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. Explain the applications of insulating materials in the construction of circuit breakers.


2. Explain various primary ionization processes of Townsend’s mechanism. Derive an expression for current growth due to these processes.


3. Derive the expression for critical electric field and show that the field is independent of critical temperature of the dielectric. State the assumptions made.


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 the problems associated with peak voltmeter circuits using passive elements. Draw the circuit developed by Rabus and explain how this circuit overcomes these



6. Discuss the power frequency over voltages in power systems. Explain various protection schemes employed to suppress the over voltages?


7. Explain the high voltage Schering bridge for the tan ? and capacitance  measurement of insulators (or) bushings?


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

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