Circuit Breakers MCQs

31. The making current of 3-phase breaker with rating 2000 MVA, 33 kV will be

1. 35 A
2. 50 A
3. 70 kA
4. 89 A

32. An air blast circuit breaker is usually employed for

1. Instantaneous voltage
2. Intermittent duty
3. Repeated duty
4. Short duty

33. The recovery voltage that appears across the circuit breaker contacts will be maximum for power factor of

1. Zero
2. 0.5
3. 0.707
4. Unity

34. Air used in air blast circuit breaker must

1. Be free from moisture
2. Have least CO₂
3. Be ionized
4. Have oil mist

35. Breaking capacity of a circuit breaker is usually expressed in

1. Volts
2. Amperes
3. MVA
4. MW

36. In the event of a fault on the connected circuit, a circuit breaker will operate

1. Automatically
2. Manually
3. Manually through a control switch
4. Depending on the design

37. Which of the following is not a part of the circuit breaker?

1. Operating mechanism
2. Conservator
3. Explosion pot
4. Fixed and moving contacts

38. In a circuit breaker, ionization is not facilitated by

1. Material of contacts
2. Increase of mean path
3. Increase of field strength
4. High temperature of surrounding medium

39. At electric breakdown

1. Conductor become insulator
2. Insulator becomes conductor
3. Semiconductor becomes conductor
4. Conductor becomes superconductor

40. In the case of circuit breakers if the length of arc increases, its resistance is

1. Decreases
2. Increases
3. Remain same
4. Some times increases or decreases