|
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 |
|
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 drytype transformer because it reduces dissipation of heat |
|
31
|
The transformation ratio
of a transformer, for a given application is fixed but not constant |
|
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 |
|
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 |
