APRIL 2012
ANALYSIS OF POWER ELECTRONIC CONVERTERS
1. What is the principle of operation of
cyclo converters? What is the effect of load inductance on the performance of
cyclo converter?
2. The load of an ac voltage controller is
resistive, with R = 1.5Ω. The input voltage is 120V (rms), 60 Hz. Plot the PF
against the delay angle for single phase half wave and full wave controllers.
3. Explain the operation of a three –
phase, full converter with inductive load using necessary circuit diagram and
wave forms.
4. Using neat circuit diagrams and
necessary wave forms, explain the operation of Buck regulators. And also derive
the necessary condition for continuous inductor current and capacitor voltage.
5.a) Explain the principle of operation of
a single phase half bridge inverter with Resistive load.
b) The single phase, half - bridge inverter
has a resistive load of R = 2.4 and the input voltage VΩs = 48V.
Determine
i) RMS output
voltage. ii) Output power
iii) Average and
peak currents of each thyrister. iv) The THD
v) Distortion
Factor.
6.a) Explain the operation of twelve pulse
converter.
b) A three phase full converter is operated
from a three – phase, 230V, 60Hz supply. The load is highly inductive and the
average load current is Ia = 150A with negligible ripple. If the
delay angle is α = 600 Determine the ratings of thyristors.
7.a) Explain in detail the space vector
Modulation.
b) What are the advantages of space vector
Modulation?
8. Write a short notes on the following.
a) Sinusoidal PWM
b) Multi output boost converters
c) Delta Modulation.
April 2011 NR r09
ANALYSIS OF POWER ELECTRONIC CONVERTERS
1. a) Explain the
operation of 1-φ voltage controller
with RL-load with neat circuit and
wave forms.
b) Discuss the
concept of synchronous tap changes. [12]
2. A 3-phase,
3-wire AC regulator supplies a star connected resistive load of R=10.0
ohm and line to
line input voltage is 230 V (rms), 50 Hz. The firing angle is 300.
Determine:
i) rms output
voltage.
ii) Input power
factor
iii) Expression for
instantaneous output voltage of phase R. [12]
3. A single phase
voltage controller feeds power to a resistive load of 3 Ω from
230V, 50 Hz source.
Calculate:
i) The maximum
values of average and rms thyristor currents for any firing
angle, ‘α ’.
ii) The minimum
circuit turn-off time for any firing angle,α .
iii) The ratio of 3rd
harmonic voltage to fundamental voltage for 3
α =π
iii) The angle, `α ’ at which the greatest forward or reverse voltage is applied
to either of the
thyristors and magnitude of these voltages. [12]
4. Explain the
operation of dual converter both circulating and non circulating
modes of operation.
Mention its applications, advantages and disadvantages.
[12]
5. What is pulse
width modulation control of converters and what are the
applications? A
single phase full converter is connected to RLE load. The source
voltage is 230 V,
50 Hz. The average load current of 10A is continuous over the
working range. For
R=0.4 Ω and L = 2mH, compute the firing angle
delay for
E=120 V. [12]
6. A three-phase,
half wave converter is operated from a 3-phase, Y-connected
440 V, 50 Hz supply
and the load resistance is R = 20 Ω .
If it is required to obtain
an average output
voltage of 50% of the maximum possible output voltage,
calculate:
a) Firing angle, α .
b) rms and average
output currents.
c) Rectification
efficiency.
d) Input power
factor. [12]
7. Discuss about
switched mode regulators. Explain the operation of buck and boost regulators. Mention the applications and
advantages of these regulators. [12]
8. Write about:
i) Single phase
bridge inverter.
ii) Harmonic reduction techniques.
APRIL
2011 NOVEBER NR-R09
ANALYSIS OF POWER ELECTRONIC CONVERTERS
1. a) Explain the operation of 1-φ voltage
controller with R-load with neat circuit and wave forms.
b) Explain two
stage sequence control of voltage controller for R-load. [12]
2. A 3-phase,
3-wire AC regulator supplies a star connected resistive load of R=10.0 ohm, and
line to line input voltage is 230 V (rms), 50 Hz. The firing angle is 300. Determine:
i) rms output
voltage.
ii) Input power
factor
iii) Expression for
instantaneous output voltage of phase R. [12]
3. A single phase
AC voltage regulator feeds a R-L load with the following parameters. Input
voltage = 230V (rms), frequency = 50 Hz, resistance R=4 ohms and inductance L =
10 mH. Calculate:
i) The control
range of firing angle,
ii) The maximum
value of rms load current,
iii) The maximum
power and power factor. [12]
4.a) What is a
Cyclo converter? Explain the principle and operation of single phase cyclo
converter with neat diagram and wave forms.
b) What are the
applications of cyclo converter? What are the effects of load inductance on the
performance of cyclo converters? [12]
5. A single phase
fully controlled thyristor bridge converter supplies on inductive load.
Assuming that the output current is virtually constant and is equal to Id,
determine the following performance measures, if the supply voltage is 230 V
and if the firing angle is maintained at 600.
a) Average output
voltage,
b) Input rms
current and input fundamental rms current,
c) Displacement
factor and power factor,
d) Supply harmonics
factor and voltage ripple factor. [12]
6. A 3-phase, fully
controlled bridge converter is connected to a three phase AC supply of 400 V,
50 Hz and operates at a firing angle of 450. The load current is maintained
constant at 10A and load voltage is 360 V. Compute
a) Source
inductance
b) Load inductance
c) Overlap angle
d) If the source
inductance is reduced to half, find the output voltage. [12]
7. Discuss about
switched mode regulators. Explain the operation of buck and boost regulators.
Mention the applications and advantages of these regulators. [12]
8. Explain the
voltage control of single phase inverters with the help of waveforms.
APRIL 2010 NOVEBER
ANALYSIS OF POWER ELECTRONIC CONVERTERS
1. A synchronous
tap changer is having primary voltage 240V(rms), 60Hz. The
secondary voltages
are V1=120V andV2 =120V. If the load resistance is R = 0Ω and the rms load
voltage is 180V. The delay angle is α = 49π/90 = 980. Determine the rms currents
of T1, T2, T3, T4 thyristors.
2. With necessary
waveforms explain the operation of a three phase star connected ac voltage controller for a firing angle of α =
300.
3. (a) Analyze a
three phase to three phase cycloconverter with midpoint configuration.
(b) What are the
advantages of a cycloconverter?
4. A single-phase
full converter with a highly inductive load so that the load current is continuous
and ripple free is connected to a 120V, 60Hz supply. The turn’s ratio of
the transformer is
unity.
(a) Express the
input current in a Fourier series; determine the HF of the input
current, DF and
input PF.
(b) If the delay
angle is α = π/3, calculate Vdc, Vrms, HF, DF, PF.
5. Explain the
operation of a Cuk regulator. Derive the expressions for critical values of inductances and capacitances.
6. Explain about
the phase displacement control and advanced harmonic injection
modulation of a
single phase inverter.
7. With necessary
waveforms explain the 1200 conduction of a three phase bridge
inverter.
8. (a) What are the
different ways of combining two 6-pulse bridge converters to
produce an
effective 12-pulse output?
(b) Explain the
various parameters on which the quality of an inverter is normally
evaluated.
APRIL 2010
APRIL
ANALYSIS OF POWER ELECTRONIC CONVERTERS
1. a) Explain the
operation of a single phase ac voltage controller with RL load by
drawing the
necessary waveforms.
b) Also explain the
operation when firing angle α is less than load phase angle
φ ( α<φ ).
2. With necessary
waveforms explain the operation of a three phase star connected
ac voltage
controller.
3. a) Explain the
operation of a single phase step down cycloconverter.
b) What are the
advantages, disadvantages and applications of a cycloconverter?
4. a) Explain the
operation of a single phase dual converter.
b) Explain the
techniques of extinction angle control and symmetrical angle control
for the improvement
of power factor of phase controlled converters.
5. a) What are the
different ways of combining two 6-pulse bridge converters to
produce an
effective 12-pulse output?
b) The load current
of a three phase full converter is continuous with a negligible
ripple content.
Express the input current in Fourier series and determine the HF of
input current, the
DF and the input pf .
6. a) Explain the
operation of a Buck regulator. Derive the expressions for the critical
values of
inductance and capacitance.
b) A Buck regulator
has an input voltage of Vs=12 V. The required average output
voltage is Va=5 V
at R=500Ω and the peak-to-peak output ripple voltage is 20mv.
The switching
frequency is 25 KHz. If the peak-to-peak ripple current of inductor
is limited to 0.8A.
Determine a) The
duty cycle K b) Fitter Inductance L
c) Filter
capacitance C d) Critical values of L and C.
7. Explain the
single PWM, multiple PWM, and sinusoidal PWM and modified
sinusoidal PWM techniques of a single phase inverter.
8. With necessary
waveforms explain the 1800 conduction of a three-phase bridge inverter.