Electrical Machine - I (3140913) MCQs

MCQs of Transformers

Showing 91 to 100 out of 155 Questions
91.
The primary reason why the open-circuit test is performed on the low-voltage winding of the transformer is that it
(a) draws sufficiently large on-load current for convenient reading
(b) requires the least voltage to perform the test
(c) needs a minimum power input
(d) involves less core loss
Answer:

Option (a)

92.
The short circuit test on a transformer is conducted to obtain
(a) Copper loss at full load
(b) Copper loss at any load
(c) Copper loss at half load
(d) Copper loss at overload
Answer:

Option (b)

93.
During the short-circuit test, the iron loss of a transformer is negligible because
(a) the entire input is just sufficient to meet Cu losses only
(b) flux produced is a small fraction of the normal flux
(c) iron core becomes fully saturated
(d) supply frequency is held constant
Answer:

Option (b)

94.
For a 1.15 kVA 230/460V transformer connected to a standard 1–phase 230V supply, the no-load current likely to be
(a) 0.2 A
(b) 2.5 A
(c) 1 A
(d) 5 A
Answer:

Option (a)

95.
A transformer having a voltage ratio of 3000/300 V takes a current of 0.7 A from the primary at a power factor of 0.6 under open circuit condition. Calculate the magnetizing current of the transformer.
(a) 0.73 A
(b) 0.56 A
(c) 0.42 A
(d) 0.67 A
Answer:

Option (b)

96.
The voltage applied to the h.v. side of a transformer during the short-circuit test is 2% of its rated voltage. The core loss will be.......percent of the rated core loss.
(a) 2
(b) 0.02
(c) 4
(d) 0.04
Answer:

Option (d)

97.
Which test on a transformer provides information about regulation, efficiency, and heating under load conditions?
(a) Back to back test
(b) Open circuit test
(c) Hopkinson test
(d) Short circuit test
Answer:

Option (a)

98.
When does the Y-Y connection of a transformer work satisfactorily?
(a) Load is unbalanced only
(b) Load is balanced only
(c) On balanced as well as unbalanced loads
(d) Independent of load type
Answer:

Option (b)

99.
When does the ∆ − ∆ connected transformer work satisfactorily?
(a) Load is balanced only
(b) Load is unbalanced only
(c) On balanced as well as unbalanced loads
(d) Independent of load type
Answer:

Option (c)

100.
What is the ratio of transformation of Y-Y connection?
(a) Phase transformation X:1, line transformation X:1
(b) Phase transformation X:1, line transformation 2X:1
(c) Phase transformation X:1, line transformation X/3:1
(d) Can’t say
Answer:

Option (a)

Showing 91 to 100 out of 155 Questions