Sunday, September 13, 2020

Chapter 7: Transformer- Single and Three phase-Page 7

 Chapter 7: Transformer- Single and Three phase

61. In Scott connections, the neutral point divides the teaser winding in the ratio
A.1:3
B.1:2
C.1:1
D.1:4


... Answer is (B)

 

 
 

62. The secondary line voltage is maximum for which of the following connection?
A. delta-delta
B. star-star
C. delta-star
D. star-delta

... Answer is (C)

 
 
 

63. Three units of 15 transformers are connected in A?V to supply a 3-phase load from a 400 V. 3. source. The line voltage on the load side is
A. 1000 V
B. 80 V
C. 3464 V
D. 803 V

... Answer is (C)

 

 
 

64. The secondary of a PT is generally designed for
A. 220 V
B. 110 V
C. 150V
D. 11 V

  ... Answer is (B)

 

 
 
65. The secondary of a CT is generally designed for
A. 100 A
B. 10 A
C. 5 A
D. 0.5 A
  ...
Answer is (C)

 
 
 

66. The maximum efficiency of a 100 kVA transformer having iron loss of 900 kW and F.L. Cu loss of 1600 W occurs at
A. 56.3 kVA
B. 133.3 kVA
C. 75 kVA
D. 177.7 kVA

  ... Answer is (C)

 

 
 

67. A good voltage regulation of a transformer means
A. difference between primary and secondary voltage is least
B. difference between primary and secondary voltage is maximum
C. output voltage fluctuation with power factor is the least
D. output voltage fluctuation form no load to full load is least.

... Answer is (D)

 
 

68. Test used to determine the efficiency of two identical transformers at full load is
A. Open-circuit test
B. Short circuit test
C. Type tests
D. Back to back test

... Answer is (D)

 
 

69. A 220/115 V, 25 Hz, 1-phase transformer has eddy current loss of 100 watt which is half of the no-load loss at rated applied voltage. If this transformer is used with primary connected to a 440 V, 50 V, 50 Hz mains, the total no-load loss would be
A. 300 W
B. 600 W
C. 1000 W
D. 400 W

 
  ... Answer is (B)

 
 

70.  If Cu loss of a transformer at 7/8th full load is 4900 W, then its full-load Cu loss would be
A. 5600 watts
B. 6400 watts
C. 375 watts
D. 429 watts

  ... Answer is (B)

 

 

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