Categories: Third Year First Semester (3-1)

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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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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]

*****

R13

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