Deck 2: Transformer Technology and Design

Question 1

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 1

protect the transformer from damage when oil expends due to heating

Question 2

Natural oil cooling is used for transformers upto a rating of

A)3000 kVA
B)1000 kVA
C)500 kVA
D)250 kVA

Answer 2

3000 kVA

Question 3

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 3

nearly full load

Question 4

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

Question 5

Transformer breaths in when

A)load on it increases
B)load on it decreases
C)load remains constant
D)none of the above

Question 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 powerfactor

Question 7

Spacers are provided between adjacent coils

A)to provide free passage to the cool¬ing oil
B)to insulate the coils from each other
C)both (a) and (b)
D)none of the above

Question 8

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

Question 9

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

Question 10

The power transformer is a constant

A)voltage device
B)current device
C)power device
D)main flux device

Question 11

Two transformers operating in parallel will share the load depending upon their

A)leakage reactance
B)per unit impedance
C)efficiencies
D)ratings

Question 12

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

Question 13

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

Question 14

Ifthe percentage impedances of the two transformers working in parallel aredifferent, then

A)transformers will be overheated
B)power factors of both the trans-formers 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 tr

Question 15

In a transformer the tappings are generally provided on

A)primary side
B)secondary side
C)low voltage side
D)high voltage side

Question 16

The use of higher flux density in the transformer design

A)reduces weight per kVA
B)reduces iron losses
C)reduces copper losses
D)increases part load efficiency

Question 17

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 tr

Question 18

The chemical used in breather is

A)asbestos fibre
B)silica sand
C)sodium chloride
D)silica gel

Question 19

The transformer ratings are usually expressed in terms of

A)volts
B)amperes
C)kW
D)kVA

Question 20

The noise resulting from vibrations of laminations set by magnetic forces, is termedas

A)magnetostrication
B)boo
C)hum
D)zoom

Question 21

Hysteresis loss in a transformer varies as CBmax = maximum flux density)

A)Bmax
B)Bmax1-6
C)Bmax1-83
D)B max

Question 22

Material used for construction of transformer core is usually

A)wood
B)copper
C)aluminium
D)silicon steel

Question 23

The thickness of laminations used in a transformer is usually

A)0.4 mm to 0.5 mm
B)4 mm to 5 mm
C)14 mm to 15 mm
D)25 mm to 40 mm

Question 24

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 exp

Question 25

The highest voltage for transmitting electrical power in India is

A)33 kV.
B)66 kV
C)132 kV
D)400 kV