# PTU B.Tech Electrical Engineering 6th Semester May 2019 71147 ELECTRIC POWER UTILIZATION Question Papers

PTU Punjab Technical University B-Tech May 2019 Question Papers 6th Semester Electrical and Electronics Engineering (EEE)-EE-Electrical Engineering

Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(EE/Electrical & Electronics)
B.Tech.(Electronics & Electrical) (2011 Onwards)
B.Tech.(Electronics Engg.)/(Electrical Engg. & Industrial Control)
(2012 Onwards) (Sem.?6)
ELECTRIC POWER UTILIZATION
Subject Code : BTEE-601
M.Code : 71147
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3.
SECTION-C contains T HREE questions carrying T EN marks each and students
have to attempt any T WO questions.

SECTION-A
1.
Write briefly :

a. Compare a group drive and an individual drive.

b. Classify load torques depending on the speed.

c. State the requirements of an ideal traction system.

d. Give the general features of motors in traction service.

e. List the properties of good heating elements.

f. Give the demerits of eddy current heating.

g. Define the term Annealing.

h. State the laws of illumination.

i. Explain the Stroboscopic effect.

j. Give the purpose of electroplating.
1 | M - 7 1 1 4 7

( S 2 ) - 2 2 7 4

SECTION-B
2.
Derive an expression for moment of inertia of flywheel for intermittent loading.
3.
Derive the relation between the principle quantities of quadrilateral speed time curve.
4.
Discuss the various aspects of residential lighting, street lighting & flood lighting.
5.
Describe butt welding and its various applications.
6.
Define Air Conditioning. How is air purified from micro-organism, gaseous contaminates
and odours?

SECTION-C
7.
a. What are the various methods of speed control of series motors and their scope of
speed range?

b. A 20 kW induction motor has a final steady temperature of 40?C when running at its
rated output. Calculate its half hour rating for the same temperature rise if the copper
losses at the rated output are 1.2 times its constant losses. The heating time constant is
90 minutes. Derive the expression used.
8.
a. Explain the energy losses in separately excited motor during braking and compare
dynamic braking with plugging.

b. A single phase full wave converter is used to control the speed of a 10kW, 230V,
1200 rpm, separately excited dc motor. The supply voltage of the converter is 240V,
50Hz. The motor parameters are Ra = 0.5, La = 5mH, voltage constant
(k) = 0.175 V/rpm.

(i) If the motor runs at 1000 rpm and takes an armature current of 30A (assumed to
be ripple free), determine the firing angle a.

(ii) If the polarity of the field excitation is reversed under motoring condition,
determine the firing angle to keep motor running at 1000 rpm and taking
armature current of 30A.
9.
a. Explain the working of core type induction furnace with a neat sketch.

b. A 7KW, 440 volts, 3-phase resistance oven is to have a 3-star connected nichrome
strip of 0.4 mm thick heating element. If the wire temperature is to be 1500?C and
that of the charge 1000?C, estimate the suitable width of the strip. Resistively of
nichrome alloy is 1.016 ? 10?6. Assume the radiating efficiency and emissivity of the
element as 0.6 and 0.91 respectively.

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