No. of Pages: 2 D
AP) ABDUL KALAM TECHNOLOGICAL UNIVERSITY

FIRST SEMESTER M.TECH DEGREE EXAMINATION, JUNE/JULY 2018
Branch: Electrical & Electronics Engineering

Stream(s): Control System, Electrical Machines

OIEE6303 POWER ELECTRONIC CIRCUITS

Answer any twofull questions from each part

Limit answers to the required points.

Max. Marks: 60 Duration: 3 hours
PARTA
1. a, Explain the tum-off process an IGBT with the help of appropriate voltage (4 Vand current waveforms.

b. Draw and explain voltage, current and power wave form of a practical switch. (5)

2. a. Assume linear variation with respect to time for both voltage and current, both (5)
during turn-on and turn-off The OFF-state voltage is V and ON-state current is I. The
switching frequency is f. Assume that the switch is ideal as regards its static
performance. Obtain expression for

(1) The average switching power loss
(11) 2 Instantaneous peak power loss in the switch
b. Explain with relevant diagrams and waveforms the operation of two stage (4 )sequence
control of a single phase a.c voltage contoller with RL load.
3. 8. Explain with circuit diagram and waveforms the working of a single- phase (5)
a.c voltage controller with resistive load.

b. Realize current bidirectional and voltage bidirectional two quadrant switches (4) and
explain its operation.

PART B
4. a. Explain the operation of buck converter with the help of circuit diagram and (5) relevant
waveforms.

b. A boost regulator has an input voltage Vs = 6 V.The average output voltage Va (4) =
15۷ and the average load current la = 0.5A. The switching frequency is 20 kHz. If L
= 250 uH and C=440 gF determine (i) Duty cycle K; (ii) The ripple current of
inductor Al ; (iii) The peak current of inductor and (iv) The ripple voltage of filter
capacitor AVC. The switching frequency is 25 kHz.

5. a. Describe with relevant diagrams and waveforms the working of a forward (4 converter.

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