1
GATE EE 2014 Set 1
MCQ (Single Correct Answer)
+2
-0.6
The core loss of a single phase, 230/115 V, 50 Hz power transformer is measured from 230 V side by feeding the primary (230 V side) from a variable voltage variable frequency source while keeping the secondary open circuited. The core loss is measured to be 1050 W for 230 V, 50 Hz input. The core loss is again measured to be 500W for 138 V, 30 Hz input. The hysteresis and eddy current losses of the transformer for 230 V, 50 Hz input are respectively.
A
508 W and 542 W
B
468 W and 582 W
C
498 W and 552 W
D
488 W and 562 W
2
GATE EE 2014 Set 3
MCQ (Single Correct Answer)
+2
-0.6
The parameters measured for a 220V/110V, 50 Hz, single-phase transformer are:

Self inductance of primary winding = 45 mH
Self inductance of secondary winding = 30 mH
Mutual inductance between primary and secondary windings = 20 mH

Using the above parameters, the leakage (Ll1 , Ll2) and magnetizing (Lm) inductances as referred to primary side in the equivalent circuit respectively, are
A
5mH, 20mH and 40mH
B
5mH, 80mH and 40mH
C
25mH, 10mH and 20mH
D
45mH, 30mH and 20mH
3
GATE EE 2014 Set 3
MCQ (Single Correct Answer)
+2
-0.6
The mean thickness and variance of silicon steel laminations are 0.2 mm and 0.02 respectively. The varnish insulation is applied on both the sides of the laminations. The mean thickness of one side insulation and its variance are 0.1 mm and 0.01 respectively. If the transformer core is made using 100 such varnish coated laminations, the mean thickness and variance of the core respectively are
A
30 mm and 0.22
B
30 mm and 2.44
C
40 mm and 2.44
D
40 mm and 0.24
4
GATE EE 2014 Set 3
MCQ (Single Correct Answer)
+2
-0.6
An open circuit test is performed on 50 Hz transformer, using variable frequency source and keeping V/f ratio constant, to separate its eddy current and hysteresis losses. The variation of core loss/frequency as function of frequency is shown in the figure GATE EE 2014 Set 3 Electrical Machines - Transformers Question 61 English The hysteresis and eddy current losses of the transformer at 25 Hz respectively are
A
250 W and 2.5 W
B
250 W and 62.5 W
C
312.5 W and 62.5 W
D
312.5 W and 250 W
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