JNTU Kakinada B-Tech 3-1 RT31024 I ELECTRICAL MACHINES – III R13 April 2018 Question Paper

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Code No: RT31024
III B. Tech I Semester Supplementary Examinations, May -2018
ELECTRICAL MACHINES ? III (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Note: 1. Question Paper consists of two parts (Part-A and Part-B) 2. Answering the question in Part-A is compulsory
3. Answer any THREE Questions from Part-B
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PART ?A
1 a) Explain the different methods of starting of a single phase induction motor? [3M]
b) Explain in detail about the stator winding in Synchronous generator. [3M]
c) Explain the effect of armature resistance and leakage reactance on the synchronous
generator.
[4M]
d) Explain the role of damper winding in synchronous generator. [4M]
e) Explain the principle of operation of Synchronous motor. [4M]
f) What is a synchronous condenser? What are its applications? [4M]
PART -B
2 a) Explain the principle of operation of a capacitor ? start capacitor ? run induction
motor with suitable diagrams.
[8M]
b) Discuss the procedure to determine the parameters of equivalent circuit of a Single
? phase induction motor.
[8M]
3 a) List and explain the salient features of cylindrical ? rotor ? type synchronous
machine
[8M]
b) A delta connected three phase 15 KV, 600 rpm, 50 Hz, 4 pole generator has 4 slots
per pole per phase. The coil span is 10 slots and there are 20 turns per coil.
Determine the flux per pole if the generator has double layer winding.
[8M]
4 a) Explain the reasons for providing armature winding on the stator and low power
field winding on the rotor.
[8M]
b) Derive the emf equation of a synchronous generator.
[8M]
5 a) Explain the conditions that must be fulfilled for parallel operation of two
synchronous generators.
[8M]
b) A 12 KVA,440 V, 50 Hz, star connected synchronous generator supplies rated load
at 0.8 power factor lagging. The armature resistance and synchronous reactance are
0.3 ? and 8 ? respectively. Determine the torque angle and the voltage regulation.
[8M]
6 a) Explain the different methods of starting of synchronous motors. [8M]
b) A 2500 V, three phase star ? connected synchronous motor has a resistance of
0.35? per phase and synchronous reactance of 2.2 ? per phase. The motor is
operating at 0.75 power factor leading with a line current of 250 A. determine the
excitation voltage per phase.
[8M]
7
Write short notes on the following:
i)causes of Hunting and its suppression
ii) Mathematical analysis of power developed in Synchronous motor
[16M]
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R13
SET – 1