Download GTU BE/B.Tech 2017 Winter 5th Sem Old 150802 Electrical Machines Question Paper

Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2017 Winter 5th Sem Old 150802 Electrical Machines Previous Question Paper

1
Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY
BE SEMESTER?V (OLD) ? EXAMINATION ? WINTER 2017

Subject Code: 150802 Date: 03-11-2017
Subject Name: Electrical Machines
Time: 10:30 am to 01:00 pm Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1 (a) Explain Swinburne?s test in D.C. Machine. 07
(b) Explain demagnetizing and cross magnetizing effects of armature reaction
giving neat diagrams.
07

Q.2 (a) Draw the circle diagram of a 20 hp, 400 V, 50 Hz, 3-? star-connected induction
motor from the following test data(line values)
No Load test =400 V 9 A p.f.=0.2
SC test =200 V 50 A p.f.=0.4
The stator and rotor copper losses are divided equally in the SC test. From the
circle diagram find (1) line current and power factor at full load (2) maximum
power output.
07
(b) Draw the developed view diagram of lap winding for 4 poles and 12 slots
armature with two coil sides per slot.
07
OR
(b) Explain the harmonic phenomena in (i)delta connected (ii)star connected
winding of three phase transformers
07

Q.3 (a) Explain no load test and blocked rotor test on three phase induction motor. 07
(b) Explain the Scott connection with vector diagram for transformer. 07
OR
Q.3 (a) Give detail of the cogging and crawling phenomena for three phase induction
motor.
07
(b) Show schematically how a 3-phase transformer can be phased- in with another
3-phase transformer
07

Q.4 (a) Describe briefly the methods of controlling speed of an Induction motor. 07
(b) Explain equivalent circuit of three phase induction motor. 07
OR
Q.4 (a) Explain principle of stepper motor with its construction. 07
(b) Explain effects of varying excitation on armature current and power factor in a
synchronous motor. Draw ?v? curves
07

Q.5 (a) Using Double Revolving Field Theory, describe in detail why single phase
induction motor is not self starting.
07
(b) Explain the construction and operation of permanent magnet brush less DC
motor.
07
OR
Q.5 (a) Explain capacitor start and capacitor run single phase induction motor. 07
(b) Write short note on Universal motor. 07

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