Circuit Breakers(Engineering > Electrical Engineering ) Questions and Answers

Question 1. In a circuit breaker the active recovery voltage depends upon
  1.    power factor
  2.    armature reaction
  3.    circuit conditions
  4.    all of the above
Explanation:-
Answer: Option D. -> all of the above


all of the above


Question 2. The transient voltage that appears across the contacts at the instant of arc extinction is called
  1.    recovery voltage
  2.    re striking voltage
  3.    supply voltage
  4.    peak voltage
Explanation:-
Answer: Option B. -> re striking voltage


re striking voltage


Question 3. In a circuit breaker if the insulation resistance between phase terminal and earthed frame is less than the specified limit, the probable cause could be
  1.    moisture
  2.    dirty insulation surface
  3.    carbon or copper particles sticking to the internal surface
  4.    any of the above
Explanation:-
Answer: Option D. -> any of the above


any of the above


Question 4. The normal frequency rms voltage that appears across the breaker poles after final arc extinction has occurred, is
  1.    recovery voltage
  2.    re striking voltage
  3.    supply voltage
  4.    peak voltage
Explanation:-
Answer: Option A. -> recovery voltage


recovery voltage


Question 5. If a circuit breaker does not operate on electrical compound, the probable reason could be
  1.    spring defective
  2.    trip circuit open
  3.    trip latch defective
  4.    any of the above
Explanation:-
Answer: Option D. -> any of the above


any of the above


Question 6. The contact resistance of a circuit breaker is. of the order of
  1.    20 micro ohms ± 10
  2.    20 milli ohms ± 10
  3.    20 ohms ± 10
  4.    200 ohms ± 10
Explanation:-
Answer: Option A. -> 20 micro ohms ± 10


20 micro ohms ± 10


Question 7. Which of the following circuit breakers does not use pneumatic operating mechanism
  1.    Air blast circuit breaker
  2.    SF6 blast circuit breaker
  3.    Air break circuit breaker
  4.    Bulk-oil circuit breaker
Explanation:-
Answer: Option D. -> Bulk-oil circuit breaker


Bulk-oil circuit breaker


Question 8. There is definite objection to use of which of the following medium for extinguishing the arc in case of a circuit breaker ?
  1.    Air
  2.    SF6 gas
  3.    Vacuum
  4.    Water
Explanation:-
Answer: Option D. -> Water


Water


Question 9. The insulation resistance of high voltage circuit breaker is
  1.    1k Ohm
  2.    10 k Ohm
  3.    20 Mega ohms
  4.    2000 Mega ohm
Explanation:-
Answer: Option D. -> 2000 Mega ohm


2000 Mega ohm


Question 10. Fusing factor for a HRC fuse is
  1.    Minimum fusing current / Current rating
  2.    Minimum fusing current / Minimum rupturing time
  3.    Maximum fusing current / Minimum fusing current
  4.    Minimum fusing current / Prospective current of circuit
Explanation:-
Answer: Option A. -> Minimum fusing current / Current rating


Minimum fusing current / Current rating


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