JNTU III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008

JNTU III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008


(Electrical & Electronic Engineering)


1. Discuss the applications of solid insulating materials in high voltage power transformers.


2. Show graphically the relation between the breakdown field strength of a gas and

the gas pressure for uniform field with a constant electrode separation. Give the physical explanation of the curve.


3. Explain properties and applications of Glass and Ceramic insulating material used

in high voltage engineering. Compare their merits and demerits.


4. (a) Explain and compare the performance of half wave rectifier and voltage double

circuits for generation of high DC voltages.

(b) A 10 stage Cockroft -Walton circuit has all capacitors of 0.1 ?F. The secondary

voltage of supply transformer is 11 kV at a frequency of 50 Hz. If the load current is 2 mA, find

i. the voltage regulation

ii. ripple voltage.


5. Discuss various capacitance, potential dividers and compare their performance for measurement of impulse voltages?


6. (a) Explain the different theories of charge formation in clouds?

(b) What are the mechanisms by which lightning strokes develop and induce over voltages on overhead power lines?


7. Explain the concept of apparent charge in partial discharge measurements. Describe a simple experiment technique to measure partial discharge.


8. Mention the different electrical tests done on isolators and circuits breakers.

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