1. If the input frequency of a transformer is increases then its secondary induced emf
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above. Answer
2. The main purpose of using shell type transformer is to reduce
(a) hysteresis losses.
(b) eddy current losses.
(c) magnetic leakage.
(d) size of transformer. Answer
3. A transformer has full load copper losses of 600 watt, the copper losses at half load will be
(a) 150 watt.
(b) 300 watt.
(c) 600 watt.
(d) 1200 watt. Answer
4. A transformer has 400 watt iron losses at full load, the iron loss at half load will be
(a) 100 watt.
(b) 200 watt.
(c) 400 watt.
(d) 800 watt. Answer
5. A Buchholz relay can be installed on
(a) auto-transformers.
(b) air-cooled transformers.
(c) oil cooled transformers.
(d) any of the above. Answer
6. Which of the following electrical machines have maximum efficiency?
(a) Induction motor.
(b) DC motor ultimate.
(c) Power transformer.
(d) Alternator. Answer
7. Harmonics in transformer result in
(a) increased core losses.
(b) increased I2R losses.
(c) magnetic interference with communication circuits.
(d) all of the above. Answer
8. While performing open circuit test on a transformer, the primary is supplied with
(a) rated voltage.
(b) rated current.
(c) reduced voltage.
(d) over voltage. Answer
9. Which winding of the transformer has less cross-sectional area?
(a) primary winding.
(b) secondary winding.
(c) low voltage winding.
(d) high voltage winding. Answer
10. With the increase in magnitude of the leakage flux, the magnitude of main flux in the core of transformer is
(a) increases.
(b) decreases.
(c) remain unchanged.
(d) none of the above. Answer
11. The effect of leakage flux in transformer will result in
(a) more copper losses.
(b) more voltage drop.
(c) less copper losses.
(d) less voltage drop. Answer
12. When a given transformer is run at its rated voltage but reduced frequency, its
(a) flux density remains unaffected.
(b) iron losses are reduced.
(c) core flux density is reduced.
(d) core flux density is increased. Answer
13. Which of the following device is used to take up the expansion of oil due to temperature rise?
(a) Breather.
(b) Conservator tank.
(c) Radiator.
(d) Buchholz relay. Answer
14. Which of the following 3-phase connection of a transformer causes interface with the neighboring communication line?
(a) star-delta.
(b) delta-star.
(c) delta-delta.
(d) star-star. Answer
15. Ferrite core are used in high frequency transformers because it has
(a) high specific gravity.
(b) high resistance.
(c) low resistance.
(d) low permeability. Answer