GATE 2023 EE – Question 58
The single phase rectifier consisting of three thyristors $T_1$, $T_2$, $T_3$ and a diode $D_1$ feed power to a 10 A constant current load. $T_1$ and $T_3$ are fired at $\alpha=60^\circ$ and $T_2$ is fired at $\alpha=240^\circ$. The reference for $\alpha$ is the positive zero crossing of $V_{in}$. The average voltage $V_O$ across the load in volts is _____ (Round off to 2 decimal places).
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Correct answer: 47.51 to 47.99
Explanation
During the positive half-cycle $T_1$ and $T_3$ conduct from $60^\circ$ to $180^\circ$ and the output equals $V_{in}$. From $180^\circ$ to $240^\circ$ the load current freewheels and the output is zero. In the negative half-cycle $T_2$ and $D_1$ conduct from $240^\circ$ to $360^\circ$, with output $-V_{in}$. $V_o=\dfrac{100}{2\pi}\left[\int_{60^\circ}^{180^\circ}\sin\theta\,d\theta+\int_{240^\circ}^{360^\circ}(-\sin\theta)\,d\theta\right]=\dfrac{100}{2\pi}(1.5+1.5)=47.75$ V.