|
1
|
In a transformer minimum voltage regulation
occurs when the power factor of the load is leading |
|
2
|
Current transformers for meters and relays
usually have 5-A secondaries |
|
3
|
Increase in secondary current of a transformer
brings about increase in primary current. This is possible because primary and secondary windings are inductively coupled |
|
4
|
The output current corresponding to the maximum
efficiency for a transformer having core loss of 200 W and equivalent resistance referred to secondary of 0.5 ohm is 20 A |
|
5
|
Burden of a current transformer is usually
expressed in volt amperes |
|
6
|
The yoke sections of transformers using
hot-rolled laminations is made 15 per cent greater than that of the core so as to to reduce the iron loss in yoke and magnetizing current |
|
7
|
The humming sound in a transformer is mainly due
to magnetostriction |
|
8
|
Spiral core transformer which has core made up of
steel strip has the following advantage. Less weight,lighter construction,minimum losses |
|
9
|
Which value of flux is involved in the e.m.f.
equation of the transformer ? Maximum value |
|
10
|
Which of the following insulating materials is
used in power transformers ? Tapes of glass,press board,synthetic resin bonded paper. |
|
11
|
In some transformers, the tapping are provided
on H.V. side |
|
12
|
Minimum voltage regulation occurs when the power
factor of the load is leading |
|
13
|
The hum in a transformer is mainly attributed to
magnetostriction |
|
14
|
Which of the following protection is normally not
provided on small distribution transformers ? Buchholz relay |
|
15
|
In a power or distribution transformer about 10
per cent end turns are heavily insulated to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns |
|
16
|
Natural air cooling is generally restricted for
transformers up to 1.5 MVA |
|
17
|
Which type of winding is used in 3- phase
shell-type transformer ? Sandwich type |
|
18
|
An ideal transformer is one which has
no losses and magnetic leakage |
|
19
|
The full-load copper loss of a transformer is
1600 W. At half-load, the copper loss will be 400 W |
|
20
|
Which of the following properties is not
necessarily desirable for the material for transformer core ? High thermal conductivity |
