Q.1
Power transformers other than distribution transformers are generally designed to have maximum efficiency around ______
  • a) 10% overload
  • b) Near full-load
  • c) Half-load
  • d) No-load
Q.2
For a power transformer operating at full load it draws voltage and current equal toV andA respectively at 0.8 pf. Iron and copper losses are equal tokW and 300kW. What is efficiency?
  • a) 97.44%
  • b) 99.12%
  • c) 86.44%
  • d) 96.44%
Q.3
Voltage regulation of transformer is given by _____________
  • a) V2-E2/E2
  • b) V2-E2/V2
  • c) E2-V2/V2
  • d) E2-V2/E2
Q.4
No-load current in the transformer is _______
  • a) Sinusoidal distorted
  • b) Sinusoidal
  • c) Steps
  • d) Straight DC
Q.5
Which of the following is the main advantage of an auto-transformer over a two-winding transformer?
  • a) Eddy losses are totally eliminated
  • b) Copper losses are negligible
  • c) Saving in winding material
  • d) Hysteresis losses are reduced
Q.6
For a 20kVA transformer with a turn ratio of 0.4 what amount of total power is transferred inductively?
  • a) 10kVA
  • b) 8kVA
  • c) 50kVA
  • d) 12kVA
Q.7
Which of the following is the major requirement for the transformers used for electronic purposes?
  • a) Constant amplitude voltage gain
  • b) Perfect DC isolation, maximum efficiency and constant voltage gain
  • c) Perfect DC isolation
  • d) Maximum efficiency
Q.8
Which type of winding is used in 3-phase shell-type transformer?
  • a) Cylindrical type
  • b) Circular type
  • c) Rectangular type
  • d) Sandwich type
Q.9
Why shell type 3-phase transformer is used in large power transforming applications?
  • a) Due to other reasons
  • b) More height and less height flexibility
  • c) Can be made with less height
  • d) Can be made with more height
Q.10
Which of the following is not a routine test for transformers?
  • a) Polarity test
  • b) Radio interference test
  • c) Core insulation voltage test
  • d) Impedance test
Q.11
What will happen if the secondary of a current transformer is open-circuited?
  • a) depends on other parameters
  • b) cool as there is no secondary current
  • c) hot because primary will carry heavy current
  • d) hot because of heavy iron losses
Q.12
Welding transformers work on principle that weld is actually __________________
  • a) open circuit
  • b) short circuit
  • c) circuit with finite resistance
  • d) circuit with finite reactance
Q.13
Insulation of HVDC transformers should be ___________
  • a) no need of insulation
  • b) can be dry or wet
  • c) wet always
  • d) dry always
Q.14
Core flux in the transformer is _______________
  • a) square wave
  • b) triangular
  • c) sinusoidal
  • d) flat-topped
Q.15
For a transformer with primary turnssecondary turnsifV is applied at primary we will get ___________
  • a) 3200 V at secondary
  • b) 1600 V at secondary
  • c) 800 V at secondary
  • d) 80 V at secondary
Q.16
For a transformer given ofkVA, 220/6000-V transformer, short circuit test is performed. What current rating is needed?
  • a) 445A
  • b) 40A
  • c) 60A
  • d) 30A
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