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Transformer
Chapter-1
(a) 240 V (b) 480 V (c) 4'15 V (d) 0 V
GATE-11. Which three-phase connection can be used in a transformer to introduce
a phase difference of 30° between its output and corresponding input
line voltages
[GATE-2005]
(a) Star-Star (b) Star-Delta (c) Delta-Delta (d) Delta-Zigzag
GATE-12. Three single-phase transformers
are connected to
form a 3-phase transformer
bank. The transformers are
connected in the following
manner:
The transformer connection will be represented by: [GATE-2008]
(a) Yd0 (b) Yd 1 (c) Yd6 (d) Yd l1
Common Data for Questions Q13 and Q14:
The star-delta transformer shown above
is excited on the star side with balanced,
4-wire, 3-phase, sinusoidal voltage
supply of rated magnitude. The
transformer is under no load condition.
GATE-13. With both S1 and S2 open, the core flux waveform will be: [GATE-2009]
(a) A sinusoid at fundamental frequency (b) Flat –topped with harmonic
(c) Peaky with third-harmonic
(d) None of these
GATE-14. With S2 closed and S1 open, the current waveform in the delta winding
will be:
[GATE-2009]
(a) A sinusoid at fundamental frequency
(b) Flat-topped with third harmonic
(c) Only third-harmonic
(d) None of these
Auto - Transformers
GATE-15. A 50 kVA, 33001230 V single-phase
transformer is connected as an
autotransformer shown in figure.
The nominal rating of the
autotransformer will be:
(a) 50.0 kVA (b) 53.3 kVA
(c) 717.4 kVA (d) 767,4 kVA [GATE-2004]
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