400 Important Transformer MCQ Question and Answer | PDF Free Download
1.The efficiency of a power transformer can be determined indirectly by
- AOpen circuit test alone
- BShort circuit test alone
- COpen circuit and short circuit tests
- DBack to back test
2.The transformer efficiency at relatively light loads is quite low. This is due to
- ASmall copper losses
- BSmall secondary output
- CHigh fixed loss in comparison to the output
- DPoor power factor
3.The transformer efficiency, under heavy loads is comparatively low because
- Acopper loss becomes high in comparison to the output
- BLarge increase in iron losses
- CDrop in power factor
- DNone of the above
4.The efficiency of a 100 kVA transformer is 0.98 at full as well as half load. For this transformer at full load the copper loss
- AIs less than core less
- BIs equal to core loss
- CIs more than corer loss
- DNone of the above
5.The efficiency of a transformer will be maximum when
- AHysteresis loss = copper loss
- BEddy current loss= copper loss
- CCopper loss= iron loss
- DHysteresis loss = copper loss
6.Power transformers are designed to have maximum efficiency at
- ANearly full load
- Bhalf load
- CNo Load
- DLittle more than full load
7.The transformer efficiency will be maximum at a power factor of
- A0.8 lead
- BUnity
- C0.8 lag
- D0.5 lead or lag
8.If P1 and P2 be the iron and copper losses of a transformer at full load and the maximum efficiency is at 75 % of the full load, then what is the ratio of P1 and P2?
- A9/16
- B10/16
- C?
- D3/16
9.What is load at which maximum efficiency occurs in case of a 100 kVA transformer with iron loss of 1 kW and full load copper loss of 2 kW?
- A100 kVA
- B70.7 kVA
- C50.5 kVA
- D25.2 kVA
10.A 500 kVA transformer has constant loss of 500 W and copper losses at full load are 2,000W. Then at what load, is the efficiency maximum?
- A250 KVA
- B500 KVA
- C1000 KVA
- D125 KVA
11.A 2 kVA transformer has iron loss of 150 W and full load coper loss of 250 W. The maximum efficiency of the transformer would occur when the total loss is
- A500 W
- B400 W
- C300 W
- D275 W
12.The all-day efficiency of a distribution transformer will be high with low
- ACopper losses
- BIron losses
- COperating temperature
- DCopper as well as iron losses
13.The all-day efficiency of a transformer depends primarily on
- AIts copper loss
- BThe amount of load
- CThe duration of load
- DBoth the amount and duration of load
14.The desirable properties of transformer core material are
- ALow permeability and low hysteresis loss
- BHigh permeability and high hysteresis loss
- C High permeability and low hysteresis loss
- DLow permeability and high hysteresis loss
15.The use of higher flux density in the transformer design
- AReduces the weight per kVA
- BIncreases the weight per kVA
- CHas no relation with the weight of transformer
- DIncreases the weight per KW
16.What does the use of higher flux density value in a transformer design lead to
- AIncrease in weight per kVA
- BDecrease in weight per kVA
- CReduced iron losses
- DReduced copper losses
17.The size of the transformer core depends upon
- AFrequency
- BPermissible flux density in the core material
- CArea of the core
- DBoth (a) and (b)
18.Ferrite cores are employed in high frequency transformer because it has
- ALow resistance
- BHigh resistance
- CLow permeability
- DHigh hysteresis loss
19.What is the core loss in a high frequency ferrite core transformer used in SMPS power supply?
- A10% of rated power
- B5% rated power
- C2% of rated power
- D1% of rated power
20.Cores of large power transformers are made from which one of the followings?
- AHot rolled steel
- BCold rolled non grain-oriented steel
- CCold rolled grain-oriented steel
- DFerrite