EEPW 2251 MCBS Electrical and Electronics Engineering Questions shathan10- ELCTRONICS AND COMMUNICATION ENGINEERING ………………………..

EEPW 2251 MCBS Electrical and Electronics Engineering Questions shathan10- ELCTRONICS AND COMMUNICATION ENGINEERING

……………………………….. HIGHER COLLEGE OF TECHNOLOGY
DEPARTMENT OF ENGINEERING
SECTION:
EEE ?
CAE
MIE
Final Assignment
Semester: 2
A. Y: 2019 / 2020
Date of Assignment posting: 1st May 2020
Date of Uploading:
Time: 12:00 PM
3rd May 2020 Time: 12:00 PM
Student Name
Student ID
Specialization
Electrical Engineering
Level
DSY
Course Name / Course Code
Electrical Power Technology/EEPW2251
Section No.
1,2,3
Moderator’s Approval: ?
PC’s Approval: ?
48 hours
Question No.
Max. Marks
PART- 1
10
PART- 2
10
PART- 3
20
Obtained
Marks
Question No.
Sub-Total
Marks
Grand Total
Marks
Max. Marks
Sub-Total Marks
____ / 40
Course Lecturer: Ms. Sowmya Saraswthi P
Second Marker:
Assignment instructions from Course Lecturer:
a) Type the theory and problems answers in word file
b) Type the theory answers in your own words.
c) Diagrams alone – draw neatly, scan and add in the word file.
Student’s Declaration: (to be filled by student)
Student Name: __________________
ID: _________
Signature: _________
(Digital Signature)
Page 2 of 5
Obtained
Marks
PART – 1 (10 marks)
SHORT ANSWER QUESTIONS
Q 1.
The efficiency of transformer is more, because ______________________.
[1]
a). It is a static device
b). It has two windings
c). It has only one core
d). It has more losses
Q 2.
The eddy current loss & hysteresis losses of a transformer at 50Hz are 50W & 40W
[1]
respectively. The core loss of the same transformer at 25Hz is ____
a). zero
b). 90W
c). 45W
d). 32.5W
Q 3.
The speed of dc shunt motor is ___________________________.
[1]
a). Inversely proportional to field current.
b). Directly proportional to field current
c). Inversely proportional to field circuit resistance.
d). Directly proportional to armature resistance.
Q 4.
Three identical capacitors with 10ohms capacitive reactance are connected in star
[1]
takes 1A current from supply. The active power taken by the load is __________.
a). Equal to zero
b). Equal to real power.
c). 20W
d). 20VAR
Q 5.
Which of the following statement is true for a dc series motor?
a). Back e.m.f is greater than terminal voltage.
b). Voltage drop in the armature winding is same as field winding voltage drop.
c). Field winding is connected in parallel with armature.
d). None of the above
Page 3 of 5
[1]
Fill in the blanks
Q 6.
(5 x 1 = 5marks)
Three loads, each of resistance 30? are connected in star to a 415V, 3-phase
[1]
supply. The power factor of load is ________________.
Q 7.
A 5kVA ideal step- up transformer with a turn’s ratio of 2:7 is fed from a 240V
[1]
supply. Its output current on no load is ______________.
Q 8.
In _____________ wound generators, the generated emf is independent of number
[1]
of poles?
Q 9.
The angle between voltages in R phase and B phase of a supply with RYB phase
[1]
sequence is ___________.
Q 10.
The angle between primary voltage and core magnetic flux in a transformer under
[1]
noload condition is _______.
PART – B (10marks)
NOTE: USE DIAGRAM, GRAPHS IF ANY FOR ANY EXPLANATION and/or DERIVATION/S FOR
THE ANSWERS BELOW.
Q 11. Draw the phasor diagram of a step-up transformer connected to an incandescent lamp.
Q 12.
Why delta connected load dissipates more heat than when they are connected in star
[3]
[2]
across same supply?
Q 13.
While conducting OC test on a single phase transformer, instead of connecting the ac [3]
source to the primary of transformer, you are connecting the primary to a rectifier. What
will happen to the transformer?
Q 14.
Explain how the power factor of a 3-phase delta connected load can be measured? Draw
the circuit diagram.
Page 4 of 5
[2]
PART – C (20 marks)
Numerical Questions
Q 15. A DC shunt generator is driven by a diesel motor. The shaft torque of the diesel motor is
[3]
35Nm, when the current through the armature of the generator is 20A. If the shunt field
regulator is adjusted so that the flux is increased by 15%, the torque decreases to 25Nm.
Determine the armature current at this new value of torque.
Q 16.
A DC shunt generator generates 400V when running at 1800rpm.Determine how much
[2]
percent the flux has to increase per pole, to generate 500V when running at 20rps.
Q 17. A three phase star connected alternator delivers a line current of 65A to a balanced
delta connected load at a line voltage of 380V.calculate
(i)
The phase voltage of alternator,
(ii)
The alternator phase current
(iii)
The load phase current
Q 18. A shunt motor having an armature circuit resistance of 1? and a field resistance of 125?,
[2]
[2]
connected to of 250V supply. Determine the efficiency of the motor when it takes 50A
from the supply, assuming constant losses amount to 500W.
Q 19. A delta-connected load consists of three identical coils each of resistance 3 ? and
inductive reactance of 4 ?.this load is connected to a star connected alternator through
wires. The resistance of each wire is 0.025 ?.The power dissipated by each phase of the
load is 19.2kW. How much power will be dissipated in the wires? Also find the
alternator voltage.
Q 20. A 200kVA, 4000V/2000V, 50Hz single-phase transformer has 100 secondary turns. The
transformer primary winding has resistance and reactance of 1 ? & 0.5 ? respectively and
the transformer secondary windings has resistance and reactance of 0.25 ? & 0.1225 ?
respectively. Determine
(a) the copper losses in primary and secondary windings at full load,
(b) The maximum value of flux density in the core if the area of cross section is 300 cm2.
(c) The efficiency of the transformer at full load,( assume UPF), if the total core losses is
100W.
__________________ End of the Assignment __________________
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