B explain unipolar switching scheme operation for a

b) Explain unipolar switching scheme operation for a PWR inverter?
R13 SET - 3

|''|'''||''||'''||||
Code No: RT31025
III B. Tech I Semester Regular/Supplementary Examinations, October- 2016
POWER ELECTRONICS
(Electrical and Electronics Engineering)
Time: 3 hours Max. Marks: 70
Note: 1. Question Paper consists of two parts ( Part-A and Part-B)
2. Answering the question in Part-A is compulsory
3. Answer any THREE Questions from Part-B
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PART –A
1 a) Describe the significance of di/dt and dv/dt in SCRs. [3M]
b) Explain the principle of line commutation. [4M]
c) Explain the effect of battery load on the performance of single phase fully controlled
bridge converter.
[3M]
d) What are the advantages of 6-pulse converter over 2-pulse converter? [4M]
e) What are the control strategies for the regulation of output voltage in ac voltage
controller?
[3M]
f) Explain the operation of single-phase inverter. [4M]
PART -B
2 a) For a single phase half wave rectifier feeding a resistive load R, find the values of
rectifier efficiency, form factor, voltage ripple factor, transformer utilization factor
and crest factor when
0
0 = α
[10M]
b) Explain briefly different turn on methods used for SCR. [6M]
3 a) Define the term power factor. Derive its expression for single phase voltage
controller feeding a resistive load circuit.
[7M]
b) A resistive load of 10 Ω is connected through a half-wave SCR circuits to 220v,
50Hz, single- phase source. Calculate the power delivered to load for a firing angle of
60
0
.Find also the value of input power factor.
[9M]
4 A Single phase full converter delivers a constant load current I
o
. Express its source
current in Fourier series and derive expressions for the following performance
parameters. ( i ) Displacement factor ( ii ) Power factor ( iii ) THD
( iv ) Current distortion factor
[16M]
5 a) Explain the operation of a three phase dual converter in the non circulating current
mode with the help of relevant waveforms. Derive the expression for the average
output voltage.
[10M]
b) A three phase fully controlled bridge converter is fed from a 3-phase 400 V, 50Hz
mains. For firing angle of 60
0
, output current is 25 A and output voltage is 250 V.
Calculate the load resistance, source inductance and angle of overlap.
[6M]
.
1 of 2
R13
SET - 4

Code No: RT31025
6 a) Discuss the working of a single phase bridge type cyclo converter with RL load for
continuous conduction operation with relevant output waveforms and circuit diagram
for f
0
= (1/4) f
s
.
b) Explain the principle of operation of a Back- Boost converter. [8M]
7 a) Explain the working of a single-phase half bridge inverter. Discuss how the output
power in single-phase full bridge inverter becomes four times the power handled by a
single phase half-bridge inverter.
[8M]
b) Describe briefly and compare the various methods employed for the control of output
voltage of inverters.
R13
SET - 4