ELECTRIC MACHINES IMPORTANT QUESTIONS

IMPORTANT QUESTION MAY/JUNE 2014

ELECTRICAL MACHINES-1

PART – B QUESTIONS :

Unit- 1

1. Explain AC operation of magnetic circuits and derive the energy stored in magnetic

field .(8)*

2. Explain the core losses that occurs in magnetic circuits in detail. (8*)

3. Explain in detail how the emf is induced . (16)*

4. Compare magnetic circuits and electric circuits (8)*

5. Explain (a)leakage flux( b)stacking factor (c) air gap. (8)

Unit -2

1. Explain parallel operation of single phase transformer. And derive the emf equation of

transformers. (16)*

2. Explain the working and construction of auto transformer in detail.(8)

3. Draw and explain the equivalent circuits of transformer (16)

4. Explain all the three phase transformer connections . (16)*

5. Explain a)transformer on ON load b)transformers on NO load conditions. (Each 8 ) 

Unit -3

1. Explain in detail singly excited magnetic system (be in knowledge with full derivation

in safer side ) .(16)*

2. Explain in detail multiply (or) doubly excited magnetic system .(16)*

3. Draw and explain the energy flow diagram for a motor and generator. what is field

energy and co-energy ? (10)

Unit -4

1. Explain generated voltage in AC and DC machines. (16)*

2. Explain MMF in single coil winding .(8)*

3. Explain MMF in a multiple coil distributed winding (16)*

4. Explain and derive the torque in round rotor machines in terms of flux and flux

density.(16)

Unit -5

1. Explain the methods of excitation in DC generators (16)*

2. Explain characteristics of DC generator.(16)*

3. Explain in detail the armature reaction in the DC machines. (16)*

4. Explain the process of commutation and the methods to improve the commutations

.(16)*

5. Explain the three point starter in detail with diagram .(8)

6. Explain the methods speed control of DC shunt motor. (8)*

7. Explain the methods speed control of DC series motor.(8)

8. Explain any 2 methods of testing of DC machines .(8)* 

Tips:

Problems are expected from 1^st and 5^th unit.......

Be in knowledge with all theory question mentioned above as you can be confident in attending the exam.

In related to 3th unit. Surely theory question can be expected from mentioned

above question ... if not problem can be asked....

· -> important.. in 5th

 unit.... many theory questions are there...we have mentioned some repeated questions..

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NOTE :MENTION (*) IS MORE IMPORTANT OF UNIVERSITY EXAMINATION MAY BE OR MAY NOT BE ASKED SO PREPARE WELL