Electrical Machine - IES Academy
Electrical Machine - IES Academy
Electrical Machine - IES Academy
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India’s No. 1<br />
<strong>IES</strong> <strong>Academy</strong><br />
Transformer<br />
Chapter-1<br />
I<strong>IES</strong>-14. When are eddy-current losses in a transformer reduced [<strong>IES</strong>-2008]<br />
(a) If laminations are thick<br />
(b) If the number of turns in primary winding is reduced<br />
(c) If the number of turns in secondary winding is reduced<br />
(d) If laminations are thin<br />
Auto - Transformer<br />
<strong>IES</strong>-15.<br />
In case of auto-transformers, which of the following statements are<br />
correct<br />
[<strong>IES</strong>-2001]<br />
1. An auto-transformer requires less copper as compared to a<br />
conventional, 2-winding transformer of the same capacity.<br />
2. An auto-transformer provides isolation between the primary and<br />
secondary windings<br />
3. An auto-transformer has less leakage reactance as compared to the<br />
conventional, 2-winding transformer of the same capacity.<br />
Select the correct answer using the codes given below:<br />
(a) 1, 2 and 3 (b) 1 and 2 (c) 1 and 3 (d) 2 and 3<br />
<strong>IES</strong>-16.<br />
<strong>IES</strong>-17.<br />
A two-winding transformer is used as an autotransformer. The kVA<br />
rating of the autotransformer compared to the two-winding transformer<br />
will be:<br />
[<strong>IES</strong>-2002]<br />
(a) 3 times (b) 2 times (c) 1.5 times (d) Same<br />
A two-winding transformer is converted into an auto-transformer. If we<br />
apply additive polarity and subtractive polarity for the connections, then<br />
the secondary voltage is 2640 V and 2160 V, respectively. What is the ratio<br />
of primary to secondary voltage of the original transformer [<strong>IES</strong>-2006]<br />
(a) 66 : 54 (b) 54 : 66 (c) 10 : 1 (d) 1 : 10<br />
<strong>IES</strong>-18. A single-phase, 10kVA, 2000/<br />
200V, 50Hz transformer is<br />
connected to form an auto<br />
transformer as shown in the<br />
figure given below. What are<br />
the values of V 1<br />
and I 2<br />
,<br />
respectively<br />
[<strong>IES</strong>-2005]<br />
(a) 2200V, 55A (b) 2200V, 45A (c) 2000V, 45A (d) 1800V, 45A<br />
<strong>IES</strong>-19.<br />
If the wave form of the voltage impressed on the primary of a Y −Δ bank<br />
contains 5 th harmonics, what are the wave forms of the resultant voltages<br />
of the primary and the secondary<br />
[<strong>IES</strong>-2005]<br />
Primary<br />
Secondary<br />
(a) Peaked<br />
Peaked<br />
(b) Peaked<br />
Flat-topped<br />
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