Transformer - Electrical Engineering (MCQ) questions and answers

1)   When a transformer is supplied by full load at 0.8 p.f. lagging its copper losses is given by Pcu. if it is supplied by half load then copper losses will be

a. Pcu
b. 2Pcu
c. Pcu / 2
d. Pcu / 4
Answer  Explanation 

ANSWER: Pcu / 4

Explanation:
No explanation is available for this question!


2)   In a 20 kVA, 2200 / 220 volts transformer iron and copper losses are 300 and 400 watts respectively. Its efficiency at half load and unity power factor is

a. 95.11%
b. 96.15%
c. 97.77%
d. 98%
Answer  Explanation 

ANSWER: 96.15%

Explanation:
No explanation is available for this question!


3)   A 600 kVA transformer has iron losses of 400 kW and copper losses of 500 kW. Its kVA rating for maximum efficiency is given by

a. 537 kVA
b. 548 kVA
c. 555 kVA
d. 585 kVA
Answer  Explanation 

ANSWER: 537 kVA

Explanation:
No explanation is available for this question!


4)   When a resistance is to be transferred from primary to secondary side of transformer with the turns ratio as k, it must be

a. Multiplied by k ∧ 2
b. Multiplied by k
c. Divided by k
d. Divided by k ∧ 2
Answer  Explanation 

ANSWER: Multiplied by k ∧ 2

Explanation:
No explanation is available for this question!


5)   In double delta transformation, a double delta refers to the case where there are two delta transformations in

a. Parallel
b. Series
c. Both series and parallel
d. Neither series nor parallel
Answer  Explanation 

ANSWER: Series

Explanation:
No explanation is available for this question!


6)   In a 5 kV / 400V, 75 kVA single phase transformer, the current flowing in the primary winding of transformer is 10A. what will be the current flowing in the secondary winding?

a. 100A
b. 120A
c. 125A
d. 130A
Answer  Explanation 

ANSWER: 125A

Explanation:
No explanation is available for this question!


7)   In T-T connection, the ratio of actual capacity to the available capacity is

a. 1
b. 0.928
c. 1.928
d. 0.5
Answer  Explanation 

ANSWER: 0.928

Explanation:
No explanation is available for this question!


8)   Whether the given autotransformer is step up or step down, its VA rating is always

a. Greater than the two winding transformer
b. Equal to the two winding transformer
c. lesser than the two winding transformer
d. cannot say
Answer  Explanation 

ANSWER: Greater than the two winding transformer

Explanation:
No explanation is available for this question!


9)   In an autotransformer if the power transferred inductively is equal to the power conducted through, then transformation ratio is given by

a. 1
b. 0.5
c. 2
d. 0
Answer  Explanation 

ANSWER: 0.5

Explanation:
No explanation is available for this question!


10)   If a two winding transformer is converted into an autotransformer  by applying additive polarity and subtractive polarity which results in the secondary voltages of 1840 and 1810 volts. Then the primary and secondary voltages of transformer are

a. 1800V, 50V
b. 1810V, 40V
c. 1820V, 30V
d. 1825V, 15V
Answer  Explanation 

ANSWER: 1825V, 15V

Explanation:
No explanation is available for this question!


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