Deemed University 2009 A.M.I.E.T.E Electronics

(C) high duty cycle. (D) square wave.


h. In a Single pulse width modulation technique the dominant harmonic is:


(A) 3rd. (B) 5th.
(C) 11th. (D) 2nd.

i. 3 phase to 3 phase cycloconverter provide better output as compared to single phase to single phase cycloconverter.


(A) actual (B) False

j. The main difference ranging from thyristor and PUT is that


(A) The gate of PUT is connected in n-type material near cathode.
(B) The gate of PUT is connected in n-type material near anode.
(C) PUT has no gate.
(D) PUT is used for firing of thyristor.


ans any 5 ques. out of 8 ques..
every ques. carries 16 marks.

Q.2 a. discuss the methods of turning on and turning off the thyristor. (8)

b. Write short notes on:-
(i) Cooling of thyristor.
(ii) Power MOSFET. (8)

Q.3 a. discuss Extinction angle control for the power factor improvement for 3 phase dual converter. (8)

b. explain effect of impedance on
(i) Single phase
(ii) 3 phase converter operation. (8)

Q.4 a. Classify and compare various kinds of switched mode regulators. (10)

b. A step up chopper has supply voltage of 250 V while the output voltage is 500 V. If the off period of chopper be 100 msec, determine the pulse width of the output voltage. (6)

Q.5 a. What is the difference ranging from forced and natural commutation? define an impulse commutation circuit. (10)

b. explain di/dt and dv/dt feature of a thyristor. (6)

Q.6 a. List and draw the different configurations of 3 phase ac voltage regulators. (8)

b. explain the operation of a single phase ac voltage controller for an inductive load. (8)



Q.7 a. elaborate cycloconverters? discuss single phase to single phase cycloconverter with relevant diagrams. (8)

b. Write short notes on:-
(i) Reduction of harmonics in output.
(ii) Circulating current mode operation of cycloconverter. (8)

Q.8 a. State and discuss various methods of voltage control in single phase inverters. (8)

b. A three phase bridge inverter is fed from a 400 V battery. The load is star connected and has a resistance of 10 ohms per phase. obtain the rms load current, power output, peak current of thyristor. presume 180o mode of operation. (8)

Q.9 a. Draw and discuss in brief the circuits for single phase and 3 phase converter drives. (8)

b. A 230V, 1500 rpm separately excited dc motor has an armature resistance of 1O and rated armature current of 10 A. It is fed from 230 V single phase AC, 50 Hz through a fully controlled bridge converter. calculate speed if torque is five N-m and firing angle is 30o. (8)

Earning:   Approval pending.