Download AKTU B-Tech 4th Sem 2014-15 Electro Mechanical Energy Conversion I Question Paper

Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 4th Semester (Fourth Semester) 2014-15 Electro Mechanical Energy Conversion I Question Paper

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(Following Paper ID and Roll No. to be ?lled in your Answer Book)
PAPER ID : 121405
Roll No.
B. Tech.
(SEM. IV) THEORY EXAMINATION, 2014-15
ELECTRO-MECHANICAL ENERGY CONVERSION - I
Time : 3 Hours] [Total Marks : 100
Note : Attempt all questions.
1 Attempt any two parts of the following : 10X2=20
(a) Derive an expression for electromagnetic torque
in singly excited lineal magnetic system.
(b) Write the energy bala ce equation for motor and
generator. 'Why magnetic ?eld is used as a
coupling medium in electromechanical conversion
device ?
(c) A doubly excited system has a stator inductance
of 0.6 H, rotor selfinductance=0.3 H and mutual
inductance=0.4 H. The value of the rotor and
the stator current under steady state are 10A and
8A. Calculate the total stored magnetic ?eld
energy.
121405] 1 [ Contd...

2 Attempt any two parts of the following .
(a)
.(b)
(C)
3 Attempt any two parts of the following :
(a)
(b)
1214051
What is reactance voltage ? How is it produced
in a DC machine ? Also explain its effects on
the performance of DC machine.
A 6-pole DC shunt generator supplies ?Jll-load
current at a terminal voltage of 250 V. The
armature and ?eld resistances are 0.042 (2 and
100 9 respectively. It runs at a speed of 1000
rpm and has 700 lap connected conductors. The
voltage across armature resistance is 7.2 V. Find
the follo'wing :
(1) load current
('11) emf generated
(iii) the ?ux/pole.
Neglect brush contact drop.
Compare and contrast between the external
characteristics of all types of DC generators.
A 250 V, 30 kW, 1200 rpm, DC shunt motor
has a full load ef?ciency of 88%. The armature
resistance is 0.29 O and total brush drop is 2V.
The value of the ?eld current is 2A. Determine :
(1) Full load line current
(ii) Full load shaft torque and
(iii) Total resistance in the motor starter to limit
the staiting current to 1.5 times the ?ll] load
current.
What is the drawback of a three-point starter ?
How are these drawbacks eliminated in a four
point starter ?
2 [ Contd...
10 X2=20
10><2=20
(C)
4 Attempt any two parts of the following :
(a)
(b)
'(C)
5 Attempt any two parts of the following :
(8)
121405]
A 260 V, DC shunt motor draws no load cment
of 4A. The armature and ?eld resistances are
0.5 Q and 250 (2 respectively. Find the ef?ciency
of the machine as a generator and that as a motor
when the load current is 25 A.
Describe the back-to-back test for determining
the regulation and ef?ciency of a pair of similar
transformer. What are the limitations of this
test ?
What is an auto transformer ? Discuss the
advantages, disadvantages and applications of
auto transformers. Compare the conductor savings
of auto ttansfonner with a two winding transformer.
In a scott connection, the loads on the two-phase
side are 400 kW and 500 kW, both at 200 V
and 08 p.f. lagging. The three phase line voltage
is 2200 V. The 400 kW load is on the leading
phase on the two-phase side. Neglecting
transformer losses, calculate the value of line
currents on the three-phase side.
Find the approximate equivalent circuit of a single-
phase 100/1000V transfomter having the following
test results:
OC Test: 100 V, 1.2 A, 150 W
SC Test : 35 V, 15 A, 750 W
C
3 [ Contd...
10X2=20
10><2=20

(b) Discuss relative advantages and disadvantages of
employed three 1?4) transformers for use in 3?Cb
operation over employing a single unit 3 ? <1) transformer.
((2) Write short notes on any two of the following :
(i) All-day ef?ciency of a distribution transformer.
(ii) Armature reaction in DC machines.
(iii) Hopkinson's Test.
121405] 4 [2275]