Anna University Chennai 2005 B.E POWER ELECTRONICS - Question Paper
Saturday, 23 February 2013 11:55Web
Code: A-26
Time: three Hours Subject: POWER ELECTRONICS
Max. Marks: 100
NOTE: There are 11 ques. in all.
ques. one is compulsory and carries 16 marks. ans to Q. 1. must be written in the space given for it in the ans book supplied and nowhere else.
ans any 3 ques. every from Part I and Part II. every of these ques. carries 14 marks.
Any needed data not explicitly given, may be suitably presumed and said.
_____________________________________________________________________Q.1 select the accurate or best option in the following: (2x8)
a. Which of the subsequent devices has high input impedance and low conduction losses
(A) SCR.
(C) TRIAC. (B) IGBT.
(D) ) GTO.
b. A single phase full bridge converter can operate in
(A) Single Quadrant.
(C) 2 Quadrant.
(B) 3 Quadrant.
(D) 4 Quadrant.
c.
A single phase full bridge converter can operate in
(A)
(C)
(B)
(D)
d. McMurray full bridge inverter uses
(A) Auxiliary commutation.
(C) Complementary commutation.
(B) Natural commutation.
(D) Load commutation.
e. In a Pulse Width Modulation (PWM) chopper
(A) T is kept constant and TON is varied.
(B) ON is kept constant and T is varied.
(C) Both ON and T are varied.
(D) Both ON and T are kept constant.
f. A cycloconverter uses
(A) Natural commutation.
(B) Forced commutation.
(C) Both natural and forced commutation.
(D) Either natural or forced commutation.
g. The output of a voltage regulator varies ranging from 15 V and 14.7 V at no-load and full load. The voltage regulation is
(A) 0.2%.
(C) 2.4%. (B) 0.3%.
(D) 2.04%.
h. In a single phase full-wave ac voltage controller feeding RL load, the gate pulses are
(A) short duration pulses.
(B) long duration pulses.
(C) continuous pulses of duration (-).
(D) either short or long duration pulses.
_______________________________________________________________
PART I
ans any 3 ques.. every ques. carries 14 marks.
_______________________________________________________________
Q.2
Compare the salient features of SCR and IGBT. (4)
Explain the turn on and turn off mechanism of GTO and provide advantages and disadvantages of GTO over SCR.
(10)
Q.3
With neat diagram and waveforms discuss the principle of working of a fully controlled bridge converter with resistive load. (8)
A single phase semi converter is connected to a 120 V, 60 Hz supply. If the firing angle , obtain the
(i) avg. output voltage. (ii) RMS output voltage.
(6)
Q.4
Explain, with neat diagram and waveforms, the working principle of a 3 phase half wave converter with resistive load.
(8)
A 3 phase fully controlled bridge converter is fed from 400 V, 50 Hz supply. obtain the avg. output voltage for firing angles of
(i) 30° (ii) 45°.
(6)
Q.5
discuss the V-I characteristics of UJT and draw the circuit of a relaxation oscillator using it. (7)
What do you mean by commutation of SCR? discuss briefly the different commutation methods used for SCRs. (7)
2
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What is a dual converter? discuss the principle of working of a single phase dual converter with neat diagram and waveforms. (10)
Mention the advantages of circulating mode dual converter over non-circulating mode dual converter.
(4)
_______________________________________________________________
PART II
ans any 3 ques.. every ques. carries 14 marks.
_______________________________________________________________
Q.7
Draw the circuit diagram of a 3 phase bridge inverter with conduction 120° mode and resistive load. (4)
Explain the principle of working of the above circuit with gating trend and wave forms of output line voltages and phase voltages. (10)
Q.8
discuss the principle of operation of a single phase to single phase cycloconverter using bridge configuration.
(8)
The input to a single phase cycloconverter is 120V, 60 Hz. The load resistance is 5. The frequency of output voltage is 20 Hz. If the firing angle is , determine the rms output voltage and the rms load current
(6)
Q.9 Explain with neat diagrams, the principle of working of a step-down chopper with RL load. (7)
With a neat diagram, discuss the principle of working of Switch Mode Power Supply (SMPS). (7)
Q.10 Draw the circuit of a McMurray-Bedford inverter and discuss the principle of working. (8)
What are the different methods of single phase inverter output voltage control? discuss sinusoidal pulse width modulation scheme (6)
Q.11 Explain with neat diagrams the working principle of a single phase full wave ac voltage controller with RL load, (8)
A single phase ac voltage controller has an input voltage of 150 V and load resistance of eight ?. The firing angle of thyristors is 60°. obtain
(i) avg. output voltage. (ii) RMS output voltage. (6)
| Earning: Approval pending. |
