IMPORTANT QUESTIONS OF CIRCUIT BREAKERS

IMPORTANT QUESTIONS OF CIRCUIT BREAKERS:

1. What is a circuit breaker ? Describe its operating principle.

2. Discuss the arc phenomenon in a circuit breaker.

3. Explain the various methods of arc extinction in a circuit breaker.

4. Define and explain the following terms as applied to circuit breakers :

(i) Arc voltage

(ii) Restriking voltage

(iii) Recovery voltage

5. Describe briefly the action of an oil circuit breaker. How does oil help in arc extinction ?

6.Discuss the advantages and disadvantages of oil circuit breakers.

7. Explain with neat sketches the construction and working of the following circuit breakers :

(i) Plain explosion pot

(ii) Cross jet explosion pot

(iii) Self-compensated explosion pot

8. Explain the difference between bulk oil circuit breakers and low-oil circuit breakers.

9. Discuss the constructional details and operation of a typical low-oil circuit breaker ? What are its relative merits and demerits ?

10. Discuss the principle of operation of an air-blast circuit breaker. What are the advantages and disadvantages of using air as the arc quenching medium ?

11. Explain briefly the following types of air-blast circuit breakers :

(i) Axial-blast type

(ii) Cross-blast type

12. What are the important components common to most of circuit breakers ? Discuss each component briefly.

13. Write a short note on the rate of re-striking voltage:indicating its importance in the arc extinction.

14. Discuss the phenomenon of

(i) Current chopping

(ii) Capacitive current breaking

15. Write short notes on the following :

(i) Resistance switching

(ii) Circuit breaker ratings

(iii) Circuit interruption problems

16. Why do plain break oil circuit breakers have a low speed of circuit interruption ?

17. Is it logical to express the breaking capacity of a circuit breaker in MVA ? Discuss.

18. Why is current, interruption easier in an a.c. circuit than in a d.c. circuit ?

19. Why are circuit breakers designed to have a short-time rating ?

20. Is arc production in a circuit breaker unfortunate mainfestation ?

Updated: May 15, 2019 — 11:00 am