In the chopper circuit shown in fig the input $$dc$$ voltage has a constant value $${{V_s}}$$. the output voltage $${{V_0}}$$ is assumed ripple free. The switch $$S$$ is operated with a switching time period $$T$$ and a duty ratio $$D.$$ What is the value of $$D$$ at the boundary of continuous and discontinuous conduction of the inductor current $${i_L}$$?

A step down chopper is operated in the continuous conduction mode in steady state with a constant duty ratio $$D.$$ If $${V_0}$$ is the magnitude of the $$dc$$ output voltage and if $${V_s}$$ is the magnitude of the $$dc$$ input voltage, the ratio $${{{V_0}} \over {{V_s}}}$$ is given by

In the single phase diode bridge rectifier shown in fig, the load resistor is
$$R = 50\Omega .$$ The source voltage is
$$V = 200sin\omega t,$$
Where $$\omega = 2\pi \times 50$$ radians per second. The power dissipated in the load resistor $$R$$ is

A three phase thyristor bridge rectifier is used in a $$HVDC$$ link. The firing angle $$\alpha $$ (as measured from the point of natural commutation) is constrained to lie between $${5^ \circ }$$ and $${30^ \circ }$$. If the $$dc$$ side current and $$ac$$ side voltage magnitude are constant, which of the following statements is true (neglect harmonics in the $$ac$$ side current and commutation overlap in your analysis)