Transformers Electrical Engineering Quiz | Transformers Electrical Engineering Objective Type Questions and Answers

Questions
21 In a transformer the tappings are generally provided on
A primary side
B secondary side
C low voltage side
D high voltage side

Answer: low voltage side
22 If the percentage impedances of the two transformers working in parallel are different, then
A transformers will be overheated
B power factors of both the transformers will be same
C parallel operation will be not possible
D parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load

Answer: parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load

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23 What will happen if the transformers working in parallel are not connected with regard to polarity ?
A The power factor of the two trans-formers will be different from the power factor of common load
B Incorrect polarity will result in dead short circuit
C The transformers will not share load in proportion to their kVA ratings
D none of the above

Answer: Incorrect polarity will result in dead short circuit
24 If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be
A R2/VK
B R2IK2
C R22!K2
D R22/K

Answer: R2IK2
25 Two transformers operating in parallel will share the load depending upon their
A leakage reactance
B per unit impedance
C efficiencies
D ratings

Answer: per unit impedance
26 The power transformer is a constant
A voltage device
B current device
C power device
D main flux device

Answer: main flux device
27 The purpose of providing iron core in a step-up transformer is
A to provide coupling between primary and secondary
B to increase the magnitude of mutual flux
C to decrease the magnitude of mag-netizing current
D to provide all above features

Answer: to decrease the magnitude of mag-netizing current
28 Greater the secondary leakage flux
A less will be the secondary induced e.m.f.
B less will be the primary induced e.m.f.
C less will be the primary terminal voltage
D none of the above

Answer: less will be the secondary induced e.m.f.
29 Spacers are provided between adjacent coils
A to provide free passage to the cooling oil
B to insulate the coils from each other
C both (a) and (b)
D none of the above

Answer: to provide free passage to the cooling oil
30 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

Answer: has small magnitude and low power factor
31 Transformer breaths in when
A load on it increases
B load on it decreases
C load remains constant
D none of the above

Answer: load on it decreases
32 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

Answer: at 50% full load
33 Power transformers are designed to have maximum efficiency at
A nearly full load
B 70% full load
C 50% full load
D no load

Answer: nearly full load
34 Natural oil cooling is used for transformers up to a rating of
A 3000 kVA
B 1000 kVA
C 500 kVA
D 250 kVA

Answer: 3000 kVA
35 In the transformer the function of a conservator is to
A provide fresh air for cooling the transformer
B supply cooling oil to transformer in time of need
C protect the transformer from damage when oil expends due to heating
D none of the above

Answer: protect the transformer from damage when oil expends due to heating
36 In a transformer routine efficiency depends upon
A supply frequency
B load current
C power factor of load
D both (b) and (c)

Answer: both (b) and (c)
37 The no load current in a transformer lags behind the applied voltage by an angle of about
A 180°
B 120″
C 90°
D 75°

Answer: 75°
38 A common method of cooling a power transformer is
A natural air cooling
B air blast cooling
C oil cooling
D any of the above

Answer: oil cooling
39 In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are
A friction and windage losses
B copper losses
C hysteresis and eddy current losses
D none of the above

Answer: hysteresis and eddy current losses
40 Efficiency of a power transformer is of the order of
A 100 per cent
B 98 per cent
C 50 per cent
D 25 per cent

Answer: 98 per cent
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