EE Conventional PaperII

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1.(A) Choose and write the correct answer from among the four options given in each case for (a)
to (j) below:
(a) Improved commutation in d.c machines cannot be achieved by
(i) Use of interpoles
(ii) Using brushes of higher resistivity
(iii) Increasing reactance voltage
(iv) Decreasing reactance voltage
(b) A two winding single phase transformer when connected either as a step down or step up
autotransformer, under the assumptions of ignoring core loss, copper loss, magnetizing
current and leakage reactance, will have the maximum VA rating for the autotransformed for
a given VA rating of the two winding transformer having N1 and N2 primary and secondary
turns respectively for
(i)
N / N 1.0 1 2
(ii)
N / N 1.0 1 2
(iii) N / N 1.0but 1.0 1 2
(iv)
N / N 1.0 1 2
© A surge of 10kV travels along a cable towards its junction with an overhead line. The surge
impedances of the cable and the line are
50
and
450
, respectively. The surge voltage
transmitted into the line is
(i) 18.0 kV (ii) 4.0 kV (iii) 20.0 kV (iv) 2.0 kV
(d)
The one line diagram of a simple power system is given above. The transformation ratio of
the stepup transformer is 11/220 kV. The base MVA = 100 and base kV = 11 on the
generator side. The base kV on the transmission side is
(i) 11 kV (ii) 220 kV (iii)
220 kV
3
(iv)
3 220kV
(e) An ideal currentcontrolled voltage source has the input resistance and the output resistance,
respectively.
(i)
,
(ii)
0,
(iii)
0, 0
(iv)
, 0 

