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06000EE305 122002

PART ‏تا‎

Answer any two full questions, each carries 10 marks.
Explain the problems associated with the series operation of SCRs and the
method to solve the issues.
Explain the structure and operation of enhancement type MOSFET.
Sketch the variation of voltage across thyristor and current through it during the
turn-on process. Indicate the turn on time subdivisions and explain the nature of
these curves
A single-phase semi-converter delivers power to RLE load with R = 5 Q, L=
10 mH and E = 80 V. The ac source voltage is 230 V, 50 Hz. For a continuous
conduction, find the average value of output current for a firing angle delay of
50°. Sketch the input current and output voltage waveforms.
Describe the working of a single phase full-converter in the inverter mode with
RLE load. Draw the circuit diagram and illustrate your answer with waveforms
for load voltage and current, source current, current through and voltage across
one SCR. Assume constant load current. Obtain the expression for average
output voltage

PART C

Answer any two full questions, each carries 10 marks.
With circuit diagram and waveforms, explain six pulse and three pulse
operating modes of 3-phase semiconverter. Assuming continuous conduction of
load current, show that average output voltage is the same for both the
operating modes.
A 3-phase full converter is used for charging a battery with an emf of 110 V
and an internal resistance of 0.2 Q. For a constant charging current of 10 A,
compute the firing angle delay for ac line voltage of 220 V. Find also the
supply power factor.
Draw the circuit diagram for 3-phase voltage source inverter with star
connected resistive load on the assumption that each IGBT conducts for 120°.
Also draw the waveforms for current through any one IGBT, phase voltages
and line voltages.

A star connected load of 15 Q / phase is fed from 42017 ‏عل‎ source through a 3-

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