400 Important Transformer MCQ Question and Answer | PDF Free Download
1.When a transformer is operating on no load, the primary applied voltage is approximately balanced by
- APrimary induced emf
- BSecondary induced emf
- CTerminal voltage across the secondary
- DVoltage drop across the resistance and reactance
2.In the transformer circuit mode, the core loss is represented as a
- ASeries resistance
- BSeries inductance
- CShunt resistance
- DShunt inductance
3.Full load voltage regulation of a power transformer is zero when power factor of the load is near
- AUnity and leading
- BZero and leading
- CZero and lagging
- DUnity and lagging
4.In a transformer, zero voltage regulation at full load is
- ANot possible
- BPossible at leading power factor load
- CPossible at lagging power factor load
- DPossible at unity power factor load
5.Positive voltage regulation of a transformer is an indication of ____load
- AInductive
- Bcapacitive
- CEither inductive or capacitive
- DPure resistive
6.If the percentage resistance of a power transformer for secondary side si 2.5 percent and turn ratio is 1:10 , the percentage secondary resistance referred to primary will be
- A25
- B2.5
- C0.25
- D0.025
7.In a power transformer, iron loss remain practically constant from no load ot full load. This is because
- ACore flux remains constant
- BLeakage flux remains constant
- CBoth a and b
- DNeither a nor b
8.In a power transformer, if in place of sinusoidal wave, a peaked wave voltage is fed to the primary
- ACopper losses will be less
- BNoise level will be reduced
- CIron losses will be more
- DIron losses will be less
9.The full load copper loss and iron loss of a transformer are 6,400 W and 5,000 W respectively. The copper loss and iron loss at half load will be respectively
- A3,200 W and 2,500 W
- B3,200 W and 5,200W
- C1,600 W and 1,250W
- D1,600W and 5,000w
10.If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then
- ABoth hysteresis loss and eddy current loss in the core will increase
- BHysteresis loss will increase by eddy current loss will decrease
- CHysteresis loss will decrease but eddy current loss will increase
- DHysteresis loss will decrease but eddy current loss will remain unchanged
11.The total iron loss in a transformer core at normal flux density was measured at 25 Hz and at 50 Hz and was found to be 250W and 800 W respectively. The hysteresis loss at 50Hz would be
- A100 W
- B150 W
- C200 W
- D600 W
12.The main purpose of performing open circuit on a transformer is to measure its
- ACopper loss
- BCore loss
- CTotal loss
- DInsulation resistance
13.Open circuit test in a transformer is performed with
- ARated transformer voltage
- BRated transformer current
- CDirect current
- DHigh frequency supply
14.The open circuit test on a transformer is usually performed by exciting the low voltage winding. This is because
- AIt draws sufficiently large no load current which can be conveniently measured
- BThe required power input is low
- CIt is not advisable to work on high voltage size
- DThe voltage required is low.
15.The open circuit test on a transformer gives
- AEquivalent resistance and leakage reactance
- BMagnetizing current and core loss at rated voltage
- CCopper losses
- DBoth b and c
16.In transformers, which of the following statements is valid?
- AIn an open-circuit test, copper losses are obtained while in short-circuit test, core losses are obtained
- BIn an open-circuit test, current is drawn at high power factor
- CIn a short-circuit test, current is drawn at zero power factor
- DIn an open-circuit test, current is drawn at low power factor
17.During short-circuit test of a transformer, core losses are negligible because
- Athe voltage applied on the primary side is low
- Bthe current on the secondary side is rated current
- Cthe voltage on the secondary side is zero
- Dfull-load current is not supplied to the transformer
18.While performing the open circuit and short circuit tests on a transformer to determine parameters the status of the low voltage (LV) and high voltage (HV) windings will be such that
- AIn OC, LV is open and in SC HV is shorted
- BIn OC, HV is open and in SC LV is shorted
- CIn OC, LC is open and in SC LV is shorted
- DIn OC, HV is open and in SC HV is shorted
19.For a transformer to be tested at full load conditions but consuming only losses form the mains, we do
- ALoad test
- BOpen circuit and short circuit tests
- CBack to back test
- DNone of the above
20.The efficiency of two identical transformers under load conditions can be determined by
- ABack to back test
- BOpen circuit test
- CShort circuit test
- DAny of the above