Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 3rd Semester (Third Semester) 2015-2016 INEE 301 Electro Mechanical Energy Conversion Question Paper
NEE?301
(Following Paper ID and Roll No. to be ?lled in your
Answer Book)
Roll No.
B.Tech.
(SEM. III) THEORY EXAMINATION, 2015-16
ELECTRO-MECHANICAL ENERGY CONVERSION-I
[Time:3 hours]
Note : Attempt all 3 Section.
SECTION-A
l. Attempt all parts of this section.
[Total Marks:100]
(2x10220)
(a) Why is the wave winding useful for high voltage
low current DC machines?
(b) How the back EMF does make the DC machine
self-regulatory??
(c) How the direction of rotation of the DC shunt
motor can be changed?
(d) Based on the principle of conservation of energy,
write an energy balance equation of the motor.
3100 (1)
P.T.O.
(6)
(f)
(g)
(h)
(ix
0)
State the phenomenon useful for the
electromechanical energy conversion in rotating
machines?
Give two applications of the DC shuntmotor and
DC compound generator.
How are the transformer losses affected by the
power factor of the connected load?
An autotrans-former has primary voltage VI and
secondary voltage V2, where V I>V2. Calculate the
fraction of power transferred inductively.
If Pi and Po represents iron loss and full load ohmic
loss, then ?nd the fractional load at which the
maximun?l power shall be transferred.
A 1000 KVA, 50kV/40kV single phase auto
transformer is: fully loaded. F indthe current in the
common section of the winding.
SECTION?B
Attempt any five questions from the following. (10X 5=50)
2.
8100
(0
Show that the torque in a doubly excited magnetic
system is equal to the rate of increase of the ?eld
energy with respect to the displacement at constant
currents.
(2) NEE-301
8190
(ii)
(i)
(ii)
Show that in a linear magnetic system the energy
and co-energy are represented by the same
expression.
Explain the commutator action in DC machines.
Also describe the ways for achieving good
commutation.
A 4?pole d.e. shunt generator with wave connected
armature has ?eld and armature resistance of
909 and 0.15 9. It supplies power to 25 lamps
rated at 100V, 60W each, calculate the armature
current and emf generated'neglecting brush drop.
Discuss the internal and external characteristics ofthe
DC shunt generator. Also explain why the load
characteristics of DC shunt generator have drooping
more?than that ofscparately excitedgenerator.
Compare the speed torque characteristics of DC shunt,
series and compound motor. Which machine is most
suitable for'traetion purpose?
What are the advantages of the ?eld flux control over
armature circuit resistance control method employed-?for
the-speed control of DC motors?
(3) P.?T.O.
6. . Showthat the VA rating of the auto transformer is more
than the corresponding two winding transformer.
Show that in case of an auto transformer
inductively transferred power _ high vollage ?low voltage
total power high voltage
7. A 2300/220 V 500 kVA, 50 Hz distribution transfomier
has the core losses of 1600 W at rated voltage and
copper loss 7.5 kW at full load. During the day, it is
loaded as follows:
% Load 0% 20% 50% 80% 100% 125%
Power Factor 0.7 lag 0.8 lag 0.9 lag 1 0.85 lag
Hours 2 4 4 S 7 2
8. Explain the back to test for testing of the single phase
transformers. Also explain how the reading of the
wattmeter recording the core losses remain unaffected
when the low voltage is injected in the secondary series
circuit.
9. An electrical machine has cylindrical stator and salient
pole rotor. Justify the correctness of the following
statement :
(i) Reluctance torque is producted when exciting
winding is on rotor.
8100 (4) NEE?301
Attempt any two questions of the following.
10.
11.
8100
( ii) When stator and rotor both carry exciting winding,
electromagnetic as well as reluctance torque are
produced.
SECTION-C
(15x2=30)
Explain the conditions to be satis?ed for the successful
parallel operation of the single phase transformers.
Two single phase transformers rated 1000 kVA and 500
kVA respectively are connected in parallel on both HV
and LV sides. They have equal voltage rating of l 1 kW
400 V and their per unit impedances are (0.02+j
0.07)Q and (0.0025+j 0.0875) Q respectively. What
is the largest value of the unity power factor load that
can be delivered by the parallel combination at the rated
voltage?
Explain the Hopkinson test for determining the
ef?ciency of the DC shunt machine.
A 50kW, 250 V compound motor takes a current of 9 A
running at no load at rated voltage and rated speed. The
shunt field current is 5A. The resistance of the windings
is as armature winding 0.1 .Q , series [ield 0.07 .0 ,
interpolar windings 0.03 .0. The brush drop is 2V.
Determine the motor output and the ef?ciency of the
motor when the intake is 155 A.
? (5) P.T.O.
12. Write short notes on:
(i) Ma netization characteristics for DC shunt
g
generator.
(ii) Three phase to two phase connection.
(iii) In-Rush Current in transformers.
..__.X.._
8190 {(6) NEE??301
This post was last modified on 29 January 2020