27-08-2012, 03:06 PM
ELECTRICAL MACHINE-I QUESTION PAPER
ELECTRICAL MACHINE.doc (Size: 26 KB / Downloads: 44)
Answer ALL Questions
Part-A
1. State lenz’s law
2. Distinguish statically and dynamically induced emf
3. Why transformer rating expressed in kva
4. Write down the condition for maximum efficiency of transformer
5. Define field energy and coenergy
6. Write down the example for single excited system
7. Define rotating magnetic field
8. What does speed voltage means
9. Define armature reaction and what are the effect
10. Write down the significance of back emf
Answer either a or b from each Questions
Part-B
11.a )a flux of 0.25 mwb is produced when a current of 2.5a passes through a coil of 1000 turns. calculate
i) self inductance
ii) emf induced in the coil if the current of 2.5 a is reduced to zero in 1 milliseconds
iiii) if second coil of 100 turns is placed near to the first on the same ring, calculate the mutual inductance between the coils.
(or)
b)i) explain the ac operation of magnetic circuit
ii)explain about the core loss
12)a) explain the equivalent circuit of transformer
(or)
b.i)derive the savings of copper in autotransformer
ii)explain any four type of 3 phase transformer connection
13)a)describe i-λ relationship derive the co-energy density by assuming i-λ relationship of the magnetic circuit is linear
(or)
bi) draw the block diagram for electromechanical energy conversion
ii)derive torque developed in multiple excited system