SRM University 2008 B.Tech Electrical and Electronics Engineering ELECTRICAL MACHINES-II - Question Paper

B.Tech DEGREE EXAMINATION,DECEMBER 2008
2nd Semester
PEE202-ELECTRICAL MACHINES-II
Time:3 Hours Max.marks:100
ans ALL ques.
PART-A(10*2=20 Marks)


1.Write the condition for T max under running condition .

2.Define Cogging of induction motor .

3.Draw the power stages of induction motor.

4.Name a few methods of starting squirrel cage induction motor.

5.Why single phase induction motor is not self –starting?

6.Define voltage regulation of alternator.

7.What are the conditions for parallel operation in alternators?

8.Define :Synchronous condensers.

9.What are the characteristic features of synchronous motor?

10.What are the Damper windings and why it is used?

PART-B(5*16 = 80Marks)
11.a.i.Draw and discuss the torque-slip characteristic of induction motor for various values of rotor
Resistance.

ii.A 4-pole, three phase induction motor operates from a supply whose frequency is 50Hz.calculate
(i)Synchronous speed(Ns)
(ii)Speed at which the maximum torque occurs.
(OR)
b.i. A 100 Kw ,3300V,50Hz 3-phase,star connected induction motor has a synchronous speed of 500
rpm .The full load slip is 1.8% and full load poweer factor is 0.85.stator copper loss =3500w,
rotational loss =1200w.calculate.
(i)Rotor copper loss.
(ii)Line current.
(iii)Full load efficiency.

12.a.Explain with neat diagram different methods of starting of 3-phase squirrel cage induction motor.
(OR)
b.Explain with neat diagram the construction and working principle of synchronous induction motor.

13.a.Explain with relevant sketches the double field revolving theorey of single phase induction motor.
(OR)
b.Explain the construction and working of reluctance motor and hysteresis motor.

14.a.A 100KVA ,3000V,50Hz,3-phase ,star connected alternator has effective armature resistance of
0.2?.the field current of 40A produces a short circuit current of 200A and an open circuit emf of
1040V .Calculate the full load voltage regulation at 0.8 power factor lagging and leading using emf
Method.
(OR)
b.What is meant by synchronization?what are the conditions for synchronization and discuss with a
neat diagram synchronization of 3 phase alternators.

15.a.Explain the construction and working principles of synchronous motor.
(OR)
b.Draw and discuss V and inverted-w V curves of synchronous motor.


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Earning:   Approval pending.