Transformer - Electrical Engineering (MCQ) questions and answers

1)   A ferro resonant transformer regulation is also known as

a. Constant current transformer
b. Constant voltage transformer
c. Variable current transformer
d. Variable voltage transformer
Answer  Explanation 

ANSWER: Constant current transformer

Explanation:
No explanation is available for this question!
2)   A constant voltage transformer is fed with the sinusoidal input voltage. Its output is

a. Sinusoidal
b. Flat topped
c. Saw tooth
d. Zig-zag
Answer  Explanation 

ANSWER: Flat topped

Explanation:
No explanation is available for this question!
3)   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!
4)   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!
5)   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!
6)   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 (Im) and core loss (Pc) 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!
7)   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!
8)   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!
9)   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!
10)   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!
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