1) A 10 kVA, 2000 / 100v transformer has R1=1.5 ohm, R2=0.005 ohm, X1=2.5 ohm and X2=0.08 ohm. The equivalent resistance referred to primary is
a. 3 ohm
b. 3.25 ohm
c. 3.5 ohm
d. 3.8 ohm
Answer
Explanation

ANSWER: 3.5 ohm
Explanation: No explanation is available for this question!


2) A 5kV / 250V, 50Hz single phase core type transformer with average flux in the core is 0.05wb. The number of turns in the primary winding is
a. 273
b. 278
c. 280
d. 287
Answer
Explanation

ANSWER: 287
Explanation: No explanation is available for this question!


3) A 600kVA transformer has core losses of 1w at 25 Hz and 2.5w at 50 Hz (neglecting resistances and assuming flux density to be constant). The power required at 60 Hz is
a. 3 watt
b. 3.5 watt
c. 3.24 watt
d. 3.54 watt
Answer
Explanation

ANSWER: 3.24 watt
Explanation: No explanation is available for this question!


4) A transformer when connected to a 230V, 50Hz supply, under no load draws a current of 4A at a power factor of 0.2 lagging. The magnetizing current (I_{m}) and core loss (P_{c}) is equal to
a. 3.919A, 184W
b. 1.84A, 391.9W
c. 39.19A, 184W
d. 3A, 180W
Answer
Explanation

ANSWER: 3.919A, 184W
Explanation: No explanation is available for this question!


5) When a transformer is supplied by full load at 0.8 p.f. lagging its copper losses is given by P_{cu}. if it is supplied by half load then copper losses will be
a. P _{cu}
b. 2P _{cu}
c. P _{cu} / 2
d. P _{cu} / 4
Answer
Explanation

ANSWER: P_{cu} / 4
Explanation: No explanation is available for this question!


6) 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!


7) 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!


8) 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!


9) 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!


10) 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!

