SKR Engineering College 2007 B.E Electrical and Electronics Engineering EE 1251 – ELECTRICAL MACHINES - II - Question Paper

S K R ENGINEERING COLLEGE
POONAMALLEE, CHENNAI-602103

Fourth Semester
ELECTRICAL & ELECTRONICS ENGINEERING
EE 1251 – ELECTRICAL MACHINES - II

MODEL exam
Date: 25.04.2007
Time: three Hours Maximum: 100
ans ALL ques.
PART A [10X2=20]
1. List the kinds of rotors of synchronous generator and compare the same?
2. What are the conditions for parallel operation of alternator?
3. What is hunting in Synchronous Motor? How it can be minimized?
4. Enlist the advantages & Disadvantages of Synchronous Motor?
5. A 3-Phase, four Pole, 50 Hz Induction Motor is running at 1440 rpm. Determine the slip speed (Ns –N) and Slip?
6. What is an Induction Generator?
7. Give the functions performed by induction motor starter?
8. What is the effect of change in Input Voltage on starting torque of Induction Motor?
9. State Double Revolving Field Theory?
10. List out 4 Applications of Shaded Pole Induction Motor?
PART B [5 X16=80]
11. A. (i) discuss the Constructional Details of a 3 phase Alternator which
is used for slow speed operation? [8]
(ii) A 3-Phase, six Pole, Star connected Alternator revolves at 1400 rpm.
The stator has 90 slots and eight conductors per slot. The Flux per pole
Is 0.05 wb.(Sinusoid ally Distributed) compute the voltage
Generated by machine if the winding factor is 0.96. [8]
OR
B. (i) explain the Synchronous impedance method of calculating
Regulation of an alternator & mention its advantages,
Disadvantages? [8]
(ii) discuss the 2 REACTION THEORY of synchronous machine
with neat diagram and how can Xd, Xq be determined by slip test?
[8]
12. A. explain the subsequent
(i) V & Inverted V Curves
(ii) Starting Methods of Synchronous Machine [16]
OR
B. Draw & discuss the phasor diagram of current locus for
i. Constant Excitation
(ii) Constant Power Developed in synchronous motor when Normal,
Under, Over, Critical Excitation is given. [16]
13. A. (i) define the principle of operation of Synchronous Induction Motor?
[8]
(ii) calculate the value of Maximum Torque in N-m for a 3-Phase, 440V,
Star connected 50 Hz, four Pole induction motor for which X1 = 5.2
ohm, R2’ = 1.2 ohm, X2’ = 4.5 ohm. Also determine the slip
corresponding to it. [8]
OR
B.(i) Draw the Slip Torque Characteristics of 3-Phase Induction Motor? [8]
(ii) With neat diagram, discuss the construction, working, characteristics,
Applications of Double Cage Rotor Induction Motor? [8]
14. A. Is a three-phase induction motor is self-starting? How are they started?
describe Starter; explain the theory of any three starters? Mention its
Advantages & Disadvantages? [16]
OR
B. elaborate the ways by which speed of the induction motor can be
controlled? discuss the slip power recovery scheme? [16]
15.A. discuss the operation of a
(i) Single phase Induction Motor using Double Revolving Field Theory [8]
(ii) Develop the equivalent circuit of a 1-Phase induction motor. [Ignoring Cu Loss] [8]
OR
B. With neat diagrams, discuss in detail on
(i) Hysteresis Motor [8]
(ii) Stepper Motor [8]









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