Power Electronics - Jun 2014

Electronics and Comm. Engg. (Semester 7)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) List the different members of the thyristor family and draw their characteristics and explain in brief.(7 marks) 1 (b) Explain single phase half wave rectifier with suitable circuit and waveform.(7 marks) 2 (a) Discuss briefly the parallel operation of MOSFETs.(7 marks) 2 (b) Explain the safe operating areas of an IGBT.(7 marks) 2 (c) A three-phase fully- controlled bridge converter is connected to three-phase a.c. supply of 400 V, 50Hz and operates with a firing angle α=π/4. The load current is maintained at 10A and the load voltage is 360 V. Compute: (i) Source inductance, L s (ii) Load resistance, R (iii) Overlap angle,μ(7 marks) 3 (a) Explain the various techniques of improving power factor in three phase controlled converters.(7 marks) 3 (b) Explain the DC Chopper's principal of operation .(7 marks) 3 (c) A DC Chopper operates on 230 V dc and frequency of 400Hz; feed an R-L load. Determine the ON time of the chopper for output of 150 V.(7 marks) 3 (d) Briefly discuss the switching behavior of a GTO.(7 marks) 4 (a) Explain single phase full bridge inverter.(7 marks) 4 (b) A single-phase half bridge inverter has a resistive load of R= 3Ω and the dc input voltage E_dc =24 Volts.
Determine: (i) IGBT ratings (ii) Total Harmonics distortion THD (iii) The distortion factor DF (iv) The Harmonics factor and DF of the lowest order Harmonic.(7 marks) 4 (c) Discuss the pulse width modulated inverter.(7 marks) 4 (d) Explain three phase bridge inverter.(7 marks) 5 (a) Explain the operation of UPS system.(7 marks) 5 (b) Explain switched mode power supplies.(7 marks) 5 (c) Compare dielectric heating with induction heating.(7 marks) 5 (d) Draw and explain the operation of automatic battery charger with trickle charging arrangement.(7 marks)