EXPERIMENT NO-6
AIM OF THE EXPERIMENT:-
Simulation of single phase semiconverter (i)symmetric,(ii)asymmetric with R,RL and RLE load
and do FFT analysis and find THD.
SOFTWARE USED:-
MATLAB
SIMULATION BLOCKS REQUIRED:-
Single Phase AC voltage source
Thyristor
Diode
Series RLC branch
DC Voltage Source
Ground
Powergui
Scope
Display
Current measurement block
Voltage measurement block
THD block
Mean block
RMS block
THEORY:
Single Phase Semi Converter is also known as a half-controlled converter. A single-
phase half controlled or semi converter utilizes SCRs(thyristor) and diodes to convert
AC power to DC power. Due to the utilization of diodes and thyristors, it provides
limited control over the level of DC output voltages.it operates in two modes
(i)symmetric mode
(ii)asymmetric mode
in semiconverter we use two diodes and two thyristors .in symmetric mode one diode
and one thyristor is connected in each leg.in asymmetric mode one leg contain two
thyristor and other leg contain two diode.thecircuit diagram of symmetric mode is
Here the free wheeling diode is connected so that the energy stored in the inductor is
again fed back to the r load during the discharge of the L load.
The diagram for asymmetric mode is
Consider highly inductive load and same firing angle α . Let γT = conduction angle of
thyristor and γD = conduction angle of diode in period of 2π.
In case of symmetric model the conduction angle for both the diode and thyristor is
same and is equal to π.
In case of asymmetric model the diode conduction time is π+ α and thyristor conduction
time is π- α.
1. average and RMS thyristor current in symmetrical configuration is higher. So
SCR current rating should be higher in symmetrical configuration.
2. average and RMS diode current in asymmetrical configuration is higher. So
diode current rating should be higher in asymmetrical configuration.
SIMULATION DIAGRAM(SYMMETRIC MODE):-
Simulation circuit diagram for R load
Scope analysis of the 1-phase semiconverter(symmetric) with R load
Simulation circuit diagram for RL load
Scope analysis of the 1-phase semiconverter(symmetric) with RL load
FFT analysis with RLE load
Simulation circuit diagram for RLE load
Scope analysis of the 1-phase semiconverter(symmetric) with RLE load
FFT analysis with RLE load
ASYMMETRIC MODE:-
Simulation circuit diagram for R load
Scope analysis of the 1-phase semiconverter(assymetric) with R load
Simulation circuit diagram for RL load
Scope analysis of the 1-phase semiconverter(assymetric) with RL load
FFT analysis with RL load
Simulation circuit diagram for RLE load
Scope analysis of the 1-phase semiconverter(assymetric) with RLE load
FFT analysis with RLE load
OBSERVATION:-
SYMMETRIC MODE
load α R (Ω) L E (V) RMS Mean Form Ripple THD
(°) (H) Voltage Voltage Factor Factor (%)
(V) (V)
R Load 30 10 - - 68.21 57.78 1.18 0.626 -
RL Load 30 10 0.1 - 68.2 57.63 1.183 0.631 27.09
RLE Load 30 10 0.1 10 68.56 58.24 1.177 0.62 28.52
ASYMMETRIC MODE
load α R (Ω) L E (V) RMS Mean Form Ripple THD
(°) (H) Voltage Voltage Factor Factor (%)
(V) (V)
R Load 30 10 - - 68.21 57.78 1.18 0.626 -
RL Load 30 10 0.1 - 68.2 57.63 1.183 0.631 27.09
RLE Load 30 10 0.1 10 68.56 58.24 1.177 0.62 27.32
INFERENCE:-
In the above experiment we studied about the output wave form of single
phase semi-converter(symmetric and asymmetric) with R, RL and RLEload.
In ths semi-converter we have used two thyristors and two diodes.By simply
varying the gate pulse of thyristor we can control the output of the device.
RMS and average value was calculated for different loads R,RL,RLE.
Durgadutta das
1901106296
Electrical
A2
EXPERIMENT NO-7(1)
AIM OF THE EXPERIMENT:-
Simulation of three phase full controlled rectifier with R ,RL and RLE load and do the FFT
analysis and find the THD.
SOFTWRE USED :
MATLAB
SIMULATION BLOCKS REQUIRED:
Three Phase AC voltage source
Thyristor
Pulse generator
Series RLC branch
DC Voltage Source
Powergui
Scope
Display
Current measurement block
Voltage measurement block
THD block
Mean block
RMS block
Divide block
Function block
THEORY:-
A three phase fully controlled converter is obtained by replacing all the six diodes of an
uncontrolled converter by six thyristors. For any current to flow in the load at least one
device from the top group (T1, T3, T5) and one from the bottom group (T2, T4, T6) must
conduct.
From symmetry consideration it can be argued that each thyristor conducts for 120° of the
input cycle. Now the thyristors are fired in the sequence T1 → T2 → T3 → T4 → T5 → T6 →
T1 with 60° interval between each firing. Therefore thyristors on the same phase leg are
fired at an interval of 180° and hence cannot conduct simultaneously.
This leaves only six possible conduction mode for the converter in the
continuous conduction mode of operation. These are T1T2, T2T3, T3T4, T4T5,
T5T6, T6T1. Each conduction mode is of 60° duration and appears in the
sequence mentioned.
For example the thyristor T1 is fired at the end of T5T6 conduction interval.
During this period the voltage across T1 was vac. Therefore T1 is fired α angle
after the positive going zero crossing of vac. To arrive at the waveforms it is
necessary to draw the conduction diagram which shows the interval of
conduction for each thyristor and can be drawn with the help of the phaser
diagram.
If the converter firing angle is α each thyristor is fired “α” angle after the
positive going zero crossing of the line voltage with which it’s firing is
associated. Once the conduction diagram is drawn all other voltage
waveforms can be drawn from the line voltage waveforms and from the
conduction.
Similarly line currents can be drawn from the output current and the
conduction diagram. It is clear from the waveforms that output voltage and
current waveforms are periodic over one sixth of the input cycle. Therefore
this converter is also called the “six pulse” converter. The input current on
the other hand contains only odds harmonics of the input frequency other
than the triplex (3rd, 9th etc.) harmonics.
SIMULATION DIAGRAM:-
3 phase full controlled rectifier with R load
3 phase full controlled rectifier with RLE load
3 phase full controlled rectifier with RLE load
Plots:-
Scope analysis of the 3-phase full controlled rectifier with R load
Scope analysis of the 3-phase full controlled rectifier with RL load
Scope analysis of the 3-phase full controlled rectifier with RLE load
FFT ANALYSIS:-
FFT analysis for 3-phase full controlled rectifier with R load
FFT analysis for 3-phase full controlled rectifier with RL load
FFT analysis for 3-phase full controlled rectifier with RLE load
OBSERVATION:-
α R (Ω) L E (V) RMS Mean Form Ripple THD
(°) (H) Voltage Voltage Factor Factor (%)
(V) (V)
R Load 30 10 - - 116.4 114.4 1.018 0.191 65.09
RL Load 30 10 0.1 - 116.4 114.4 1.018 0.191 30.75
RLE Load 30 10 0.1 40 116.4 114.4 1.019 0.189 30.82
INFERENCE:-
In the above experiment we simulated 3-phase full controlled rectifier with R,RLand RLE
load.
The voltage across the load doesn”t change much with the load.
It is always a 6 pulse converter for any firing angle.the dc current obtained is smooth and it
contains less ripple.
Durgadutta das
1901106296
Electrical
A2
EXPERIMENT NO-7(2)
AIM OF THE EXPERIMENT:-
Simulation of three phase semi converter with R ,RL and RLE load and do the FFT
analysis and find the THD.
SOFTWRE USED :
MATLAB
SIMULATION BLOCKS REQUIRED:
Three Phase AC voltage source
Thyristor
Diode
Pulse generator
Series RLC branch
DC Voltage Source
Powergui
Scope
Display
Current measurement block
Voltage measurement block
THD block
Mean block
RMS block
Divide block
Function block
THEORY:-
Figure shows the circuit diagram of three phase semi converter supplying an R-L-E
load. The output voltages Vo across load terminals is controlled by varying the firing
angles of SCRs T1, T2 and T3. The diodes D1, D2 and D3 provide merely a return path
for the current to the most negative line terminal. At any instant thyristor
connected to most positive line terminal and diode connected to most negative line
terminal conducts. For 0≤α≤π/3 each diode and thyristor conduct for 2π/3 radians. The
freewheeling diode does not conduct for α<π/2. The freewheeling diode conducts for
π/6 radians in each pulse when α=π/2. For α≥π/2, when output voltage tends to
become negative freewheeling diode become forward biased which makes output
voltage zero. The output voltage thus never becomes less than zero in the case of
three phase semi converter supplying an R-L-E load .The output voltage is
discontinuous when firing angle α=π/2,2π/3.The output current is discontinuous for
α=2π/3.For α=2π/3 when all the energy stored in inductance is discharged diode stops
conducting and as a result, load voltage rises to load countermen E.A three phase semi
converter has the unique feature of working as a six-pulse converter for α<π/3 and as
a three-pulse converter for α≥ π/3.Average output voltage for three phase
countermen α<π/3isV0=(3Vml(1+cos α))/2πWhere α=firing angle of
countermen=maximum value of line-line voltage.
SIMULATION DIAGRAM:-
Simulation circuit diagram for R load
Simulation circuit diagram for RL load
Simulation circuit diagram for RLE load
PLOTS:-
Scope analysis of the 3-phase semi converter with R load
Scope analysis of the 3-phase semi converter with RLE load
Scope analysis of the 3-phase semi converter with RLE load
FFT analysis:-
FFT analysis of R load
FFT analysis of RLE load
FFT analysis of RLE load
OBSERVATION:-
α R (Ω) L E (V) RMS Mean Form Ripple THD
(°) (H) Voltage Voltage Factor Factor (%)
(V) (V)
R Load 30 10 - - 126.4 125.5 1.245 0.142 30.82
RL Load 30 10 0.1 - 126.4 125.5 1.245 0.142 42.82
RLE Load 30 10 0.1 20 126.4 125.5 1.245 0.142 42.31
INFERENCE:-
Semiconverter only acts as a rectifier unlike fully controlled converter which act both
as converter and rectifier.
In case of three phase semi converter the thd of source current is less as compared to
the fully controlled rectifier.
Durgadutta das
190106296
Electrical
A2
