERTER
Vs = ___ V
S.NO. T1,T2
(ms)
T3,T4
(ms)
OUTPUT VOLTAGE (V)
CALCULATED SIMULATED
MEASURED
MULTIPLE PULSE WIDTH MODULATION
OUTPUT VOLTAGE (V)
Vr(V) Vc(V) MODULATION
MEASURED CALCULATED SIMULATED
INDEX
46
❖ The frequency of inverter output voltage depends upon the frequency
of the reference signal and amplitude of the reference signal controls
the modulation index.
❖ The number of pulses per half cycle when the amplitude of triangular
waveform becomes maximum, is zero.
Np=fc/2fr , where fc = carrier wave frequency
fr= reference wave frequency
PROCEDURE:
1. Open the simulation command window.
2. Draw the circuit diagram.
3. Start the simulation and run the program
Obtain various pulse width waveforms by varying the modulation index of the circuit
SINGLE PHASE SINUSOIDAL PWM INVERTER:
47
SINUSOIDAL PULSE WIDTH MODULATION
OUTPUT VOLTAGE (V)
Vr(V) Vc(V) MODULATION
MEASURED CALCULATED SIMULATED
INDEX
SINGLE PHASE SQUARE WAVE PWM INVERTER:
OUTPUT:
SINGLE PULSE/(SQUARE WAVE) WIDTH MODULATION:
48
MULTIPLE PULSE WIDTH MODULATION:
RESULT:
49
THREE PHASE BRIDGE INVERTER:
MODEL GRAPH – 1800 CONDUCTION MODE:
50
EX NO:
THREE PHASE INVERTER
DATE:
AIM:
To study/implement the operation of three phase inverter in both
PSIM/MATLAB simulation.
APPARATUS REQUIRED:
➢ PSIM simulation tool
➢ Three phase inverter module
➢ CRO
FORMULA USED:
180o conduction mode:
Phase Voltages
a) For 0≤ ɷt ≤ π/3
Van=Vcn=Vs/3;
Vbn= -2Vs/3
b) For π/3≤ ɷt ≤2π/3
Van=2Vs/3;
Vbn= Vcn= -Vs/3
c) For 2π/3≤ ɷt ≤ π
Van= Vbn= Vs/3; Vcn= -2Vs/3
Line to Line RMS voltage: VL= √(2/3) Vs =0.8165Vs
Line-to-line neutral RMS voltage: Vp= VL/√3
120o conduction mode:
Phase Voltages
d) For 0≤ ɷt ≤ π/3
Van= Vs/2
Vbn=- Vs/2
Vcn=0
Vbn=0
Vcn=- Vs/2
e) For π/3≤ ɷt ≤2π/3
Van= Vs/2
For 2π/3≤ ɷt ≤ π
Van=0
Vbn= Vs/2
51
Vcn=- Vs/2
1200 CONDUCTION MODE :
TABULATION:
MODE OF
OPERATION
Vph (RMS)
(RMS)
Simulated Calculated Simulated Calculated Practical
(v)
(v)
(v)
(v)
(v)
52
RMS value of phase voltage: Vp = Vs/√6
RMS value of Line voltage:
VL=√3Vp = 0.7071Vs
THEORY:
A 3ϕ bridge inverter power circuit using six thyristors and six diodes, which is used
to supply 3ϕ load (star connected or delta connected).
3ϕ 180 DEGREE CONDUCTION MODE:
➢ A maximum of 3 SCR’s conduct at any instant and each SCR conducts for π
radians in every part of output.
➢ SCR pair in each leg ie.) T1, T4 ; T3,T6 ; T5,T2 are turned on with a time
interval 1800 ie, SCR T1 conducts for 1800 and T4 for 1800 of a cycle.
➢ The upper group SCR’s T1, T3, T5 conducts at an interval of 1200 .
INTERVAL THYRISTORS
CONDUCTING
I
T1, T6, T5
II
T1, T6, T3
III
T1, T2, T3
IV
T4, T3, T2
V
T4, T3, T5
VI
T4, T6, T5
3ϕ 120 DEGREE CONDUCTION MODE:
➢ Here each of the SCR conducts for 1200 at any instant of time, only two
SCR’s remain on.
➢ Like 1800 mode, 1200 mode inverter also requires six steps each of 600
duration.
INTERVAL
THYRISTORS
CONDUCTING
I
II
III
IV
V
VI
T1 , T6
T1 , T2
T3 , T2
T3 , T4
T5 , T4
T5 , T6
53
MODEL CALCULATION:
54
RESULT:
55
CIRCUIT DIAGRAM:
TABULATION:
R LOAD
Vₛ=
S.NO
FIRING
ANGLE(α)
(degrees)
OUTPUT VOLTAGE(Vo)
(volts)
CALCULATED
1
2
3
4
56
OBSERVED
EX NO:
DATE:
THREE PHASE FULLCONVERTER
AIM:
To simulate the three phase full converter with R load and also to obtain the
corresponding voltage and current waveforms for various firing angles.
APPARATUS REQUIRED:
1. Desktop Computer with Pentium Processor.
2. MATLAB Software.
FORMULA USED:
1.For R load with 0 ≤ α ≤ 60:
•
Va = (3Vm/л)*cosα
•
Vm = √2Vs
•
Ia = V a / R
For R load, α ≤ 60 (Discontinuous conduction)
•
Where,
Va = (3Vm/π)* (1 + cos (α+(π/3)))
Va
Vm
α
= Average output voltage in volts
= maximum input line voltage in
volts.
= Delay or Firing angle in
degrees.
57
SIMULATION:
THREE PHASE FULL CONVERTER WITH R LOAD:
OUTPUT:
58
THEORY:
(i) CONVERTER OPERATION:
FOR FIRING ANGLE = O DEGREE:
A three phase full converter produces fewer ripples in the output than the
single phase full converter. Here the thyristors are triggered in the following
sequence T1, T2, T3, T4, T5, T6.
At ωt=30˚, thyristor T1 becomes eligible to conduct. Thyristor T1 starts to conduct
at ωt=30˚+α after it is fired. T1 and T6 conduct and the output voltage V0=Vab. At
ωt=90˚+α, thyristors T2 is triggered and now T1 and T2 conduct until T3 is
triggered and the output voltage is V0=Vab. Each thyristor pair conducts for 60˚.
There are six segments in the output voltage. If the load is inductive and if α>60˚,
the output voltage has negative segments. The frequency of ripple in the output is
6fs, where fs is the supply frequency.For a phase angle of upto 30˚, the ’c’ phase
winding is more positive than ‘a’ phase winding. Because of that, the thyristor in ‘a’
phase is reverse biased. If we apply the firing angle for thyristor T1, during this
period it will not conduct. Hence the delay angle for the thyristor T1 is measured
from ωt=30˚ of line voltage.
INVERTER OPERATION:
When the firing angle α is more than 90°, the dc output voltage will be
negative. It is only possible to commutate current from, say thyristor T1 to T2 while
the instantaneous voltage of phase B is higher than phase A. At firing angle,
α=180°, EB=EA and the relative voltage between the two phases after this reverses,
making commutation impossible, hence α=180° is the limit of operation.
PROCEDURE:
1. Open the simulink model. Select new file from the menu.
2. Model for the three phase fully controlled converter is made as per the circuit
diagram.
59
. MODEL CALCULATION:
60
3. The model is simulated for the firing pulse α=0°. The line voltage leads
the phase voltage by 30°. The firing pulse is measured from 60° of phase voltage
(Since T1 is forward biased only after 30° of ‘A’ phase voltage).
4.The output voltage and current waveform are measured.
RESULT:
Thus the three phase full converter was simulated with R Load and the output
voltage and current waveforms are obtained for various firing angles.
61
CIRCUIT DIAGRAM OF TRIAC
MODEL GRAPH:
VI CHARACTERISTICS OF TRIAC
62
EX NO:
V-I CHARACTERISTICS OF TRIAC
DATE:
AIM:
To obtain the forward and reverse conduction characteristics of the given
TRIAC also find the latching and holding currents of the given TRIAC.
APPARATUS REQUIRED:
S.No Name of the Application
Type
1.
TRIAC
BT136
2.
Resistor
Carbon
3.
Power Supply
4.
Resistor
5.
Bread Board
6.
Connecting Wires
Carbon
Range
Quantity
1
1kΩ
1
(0-30)V
2
470Ω
1
1
Single Turn
1 / 18
Range
THEORY:
The TRIAC is a four layer three terminal semiconductor device. The
terminals are anode, cathode and gate. Anode is always at a higher positive potential
than the cathode. When the applied potential is increased the forward bias at the
outer layer and the reverse at the inner layer increasing avalanche multiplication.
The potential at which the break down occurs is known as breaking or firing
potential.
A voltage applied at the gate terminal can control the break down voltage. The gate
terminal is forward biased with respect to cathode. The gate terminal is used to
control turn on to TRIAC. Once the TRIAC is turn on, the gate looses control.
63
TABULATION:
MT1 is + ve with respect to MT2
S.No
IG1=
IG2=
IG3 =
VAK
VAK(V)
IA(mA)
(V)
IA(mA)
VAK(V)
1
2
3
4
5
MT2 is + ve with respect to MT1
IG1 =
IG2 =
IG3 =
S.NO.
VAK(V)
IA(mA)
VAK(V)
1
2
3
4
5
64
IA(mA)
VAK(V)
IA(mA)
IA(mA)
PROCEDURE:
➢ Connections are made as per the circuit diagram with MT1 +Ve with
respect to
MT2.
➢ Switch on the 230V AC supply through three-pin power chord.
➢ Keep the gate current (IG) to a suitable value (say minimum of 4 mA to
5mA)
➢ Now slowly increase the anode-cathode voltage (VAK) by varying the
pot till Triac get turned on, with the indication that anode cathode
voltage decreases to it’s on state voltage drop (i.e 0.7V) and the anode
current increases.
➢ Note the values of voltmeter (VAK) which is the break over voltage and
the ammeter (I L) which is the latching current value.
➢ Further, increase the anode current in steps by varying the anode-
cathode voltage and note the readings.
➢ Now reduces the anode cathode voltage (VAK) till the triac turned off
and find the
holding current.
➢ For various gate current take the readings and tabulate it.
➢ Connect MT2 terminal of Triac is + Ve with respect to MT 1
➢ Repeat the same procedure from 2 to 8
➢ Finally, a graph of anode current Vs anode-cathode voltage is plotted
for various gate current for forward and reverse biases.
RESULT:
65
CIRCUIT DIAGRAM:
WAVEFORMS:
66
EX NO:
1-PHASE AC VOLTAGE CONTROLLER WITH R-LOAD
DATE:
AIM:
To study the performance of a single phase AC Voltage controller with R load.
APPARATUS REQUIRED:
1. Power Electronics Trainer Kit
2. Firing Circuit
3. CRO
FORMULAE REQUIRED:
THEORY:
In the period 0 < t< π/ω; The SCR T1 is forward biased and SCR T2 is reverse
Biased .Let the T1 be triggered at an angle of α (0<α<π/ ω).Then the supply
terminals are connected to the load through T1 and the current starts flowing
through the load via SCR. Therefore the supply appears across the load. During the
period (π/ω<t<2π/ω) T1 is reverse biased and T2 is forward biased and when we
give trigger pulse at an angle of (π+α) /ω, [0< (π+α)/ω <2π/ω] T2 starts conducting
and the load terminals are connected to supply through T2 hence the output voltage
is the supply voltage from the instant of triggering. This repeats for the every half
cycle.
PROCEDURE:
1. Connect the circuit as shown in the circuit diagram.
2. Give the firing pulses accordingly at a suitable firing angle from the firing circuit.
3. Observe the load voltage on the CRO and note down the firing angle.
4. Draw the waveforms and calculate the RMS value of output voltage.
67
TABULATION
S.NO. TRIGGER
ANGLE
V0
(RMS)
TRIGGER
ANGLE
(IN
(IN
DEGREES) RADIANS)
SIMULATED PRACTICAL CALCULATED
(V)
(V)
(V)
MODEL CALCULATION:
68
RESULT:
69
CIRCUIT DIAGRAM:
MODEL GRAPH:
70
EX NO:
DATE:
STEP UP DOWN CHOPPER
AIM:
To simulate the step up down chopper with R load and also obtain the
corresponding voltage waveform for various duty cycle and verify experimentally.
APPARATUS REQUIRED:
1)
2)
3)
4)
Desktop/laptop with matlab software.
Step up down chopper
CRO
Multimeter.
FORMULA USED:
Vₒ =Vₛ * D/(1-D)
D= Tₒₙ/ T
T=1/fₛ
T= Tₒₙ+Toff
D-Duty cycle; fₛ-Switching frequency; T-Total time.
PROCEDURE:
1)
2)
3)
4)
5)
Step up down chopper circuit is simulated using matlab.
Connections are given as per the circuit diagram.
Switch on the RPS kit and turn on the triggering control.
Obtain the different set of reading by changing the duty cycle.
Observed values are verified with the simulated and calculated
value.
6) The output voltage graph is plotted for different duty cycles and
also Vₒ vs duty cycle(D) graph is plotted.
71
TABULATION:
S.No
Time Period
(T)
Output Voltage (Vₒ)
Duty Cycle
(D)
Calculated
72
Simulated
volts
Observed
SIMULATION CIRCUIT:
OUTPUT:
RESULT:
The output waveform of the step up down chopper is obtained.
73