Q.1
When will be the efficiency of a transformer maximum?
  • a) Copper losses = hysteresis losses
  • b) Hysteresis losses = eddy current losses
  • c) Eddy current losses = copper losses
  • d) Copper losses = iron losses
Q.2
Efficiency of a power transformer is near to the ___________
  • a) 100 per cent
  • b) 98 per cent
  • c) 50 per cent
  • d) 25 per cent
Q.3
On which factors transformer routine efficiency depends upon?
  • a) Supply frequency
  • b) Load current
  • c) Power factor of load
  • d) Load current and power factor of load
Q.4
Normal transformers are designed to have maximum efficiency at ___________
  • a) Nearly full load
  • b) 70% full load
  • c) 50% full load
  • d) No load
Q.5
At which load condition maximum efficiency of a distribution transformer will be achieved?
  • a) At no load
  • b) At 60% full load
  • c) At 80% full load
  • d) At full load
Q.6
Power transformers other than distribution transformers are generally designed to have maximum efficiency around ______
  • a) No-load
  • b) Half-load
  • c) Near full-load
  • d) 10% overload
Q.7
For a transformer given, operating at constant load current, maximum efficiency will occur at ______
  • a) 0.8 leading power factor
  • b) 0.8 lagging power factor
  • c) Zero power factor
  • d) Unity power factor
Q.8
Why efficiency of a transformer, under heavy loads, is comparatively low?
  • a) Copper loss becomes high in proportion to the output
  • b) Iron loss is increased considerably
  • c) Voltage drop both in primary and secondary becomes large
  • d) Secondary output is much less as compared to primary input
Q.9
The efficiencies of transformers compared to electric motors of the same power are ___________
  • a) About the same
  • b) Much smaller
  • c) Much higher
  • d) Can’t comment
Q.10
A transformer having maximum efficiency atfull load will have ratio of iron loss and full load copper loss equal to ___________
  • a) 4/3
  • b) 3/4
  • c) 9/16
  • d) 16/9
Q.11
What is the correct formula of efficiency of a device?
  • a) Input /output
  • b) Output/losses
  • c) 1- (losses/ (output + losses))
  • d) Cannot be determined
Q.12
AkVA transformer is having efficiency ofat full load and also atof full load; both at unity power factor. Then Pi is ___________
  • a) 16.45 kW
  • b) 9.87 kW
  • c) 14.57 kW
  • d) Can’t be calculated
Q.13
AkVA transformer is having efficiency ofat full load and also atof full load; both at unity power factor. Then Pc is ___________
  • a) 16.45 kW
  • b) 9.87 kW
  • c) 14.57 kW
  • d) Can’t be calculated
Q.14
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 the efficiency?
  • a) 86.44%
  • b) 96.44%
  • c) 97.44%
  • d) 99.12%
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