81. The winding used in a 3-phase shell type transformer is ______ type.
- circular
- cylindrical
- sandwich
- rectangular
82. Transformers are rated in kVA instead of kW because
- load pf is often not known
- kVA is fixed where kW depends on load pf
- total transformer loss depends on volt amperes
- it has become customary
83. Which of the following connection of transformer will give the highest secondary voltage?
- delta primary, delta secondary
- delta primary, star secondary
- star primary, star secondary
- star primary, delta secondary
84. In a properly connected star-delta transformer, a voltmeter connected in the secondary, the voltmeter
- zero voltage
- line voltage of supply
- phase voltage in the secondary
- none of the above
85. Which of the following 3-phase connections of a transformer causes interference to the nearby communication systems?
- delta-star
- star-delta
- star-star
- delta-delta
86. Scott connections are used for
- single phase to three phase transformation
- three phase to single phase transformation
- three phase to two phase transformation
- any of the above
87. In a transformer fed from a fundamental frequency voltage source, the source of harmonics is the
- overload
- poor insulation
- iron loss
- saturation of core
88. In which transformer, the tertiary winding is used?
- star-star
- delta-delta
- star-delta
- delta-star
89. The magnetizing current in a transformer is rich in
- 3rd harmonic
- 5th harmonic
- 7th harmonic
- 13th harmonic
90. Which of the following conditions are necessary for the parallel operation of two transformers?
- percentage impedance should be same
- polarities of both secondary’s should be same
- voltage ratings should be same
- all the conditions mentioned above