GATE EE 2016 Question Paper (06-Feb-2016) (Shift 2)

A $30MVA$, 3-phase, $50Hz,13.8kV$, star-connected synchronous generator has positive, negative and zero sequence reactances, $15\%,15\%and5\%$ respectively. A reactance ($X_n$) is connected between the neutral of the generator and ground. A double line to ground fault takes place involving phases ${}^{\prime }{b}^{\prime }and{}^{\prime }{c}^{\prime }$, with a fault impedance of $j0.1p.u.$ The value of $X_n$ (in $p.u.$) that will limit the positive sequence generator current to $4270A$ is _________.

If the star side of the star-delta transformer shown in the figure is excited by a negative sequence voltage, then

single-phase thyristor-bridge rectifier is fed from a $230V,50Hz$, single-phase AC mains. If it is delivering a constant DC current of $10A$, at firing angle of $30^o$, then value of the power factor at AC mains is

The switches $T1$ and $T2$ in Figure (a) are switched in a complementary fashion with sinusoidal pulse width modulation technique. The modulating voltage vm (t) = 0.8 sin $\left(200\pi t\right)V$ and the triangular carrier voltage $\left(V_c\right)$ are as shown in Figure (b). The carrier frequency is $5kHz$. The peak value of the $100Hz$ component of the load current $\left(i_L\right)$, in ampere, is ________

The voltage $\left(V_s\right)$ across and the current $\left(i_s\right)$ through a semiconductor switch during a turn ON transition are shown in figure. The energy dissipated during the turn – ON transition, in $mJ$, is_______.