EE SHORT NOTES TRANSFORMERS PART 2

21

Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds
150°C

22

The noise resulting from vibrations of laminations set by magnetic forces, is termed as
hum

23

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
R2/K2

24

Power transformers are designed to have maximum efficiency at
nearly full load

25

Primary winding of a transformer
could either be a low voltage or high voltage winding

EE SHORT NOTES TRANSFORMERS PART 2

26

The permissible flux density in case of cold rolled grain oriented steel is around
1.7 Wb/m2

27

Which of the following does not change in a transformer ?
Frequency

28

In a transformer maximum voltage regulation occurs when the power factor of the load is
lagging

29

Which of the following statement concerning parallel operation of transformers is incorrect ?
Transformers must have equal kVA

30

Dust should never be allowed to accumulate on the windings and core of a dry type transformer because it
reduces dissipation of heat

31

The transformation ratio of a transformer, for a given application
is fixed but not constant

EE SHORT NOTES TRANSFORMERS PART 2

32

Which of the following can be reduced when the flux density in the transformer core is increased ?
Size of the transformer

33

Buchholz relay is used in
transformer protection

34

In core-type transformers, the concentric windings are used with
low voltage winding placed next to core

35

A sinusoidal e.m.f.
lags the flux inducing it by 90°

36

A distribution  transformer has low flux density because
it is constantly connected to the supply

37

The kVA rating ratio of transformers operating in parallel, as a general rule, should be within
3 : 1

38

H.R.C. fuses on a transformer provide protection against
external faults

EE SHORT NOTES TRANSFORMERS PART 2

Category: New Jobs 

39

Which of the following: statements about a transformer having a small short-circuit voltage is true ?
A high short-circuit current flows through the transformer

40

A transformer is working at its full load and its efficiency is also maximum. Its iron loss is 1 kW, its copper loss at half load will be
0.25 kW