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Q 1/53
Score 0
A transformer core is laminated to
30
reduce all above losses
reduce eddy current losses
reduce hysteresis loss
reduce copper loss
Q 2/53
Score 0
The efficiency of a transformer will be maximum when
30
copper losses = iron losses
copper losses = hysteresis losses
hysteresis losses = eddy current losses
eddy current losses = copper losses
53 questions
Q.
A transformer core is laminated to
1
30 sec
Q.
The efficiency of a transformer will be maximum when
2
30 sec
Q.
A transformer transforms
3
30 sec
Q.
Two transformers operating in parallel will share the load depending upon their
4
30 sec
Q.
The path of the magnetic flux in transforme should have
5
30 sec
Q.
The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be
6
30 sec
Q.
Which winding of the transformer has less cross-sectional area
7
30 sec
Q.
Open circuit test on transformer is conducted to determine
8
30 sec
Q.
Short circuit test on transformer is conducted to determine
9
30 sec
Q.
The hum in a transformer is mainly attributed to
10
30 sec
Q.
A transformer is working at its maximum efficiency. Its iron loss is 1 kW. Its copper loss will be
11
30 sec
Q.
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
12
30 sec
Q.
The working principle of a transformer is
13
30 sec
Q.
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 ohms is
14
30 sec
Q.
For parallel operation of two single phase transformers the essential condition is that they should have the same
15
30 sec
Q.
Transformer is used to change the values of
16
30 sec
Q.
Electric power is transferred from one coil to the other coil in a transformer
17
30 sec
Q.
At every instant the direction of secondary current in a transformer must be such as to oppose any change in flux. This in accordance with
18
30 sec
Q.
If in a transformer the secondary turns are doubled and at the same time the primary voltage is reduced by half, then the secondary voltage will
19
30 sec
Q.
Which is the common method of cooling a power transformer?
20
30 sec
Q.
The transformer oil used in transformers provides
21
30 sec
Q.
Three number of 10:1 transformers are connected in Y-Delta to supply a load at 230 V. The supply voltage of this transformer must be
22
30 sec
Q.
A transformer has a turns ratio of 1 to 10 and a resistance of 5000 ohms is connected across the secondary terminals, the resistance offered to a current flowing in the primary will be
23
30 sec
Q.
Three units of 1.5 transformers are connected in Delta-Wye to supply a 3-phase load from a 400 V, 3-phase source. The line voltage on the load side is
24
30 sec
Q.
A transformer is working at its full load and its efficiency is also maximum. Its iron loss is 1000 W, its copper loss at half load will be
25
30 sec
Q.
In power transformers the tappings are provided on
26
30 sec
Q.
Three single-phase transformer, each with a 10 KVA rating are connected in a closed delta arrangement. If one transformer is taken out capacity of the system will be
27
30 sec
Q.
When 440/220 V transformer is connected to 400 V d.c supply
28
30 sec
Q.
A transformer has a core loss of 64 W and copper loss of 144 W, when it is carrying 20% overload current. The load at which this transformer will operate at the maximum efficiency is
29
30 sec
Q.
If 500-kVA, 400 Hz transformer is operated at 100 Hz, its kVA rating is
30
30 sec
Q.
The efficiency in transformer is maximum at
31
30 sec
Q.
For 100% efficient transformer if the number of turns in the primary and secondary are 1000 and 100 respectively and the input to the transformer is 1000 W, the power output will be
32
30 sec
Q.
No-load test on a transformer is carried out to determine
33
30 sec
Q.
The main purpose of performing open-circuit test at rated voltage is to measure
34
30 sec
Q.
The short-circuit test in a transformer is use to determine
35
30 sec
Q.
When a 400-Hz transformer is operated at 50-Hz, its kVA rating is
36
30 sec
Q.
The iron-losses of a transformer can be calculated by knowing the weights of
37
30 sec
Q.
The output current corresponding to the maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to secondary of 0.25 ohms is
38
30 sec
Q.
If a current transformer has a ratio of 100:5 and an ammeter connected to its secondary reads 2.5 A, the actual line current is
39
30 sec
Q.
For supplying a balanced 3-phase load of 40-kVA rating of each transformer in V-V bank should be
40
30 sec
Q.
The percentage over-loading of two 20-kVA transformers when supplying a balanced 3-phase load of 40kVA in V-V bank is
41
30 sec
Q.
For small power transformers, it is preferable to use
42
30 sec
Q.
For large power transformers, it is preferable to use
43
30 sec
Q.
Eddy current loss in a tranformer depends on
44
30 sec
Q.
The short-circuit test on a transformer is conducted to obtain
45
30 sec
Q.
Transformer -core laminations are made of
46
30 sec
Q.
The essential condition for parallel operation of two single-phase transformers is that they should have same
47
30 sec
Q.
Part of the transformer which is most subject to damage from overheating is
48
30 sec
Q.
In general, the most important point to keep under constant watch during the operation of a transformers is its
49
30 sec
Q.
In a 10: 1 step-down 2200/220-V transformers, taps are changed to reduce the number of primary turn by 5%. The secondary voltage will nearly be
50
30 sec
Q.
The color of fresh dielectric oil for a transformer is
51
30 sec
Q.
A 10 kVA, 230/1000V single transformer is fed from a 230 V supply. The voltage across the load will be
52
30 sec
Q.
A 5 kVA 200/100 V single phase transformer delivers 50 A at rated voltage. The input current will be