a) true
b) false

Ans: (b)

a) Copper losses are half of the iron losses
b) Copper losses are equal to iron losses
c) Copper losses are negligible in comparison to iron losses
d) Iron losses are zero

Ans: (b)

a) full load × (iron loss)/(f.l.cu-loss)
b) full load × ((iron loss)²)/(f.l.cu-loss)
c)full load × √((iron loss)/(f.l.cu-loss))
d) full load × √((f.l.cu-loss)/(iron loss))

Ans: (c)

a) The primary of such transformers is energized for all twenty-four hours and core losses occur throughout the day whereas copper losses will occur only when secondary is supplying load
b) Core losses are always more than copper losses
c) Core losses may destroy the insulation
d) Core losses will heat up the oil of the transformer rapidly

Ans: (a)

a) true
b)false

Ans: (b)

a) The percentage impedance should be equal
b) The transformers should be properly connected with regard in polarity
c) The primary winding of the transformers should be suitable for the supply system voltage and frequency
d) The voltage ratings of transformers of primary and secondary winding should be identical

Ans: ()

a) Incorrect polarity will result in dead short-circuit
b) The transformers will not share load in proportion to their KVA rating
c) The power factors of two transformers will be different from the power factor of common load
d) None of the above

Ans: (a)

a) Parallel operation will not be possible
b) Parallel operation will still be possible, but the power factors at which the two
transformers operate will be different from the power factor of the common load
c) Transformers will be over heated
d) Power factors of both of the transformers will be same

Ans: (b)

a) Delta-delta connection
b) Star-star connection
c)Star-delta connection
d)Delta-star connection

Ans: (b)

a) true
b) false

Ans: (a)

a) true
b) false

Ans: (a)

a) To accomplish three phase to three phase transformation only
b) To accomplish three phase to two phase transformation only
c) To accomplish three phase to three phase and three phase to two phase transformation
d) None of the above

Ans: (c)

a) 10% greater than teaser transformer
b) 15% greater than teaser transformer
c) 57.7% greater than teaser transformer
d) 66.6% greater than teaser transformer

Ans: (b)

a) true
b) false

Ans: (a)

a) K/√3
b) √(3/2K)
c) 2K/√3
d) √(K/2)

Ans: (c)

Related topics :