Question

(a) Explain what would happen if the gate is made positive with respect to the cathode during reverse blocking of a thyristor (no diagram required) [15%] (b) Draw a well labelled plot showing the variation of the anode voltage versus anode current of a thyristor (no graph paper, explanation or circuit diagram needed) [20 %] (c) Consider the circuit diagram shown below. Here V is the DC source voltage and the initial charge of the capacitor C is q(0)-0 . The time constant for the RC circuit is τ-RC. i(t) V, (i)If the switch S is closed at t -0, obtain the mathematical expressions for the current i(t) and voltage v (t) across the capacitor [3596] (ii)Find the initial rate of change of the capacitor voltage [10%] (iii) Sketch the time variation of current i(t) and voltage across capacitor v (t) . Label the plots clearly and mark the time constant in the plot for v (t) [20%]

Answer 1

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