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GATE 2022 : Power Electronics Quiz 2

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Question 1

For a thyristor, maximum junction temperature is 115°C . The thermal resistance for the thyristor sink combination are θJC=0.20°C/W and θCS=0.16°C/W. The sink have temperature of C . Find the total average power loss in Thyristor sink combination?

Question 2

The latching current for a thyristor inserted between a dc source voltage of 80V and a load being 55mA. Calculate the minimum width of the gate-pulse required to turn-on the thruster when the load is
(i)Purely inductive having an inductance of 50 mH and
(ii) Consisting of resistance and inductance of 5 ohm and 50 mH respectively.

Question 3

A diode is used in an application carrying half sinusoidal current of period 2 msec and a peak of 50 A as shown in figure. Diode may model during conduction to have a constant voltage drop of 1.2 V and a dynamic resistance of 5 mΩ. Calculate the average conduction loss in the device?

Question 4

In a triggering circuit, source voltage is 16 volt and load line has a slope of -128 V/A. The triggering voltage and triggering current for an average gate power dissipation of 0.5 W is

Question 5

Four 600 V thyristors are connected in series to share a 2kV supply voltage. The maximum forward leakage current is 3mA, and the maximum difference in recovery charge is 15μC. The circuit arrangement for static and dynamic voltage sharing is that shown in Figure with R2 = 15Ω. A. Determine the values of R1 and C, and the maximum discharge current, assuming equal voltage sharing.

Question 6

The reverse recovery time for a power diode is 5 μsec. The rate of diode current delay is 30 A/μsec. If the softness factor value is 0.2 . The storage charge in the diode will be _________.
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