Power Electronics Tutorials (EEEP2204)

Electrical and Electronic Engineering - EEE

Semester: Second Semester

Level: 200

Year: 2016

Answers (200 )
TUTORIALS POWER ELECTRONICS
Tutorial 1
A half-wave single phase uncontrolled rectifier has a pure resistive load R=10. The input is
connected to a 285 V peak - 50Hz AC voltage.
1.1. Draw the corresponding diagram
1.2. Draw the waveforms of the load voltage and the voltage across the diode.
1.3. Calculate the average load voltage (V
dc
) and the average load current (I
dc
)
1.4. Calculate the rms load voltage (V
rms
) and the rms load current (I
rms
)
1.5. Calculate the efficiency of the rectifier (η)
1.6. Calculate the form factor (FF)
1.7. Calculate the ripple factor (RF)
1.8. What is the peak inverse voltage (PIV) of the diode?
Tutorial 2
Let's consider a full-wave center-tap diode rectifier with a purely resistive load R=100. The primary
voltage is 230V-50Hz and the transformation ratio k =0.02174
2.1. Draw the corresponding diagram
2.2. Draw the waveforms of the load voltage and the voltage across each diode.
2.3. Calculate the rms value of the secondary voltages (V
s2-rms
).
2.4. Calculate the efficiency (the rectification ratio)
2.5. Calculate the form factor (FF)
2.6. Calculate the ripple factor (RF)
2.7. What is the peak inverse voltage (PIV) of one diode?
Tutorial 3
Let’s consider a full-wave diode bridge rectifier with a pure resistive load R=15. connected to an
AC supply voltage v
s
(t)=300sin(314 t) using a transformer of unity transformation ratio.
3.1. Draw the corresponding diagram
3.2. Draw the waveforms of the output voltage and the voltage across one diode
3.3. Calculate the efficiency (the rectification ratio)
3.4. Determine the form factor (FF)
3.5. Determine the ripple factor (RF)
3.6. What is the peak inverse voltage (PIV) of one diode?
3.7. Calculate the input power factor
3.8. Regarding the previous rectifier, what are the main advantages of this circuit?
Tutorial 4
Let's consider the rectifier of Tutorial 3 connected to a pure DC load of I
0
=30A.
4.1. Draw the corresponding diagram
4.2. Draw the waveforms of the load voltage (v
1
), (he load current (i
L
) and a diode current (i
di
)
4.3. What is the average value (I
dc
) and rms value (I
rms
) of the load current?
4.4. Calculate the average value (V
dc
) and the rms value (V
rms
) of the load voltage.
4.5. Deduce the efficiency of the circuit.
4 6 Determine the form factor (FF)
4.7. Determine the ripple factor (RF)
4.8. Determine the PIV of each diode.
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4.9 Determine the input power factor if the rms value of the fundamental input current is given by the
expression: I
sl
=4I
0
/
√
2. NB: for non-sinusoidal current, PF=V
s
I
sl
cos / V
s
I
s
Tutorial 5
Let's consider a half-wave three-phase uncontrolled rectifier operating from 460 V-50 Hz supply at
secondary side of a ∆-Y coupled transformer and a load resistance of R=20 Ω. If the source
inductance is negligible,
5.1. Draw the corresponding diagram
5.2. Determine the peak value of a secondary voltage
5.3. Calculate the average value (V
dc
) and the rms value (V
rms
) of the load voltage.
5.4. Determine the form factor (FF)
5.5. Determine the ripple factor (RF)
5.6. What is the PIV of each diode?
Tutorial 6
A single phase controlled rectifier supply a pure resistive load R=50Q, the AC voltage has the
following characteristics: 220V-50Hz. The Thyristor firing angle is a.
6
.
1
. Draw the corresponding diagram and the waveform of the load voltage
6
.
2
. From the waveform, give the expression of the average load voltage (V
dc
) and the rms load voltage
(V
mis
) as functions of the firing angle a.
6.3. Express the efficiency of the system as a function of .
6.4. For which value of a do we have a maximum efficiency?
6.5. For which value of a do we have a minimum efficiency?
6
.
6
. Express the form factor (FF) and the ripple factor (RF) as a functions of a
6.7. For = /4, calculate the average and rms values of the load voltage and load current.
6.8.
Deduce the corresponding efficiency.
Tutorial 7
A battery with the following characteristics: E = 12V, negligible internal resistance is charged using a
4-diodes bridge rectifier connected to the secondary of a step-down transformer. The primary is
supplied with a 220V-50 Hz AC voltage. The battery is protected with a resistance R.
7.1 Draw the corresponding diagram and plot the waveform of the load voltage
7.2. Express the conduction angle of each diode as a function of the secondary voltage Vs.
7.3
What is the value of the secondary voltage for a conduction time of t=T/4. For t=T/4.
7.4. Calculate the value of R necessary to have a maximum load-current of 10A
7.5. Draw the curve of i
L
vs. θ.
7.6. Give the expression of the average load current as a function of the conduction angle δθ
7.7. Calculate the average value of the load current and deduce the charging time if the capacity of
the battery is 100Ah.
7.8. Calculate the rms value of the load current.
7.9. Deduce the efficiency of the system.
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Tutorial 8
Let's consider the following system
The rectifier is supplied by a 230V-50Hz network. The thyristors are considered as ideal electronic
switches. The thyristors and Th
4
on one side, Th
2
and Th
3
on the other side are controlled
simultaneously with a tiring angle . We admit that the load current is ripple free because of the
presence of the inductance L.
8.1. For a=7t/3, draw the synchronized following curves and indicate the conducting thyristors.
8.1.1. The load voltage
8.1.2. The currents I
Th1
and I
Th2
8.1.3. The input current.
8.2. Give the expression of the load voltage as a function of the firing angle a.
8.3. Which type of functioning do we obtain for > /2 with a constant load current Io ?
8.4. For = /3 and Io=40A, calculate :
8.4.1 The average output voltage (V
dc
)
8.4.2 The power (P) absorbed by the motor
8.4.3 The rms value (I
s
) of the input current
8.4.4 The apparent power (S) of the system
8.4.5 The power factor of the system
Tutorial 9
A 4-diodcs bridge rectifier is used to charge 4 batteries connected in series. Each of them has the
following characteristics: 6V -50Ah. The primary of the transformer is connected to a 220V- v. I.
Draw the corresponding electric circuit of the system.
9.1. Draw the waveform of the load voltage and the load current.
9.2. Knowing that the transformation ratio of the transformer is k= 0.11818, calculate the rms value
of the secondary voltage.
9.3. What is the conduction angle of each diode?
9.4. Calculate the value of the protective resistance R.
9.5. Calculate the average value of the current in one diode.
9.6. Calculate the charging time of the battery.
9.7. What is the peak inverse value (PIV) of one diode.
9.8. Calculate the rms value of the load current.
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