1
GATE EE 2004
MCQ (Single Correct Answer)
+2
-0.6
A 500 kVA, 3-phase transformer has iron loses of 300 W and full load copper losses of 600 W. The percentage load at which the transformer is expected to have maximum efficiency is
A
50.0%
B
70.7%
C
141.4%
D
200.0%
2
GATE EE 2004
MCQ (Single Correct Answer)
+2
-0.6
The resistance and reactance of a 100 kVA 11000|400 V, $$\triangle$$ - Y distribution transformer are 0.02 and 0.07 pu respectively. The phase impedance of the transformer referred to the primary is
A
(0.02 + j0.07) Ω
B
(0.55 + j1.925) Ω
C
(15.125 + j52.94) Ω
D
(72.6 + j254.1) Ω
3
GATE EE 2003
MCQ (Single Correct Answer)
+2
-0.6
Figure shows an ideal three-winding transformer. The three windings 1,2,3 of the transformer are wound on the same core as shown. The turn's ratio N1:N2:N3 is 4:2:1. A resistor of 10 Ω is connected across winding-2. A capacitor of reactance 2.5 Ω is connected across winding-3. Winding-1 is connected across a 400 V, ac supply. If the supply voltage phasor $$\overline V=400\angle0^\circ$$, the supply current phasor $${\overline I}_1$$ is given by GATE EE 2003 Electrical Machines - Transformers Question 53 English
A
(-10 + j10) A
B
(-10 - j10) A
C
(10 + j10) A
D
(10 - j10) A
4
GATE EE 2003
MCQ (Single Correct Answer)
+2
-0.6
Figure shows a $$\triangle$$ - Y connected 3-phase distribution transformer used to step down the voltage from 11000 V to 415 V line-to line. It has two switches S1 and S2. Under normal conditions S1 is closed and S2 is open. Under certain special conditions S1 is open and S2 is closed. In such a case the magnitude of the voltage across the LV terminals a and c is GATE EE 2003 Electrical Machines - Transformers Question 52 English
A
240 V
B
480 V
C
415 V
D
0 V
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