Electrical Transformers Objective Questions and Answers - ObjectiveBooks

Electrical Transformers Objective Questions and Answers

Practice Test: Question Set - 16


1. Which of the following statements regarding an idle single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect ?
    (A) Its secondary current is 5 A
    (B) Its secondary voltage is 400 V
    (C) Its rating is 2 kVA
    (D) Its secondary current is 20 A

2. No-load on a transformer is carried out to determine
    (A) Copper loss
    (B) Magnetizing current
    (C) Magnetizing current and loss
    (D) Efficiency of the transformer

3. In the transformer following winding has got more cross-sectional area
    (A) Low voltage winding
    (B) High voltage winding
    (C) Primary winding
    (D) Secondary winding

4. Efficiency of a power transformer is of the order of
    (A) 100 percent
    (B) 98 percent
    (C) 50 percent
    (D) 25 percent

5. The maximum efficiency of a distribution transformer is
    (A) At no load
    (B) At 50% full load
    (C) At 80% full load
    (D) At full load

6. No-load current of a transformer has
    (A) Has high magnitude and low power factor
    (B) Has high magnitude and high power factor
    (C) Has small magnitude and high power factor
    (D) Has small magnitude and low power factor

7. The chemical used in breather for transformer should have the quality of
    (A) Ionizing air
    (B) Absorbing moisture
    (C) Cleansing the transformer oil
    (D) Cooling the transformer oil

8. The function of conservator in a transformer is
    (A) To project against internal fault
    (B) To reduce copper as well as core losses
    (C) To cool the transformer oil
    (D) To take care of the expansion and contraction of transformer oil due to variation of temperature of surroundings

9. The magnetizing current of a transformer is usually small because it has
    (A) Small air gap
    (B) Large leakage flux
    (C) Laminated silicon steel core
    (D) Fewer rotating parts

10. Harmonics in transformer result in
    (A) Increased core losses
    (B) Increased I2R losses
    (C) Magnetic interference with communication circuits
    (D) All of the above

11. Power transformers are generally designed to have maximum efficiency around
    (A) No-load
    (B) Half-load
    (C) Near full-load
    (D) 10% overload

12. An ideal transformer will have maximum efficiency at a load such that
    (A) Copper loss = iron loss
    (B) Copper loss < iron loss
    (C) Copper loss > iron loss
    (D) None of the above

13. Which type of winding is used in 3 phase shell-type transformer?
    (A) Circular type
    (B) Sandwich type
    (C) Cylindrical type
    (D) Rectangular type

14. A shell-type transformer has
    (A) High eddy current losses
    (B) Reduced magnetic leakage
    (C) Negligibly hysteresis losses
    (D) None of the above

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