PTU Punjab Technical University B-Tech May 2019 Question Papers 4th Semester Electrical and Electronics Engineering (EEE)-EE-Electrical Engineering
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(Electrical & Electronics) (2013 Onwards)/
B.Tech.(Electronics & Electrical) (2013 Batch)
(Sem.?4)
ELECTRICAL MACHINERY-II
Subject Code : BTEEE-401
M.Code : 72385
Time : 3 Hrs. Max. Marks : 60
INSTRUCTIONS 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.
Answer briefly :
a. Why does a 3-phase induction motor always run at a speed less than the synchronous
speed?
b. How can the direction of rotation of the 3-phase induction motor be reversed.
c. Discuss the working principle of hysteresis motor.
d. What is meant by armature reaction of a synchronous machine?
e. Why is the voltage regulation of an alternator negative for leading power factor
loads?
f. Why are synchronous motors not self-starting?
g. Name any two types of starting method for a synchronous motor.
h. What are the similarities between induction motor and transformer?
i. What are V and inverted V curves in synchronous motor and their significance?
j. What is the need of starter for induction motor?
SECTION-B
2.
What is meant by slip in an 3-phase induction motor? Derive an expression for the
frequency of rotor currents in it.
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3.
Explain the effect of variation of excitation and mechanical input on the parallel
operation of alternators with necessary phasor diagram.
4.
What is synchronous condenser? What are the advantages of installing a synchronous
condenser in an electrical system?
5.
What is the principle of operation of a linear induction motor?
6.
What is hunting and discuss briefly various causes for hunting.
SECTION-C
7.
Discuss the procedure for determining the parameters of equivalent circuit of a single
phase induction motor.
8.
A 5 kW, three-phase Y-connected, 50 Hz, 440 V, cylindrical rotor synchronous motor
operates at rated condition with 0.8 pf leading. The motor efficiency excluding field and
stator losses is 95% and Xs = 2.5. Calculate :
a) Mechanical power developed
b) Back emf
c) Armature Current
d) Power angle
e) Maximum or Pull out torque of the motor.
9.
A 1.1 MVA, 2.2 kV, 3-phase, star-connected alternator gave the following test results
during OC and SC tests :
Field Current (A)
10
20
30
40
50
Open circuit voltage
0.88
1.65
2.20
2.585
2.86
(kV)
Short circuit current (A)
200
400
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The effective resistance of the phase winding is 0.22 /phase. Estimate the full-load
voltage regulation at 0.8 p.f. lagging by :
(a) Potier method
(b) Ampere-turn method.
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
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This post was last modified on 04 November 2019