Page 599 - Basic Electrical Engineering
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c. The core is made of solid steel
d. The core is made of copper laminations.
5. The no-load current of a 10 kVA, 230 V/115 V transformer wire will be about
a. 5 per cent of its rated current
b. 20 per cent of its rated current
c. 30 per cent of its rated current
d. 0.1 per cent of its rated current.
6. The no-load current of a 15 kVA, 230/1100 V single-phase transformer will be about
a. 15.33 A
b. 3 A
c. 12 A
d. 73.3 A.
7. Efficiency of a transformer is higher tham that of a motor or a generator of similar rating
because
a. There is no hysteresis and eddy current loss in a motor or a generator
b. Designs of transformers are superior than motors and generators
c. Transformer is a static device and there is no rotational loss in it
d. Transformers are connected to high-voltage transmission lines whereas motors and
generators are connected to low-voltage supply lines.
8. Which of the following losses in a transformer vary with load
a. Hysteresis loss
b. Eddy current loss
c. Copper losses in the windings
d. Iron loss.
9. Open-circuit test and short-circuit test on a transformer are performed to determine,
respectively, the following losses
a. Copper loss and core loss
b. Core loss and copper loss
c. Eddy current loss and hysteresis loss
d. Hysteresis loss and eddy current loss.
10. Maximum efficiency of a transformer is obtained at a load at which its
a. Core loss becomes the minimum
b. Copper loss becomes the minimum
c. Copper loss equals core loss
d. Core loss becomes negligible.
