GTU Power Electronics And Industrial Drives - December 2014 Exam Question Paper

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GTU Electrical and Electronic Engineering (Semester 7)
Power Electronics And Industrial Drives
December 2014

Total marks: --
Total time: --

INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Explain about the construction, characteristics and gate drive requirements of SCR.

7 M

1 (b) With neat sketch describe the operation of half wave uncontrolled rectifier with R-L load.

7 M

2 (a) The three phase full wave rectifier has a load of L=1.5 MHz, R=2.5Ω and E=10 V. 07 The input voltage is Vin =208V,60 Hz. Determine
1. The steady state load current Io at ω=π/3t
2. The average diode current Io
3. The RMS diode current Ir
4. The RMS output current Irms.

7 M

Answer any two question from Q2 (b) or Q2 (c)

2 (b) Explain Turn-off mechanism in Thyristor. Explain commutation methods of Thyristors briefly.

7 M

2 (c) What is VSI? Describe the operation of single phase half bridge VSI. Also state the switching state table for the same.

7 M

Answer any two question from Q3 (a), (b) or Q3 (c), (d)

3 (a) Explain the following PWM methods for control of single phase inverter
Single pulse width modulation.
Sinusoidal pulse width modulation.

7 M

3 (b) Briefly discuss the 120 degree operation of inverter circuit with appropriate waveforms.

7 M

3 (c) Discuss the class B operation of Chopper Circuit.

7 M

3 (d) What is DC drive? Discuss basic characteristics of DC motors.

7 M

Answer any two question from Q4 (a), (b) or Q4 (c), (d)

4 (a) Discuss the role of snubber circuit from protection aspect.

7 M

4 (b) A single phase half wave AC voltage controller has a resistive load of 10 + and the input voltage is 120 V, 60 Hz. The delay angle of thyristor is 90°. Determine (a) RMS value of the output voltage (b) the input Power Factor (c) the average input current.

7 M

4 (c) Discuss about choice of AC and DC drive in detail.

7 M

4 (d) Discuss operation of 3-phase ac to ac converter with star connected resistive load.

7 M

Answer any two question from Q5 (a), (b) or Q5 (c), (d)

5 (a) Briefly discuss the operation of current source inverter with necessary waveform.

7 M

5 (b) Briefly discuss the operation of single phase semi converter d.c. drives.

7 M

5 (c) Explain three phase cyclo-converter and sinusoidal harmonic reduction techniques for cycloconverter.

7 M

5 (d) Classify synchronous motor drives. Explain brushless DC and AC motor.

7 M

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