Download Single Phase Half Wave Rectifier with R

Single Phase Half Wave Rectifier with R & RL load
Aim:
To simulate the 1ϕ half controlled rectifier circuit with R & RL load and obtain the corresponding
waveforms using MATLAB/SIMULINK.
Formulae Used:
V
Average DC Voltage, Vdc  m 1  cos  Volts

1
V
2
RMS output voltage, V rms  m      sin 2
Volts
2
2

Average Output Current, I dc 

Vdc
Ampere
R
Vrms
Ampere
R
where, Vm is the maximum input voltage
 is the firing angle of the SCR.
Operation:
The phase controlled rectifiers using SCRs are used to obtain controlled dc output voltages from the fixed
ac mains input voltage. The circuit diagram of a half controlled converter is shown in Figure 1. The
output voltage is varied by controlling the firing angle of SCRs. The single phase half controlled
converter consists of two SCRs and two diodes. During positive half cycle, SCR1 and Diode 2 are
forward biased. Current flows through the load when SCR1 is triggered into conduction. During negative
half cycle, SCR3 and Diode1 are forward biased.
If the load is resistive, the load voltage and load current are similar. If the load is inductive, the current
will continue to flow even when the supply voltage reverses polarity due to the stored energy in the
inductor. At the end of positive half cycle, D2 is reverse biased and D1 is forward biased. As SCR1 is not
turned off the freewheeling current due to the stored energy in the inductor will flow through the diode
D1 and SCR1. When SCR3 is triggered, the current gets transferred from SCR1 to SCR3. Load current
now flows from supply via SCR3, load and D4. At the end of negative half cycle, the freewheeling
current will flow through the diode D2 and SCR3.
RMS Output Current, I rms 
Circuit Diagram:
With Resistive Load:
Waveforms:
With inductive load:
Waveforms:
Result:
Thus the Single Phase half controlled Rectifier with R & RL Load circuit is simulated using
MATLAB/SIMULINK and the corresponding waveforms are obtained.
SIMULATION OF SINGLE PHASE FULL CONVERTER
AIM:
To simulate single Phase Full Converter circuit with R load in MATLAB - SimuLink.
APPARATUS REQUIRED:
A PC with MATLAB package.
THEORY:
SINGLE PHASE FULL CONVERTER
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. Figure 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, and 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.
The Fig-3, shows the current and voltage waveforms for this circuit. For large power dc loads, 3phase ac to dc converters are commonly used. The various types of three-phase phase-controlled
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 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 3- phase converters are used, is
therefore superior as compared to when single-phase converters are used.
2
Output Voltage, Vout  VS cos

Vavg
Average Current, I avg 
R
Circuit Diagram:
OUTPUT WAVEFORMS:
Set AC Input Parameter
(Peak amplitude =100 V, Phase=0 deg and Frequency=50 Hz)
Set Pulse generator Parameter
(First pulse generator period=0.02 sec, Pulse width=50% and Phase delay=0.002 sec)
(Second pulse generator period=0.02 sec, Pulse width=50% and Phase delay=0.012 sec)
RESULT:
Thus the simulation of single phase Full converter model is done and the output is verified using
MATLAB Simulink.
Three Phase Fully controlled Rectifier with R & RL Load
Aim:
To simulate the 3Ø fully Controlled rectifier circuit with R & RL load and obtain the
corresponding waveforms using MATLAB/SIMULINK
Theory:
The three phase full bridge converter works as three phase AC-DC converter for firing angle
delay 00<α≤900 and as three phase line commutated inverter for 900<α<1800. The numbering of
SCRs are 1, 3, 5 for the positive group and 2, 4, 6 for negative group. This numbering scheme is
adopted here as it agrees with the sequence of gating of six thyristors in a 3-phase full converter.
Here each SCR is conduct for 120o. At any time two SCRs, one from positive group and
other from negative group must conduct together and this combination must conduct for 60 o. This
means commutation occurs for every 60o. For ABC phase sequence of three phase supply
thyristors conduct in pairs: T1 and T2, T2 and T3, T3 and T4, T4 and T5, T5 and T6, T6 and T1.
Formulae Used:
Average Output Voltage, V0  3
Vml

cos
1
RMS value of output voltage, Vo,rms  Vml
3
2

2
  3 cos 2 
3 2



2
3
o
o
Each SCR conducts for 120 for every 360 . Therefore the RMS value of SCR current is,
RMS of the source current, I s  I 0
IT  I 0
1
3
Circuit Diagram:
Model Graph:
Resistive Load:
Inductive Load:
Result:
Thus the three phase fully controlled Rectifier with R & RL Load circuit is simulated using
MATLAB/SIMULINK and the corresponding waveforms are obtained.
SINGLE PHASE AC VOLTAGE REGULATOR
Aim:
To simulate the 1Ø AC voltage regulator circuit and obtain the suitable waveforms using
MATLAB/SIMULINK
Theory:
AC regulators are used to get variable AC voltage from the fixed mains voltage. Some of the important
applications of AC regulators are: domestic and industrial heating, induction heating in metallurgical
industries, induction motor speed control for fan and pump drives, transformer tap changers in utility
systems, static reactive power compensators, lighting control etc., Earlier, auto transformers, transformers
with taps and magnetic amplifiers were employed in these applications because of high efficiency,
compact size, flexibility in control etc. Two thyristors in anti parallel are employed for full wave control.
In this case, isolation between control and power circuit is most essential because of the fact that the
cathodes of the two thyristors are connected to the common point. For low power applications, a triac
may be used. In this case isolation between control and power circuitry is not necessary.
Formulae Used:
The triggering pulse is generated at the point at which the associated cosine wave becomes
instantaneously equal to the control voltage.
V R  2V sin   t 
At this instant, t= and hence,
VR  2V sin    
 VR 

 2V 
Where, VR- breakdown voltage of the Diac
- firing angle delay
V- Supply voltage
Circuit Diagram:
    sin 1 
OUTPUT WAVEFORMS:
Set AC Input Parameter
(Peak amplitude =100 V, Phase=0 deg and Frequency=50 Hz)
Set Pulse generator Parameter
(First pulse generator period=0.02 sec, Pulse width=50% and Phase delay=0.003 sec)
(Second pulse generator period=0.02 sec, Pulse width=50% and Phase delay=0.013 sec)
Operation:
A triac control circuit for lamp dimmers is shown in Fig.1. A diac is a gateless triac designed to
breakdown at a low voltage. During the positive half cycle, the triac requires a positive gate
pulse for turning it on. This is provided by the capacitor C. When its voltage is above the
breakdown voltage of the diac, the capacitor C discharges through the triac gate. When the triac
turns on, the capacitor Voltage will be reset to zero. A similar operation takes place in the
negative half cycles, and a negative gate pulse will be applied when the diac breaks down in the
reverse direction. Adjustment of series resistance, R determines the charging rate of capacitor C
and hence the value of the phase angle delay. The output power and thus light intensity are
varied by controlling the phase of conduction of the triac.
Model Graph:
Result:
Thus the 1ϕ AC Voltage regulator with R load circuit is executed with the help of MATLAB software
and the graph is plotted.
SIMULATION OF DC-DC CONVERTERS
AIM:
To simulate DC-DC Converter circuit with R load in MATLAB - SimuLink.
APPARATUS REQUIRED:
A PC with MATLAB package.
THEORY:
DC-DC BOOST CONVERTER
OUTPUT WAVEFORMS:
DC-DC BOOST CONVERTER
Set DC Input Parameter (Amplitude =12 V)
Set Inductor Parameter (Inductance=0.1 H)
Set Pulse generator Parameter (Period=10e-6 sec, Pulse width=50% and Phase
delay=0 sec)
DC-DC BUCK CONVERTER
DC-DC BUCK CONVERTER
Set DC Input Parameter (Amplitude =12 V)
Set Pulse generator Parameter (Period=10e-6 sec, Pulse width=50% and Phase
delay=0 sec)
In this circuit, the transistor is either fully on or fully off; that is, driven between the extremes of
saturation or cutoff. By avoiding the transistor's active" mode (where it would drop substantial voltage
while conducting current), very low transistor power dissipations can be achieved. With little power
wasted in the form of heat, Switching" power conversion circuits are typically very efficient. Trace all
current directions during both states of the transistor. Also, mark the inductor's voltage polarity during
both states of the transistor.
RESULT:
Thus the simulation of dc-dc converters (Buck
and the output is verified using MATLAB Simulink.
and
Boost
Converter)
model
is
done