Important RGPV Question
EC- 604 (C) Power Electronics
VI Sem, EC
UNIT 1-Power Semiconductor Switches
Q.1) Explain the transistor model of the Thyristor and derive the expression for anode current in terms of current gain.
(RGPV May 2024)
Q.2) Draw and explain the static and dynamic characteristics of a thyristor.
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Q.3) Explain the transistor model of the IGBT and draw its V-I characteristics.
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Q.4) What are the necessary conditions to turn off the thyristor? Discuss different techniques to commute the thyristor.
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Q.5) What do you understand by fast recovery diodes? With the help of diagram explain the static characteristics of power diodes.
(RGPV May 2023)
Q.6) Draw and explain the transfer characteristic of power MOSFET.
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Q.7) Describe with neat diagram the working of IGBT with its transfer characteristics.
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Q.8) Why does unequal voltage sharing take place among series connected thyristors during steady state and dynamic state? How is equal voltage sharing obtained in both the states?
(RGPV May 2023)
UNIT 2-Rectifiers and Line frequency phase controlled rectifiers using SCR
Q.1) Explain the operation of single-phase half controlled bridge rectifier for RL load and derive the expression for Ripple factor.
(RGPV May 2024)
Q.2) A single-phase half controlled bridge rectifier supplied from 220 V, 50 Hz AC source feeds a resistance load of 20Ω. Calculate the power dissipated in the load when the rectifier operates at a firing angle of 30°.
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Q.3) Draw the circuit diagram of three-phase, six-pulse controlled rectifier. Find out the average and rms values of voltage and current for resistive load.
(RGPV May 2024)
Q.4) Draw the static V-I characteristic of the SCR and explain its mode of operation.
(RGPV May 2023)
Q.5) What do you mean by Commutation? Explain in brief about External Pulse commutation.
(RGPV May 2023)
Q.6) Explain the effect of source inductance on the operation of single phase full bridge converter.
(RGPV May 2023)
Q.7) Find the number of thyristors each with a rating of 500 V and 75 A required for each branch of series and parallel combination for a circuit for a total voltage and current rating of 7.5 kV and I kA. Also compare the series and parallel string efficiency. Assume derating factor of 14%.
(RGPV May 2023)
Q.8) Explain the operation of a 1-Φ fully controlled bridge converter feeding a RL load. Also draw relevant output voltage and current waveforms.
(RGPV May 2023)
UNIT 3- Line frequency phase controlled rectifiers using SCR
Q.1) A single-phase full bridge inverter with an RL load of R = 20Ω and L = 10 mH, produces a square wave. It is fed from a 100 V de input. Find the rms load voltage, first fundamental rms and total harmonic distortion.
(RGPV May 2024)
Q.2) Explain the single-phase dual converter with proper circuit diagram and different waveforms.
(RGPV May 2024)
Q.3) A single-phase full bridge inverter has a pure resistive load of R = 20Ω and the output voltage is controlled by the multiple PWM technique. The width of each pulse is 28° and each half cycle has 4 pulses. The input voltage is 120V dc. Find the rms output voltage and the maximum possible input voltage if the maximum pulse width is 35°.
(RGPV May 2024)
Q.4) Draw the diagram of three-phase bridge inverter circuit and explain its working. What are the two modes of operation? How these modes are obtained?
(RGPV May 2024)
Q.5) Explain the different harmonic control techniques for an inverter.
(RGPV May 2023)
UNIT 4- AC Voltage Controllers
Q.1) What are the advantages of current-driven inverters over voltage-driven inverters? Describe the working of a single-phase current driven inverter.
(RGPV May 2024)
Q.2) What is cycloconverter? Enumerate some of its applications. Describe the three-phase to single-phase cycloconverter with the help of appropriate diagrams.
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Q.3) A three-phase cycloconverter supplies a single-phase load of 250V, 50 A. Find the input voltage and rms voltage for delay α = 0.
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Q.4) Describe the operation of 1-Φ full wave ac voltage controller with inductive load. Derive expression for output voltage.
(RGPV May 2023)
Q.5) A motor single phase voltage controller has input voltage of 230 Volts, 50 Hz and R= 15 ohms. For 6 cycles on and 4 cycles off, determine r.m.s output voltage and input power factor.
(RGPV May 2023)
UNIT 5-DC – DC Converters
Q.1) Draw and explain the circuit diagram of step-up chopper and drive an expression for output voltage in terms of duty ratio.
(RGPV May 2024)
Q.2) A chopper is operating at a frequency of 2 KHz on a 230 V de input supply. If the load voltage is 150 V, calculate the conduction and non-conduction period of the thyristor in each cycle.
(RGPV May 2024)
Q.3) Describe the working of step-up converter and derive the expression for output voltage.
(RGPV May 2023)
Q.4) Describe fly-back SMPS with relevant equivalent circuit and waveforms.
(RGPV May 2023)
EXTRA QUESTIONS-
Q.1) Describe the operation of a 1-Φ full bridge inverter. Draw wave shapes of output current when:
i) Load is pure resistive
ii) Load is pure inductive
(RGPV May 2023)
— Best of Luck for Exam —
