Punjab Engineering College 2005 B.Tech Industrial Electronics - Question Paper

EC 303 B Tech fifth Sem
INDUSTRIAL ELECTRONICS
Note: part A is compulsory. Attempt any 4 ques. from part B and any 2 ques. from part C. presume any data if not provided.

part A Marks two every
1.

(a) elaborate the main differences ranging from p-n junction diodes and Schotty diodes?
(b) What is an off-state condition of thyristors?
(c) What would be the ripple frequency in six-phase full wave rectifier.
(d)Why is it necessary to remove harmonics from output of an inverter?
(e) What is cycloconverter?
(f) Enumerate industrial applications of cycloconverter.
(g) explain advantages and disadvantages of a multiphase chopper.
(h) How is chopper useful for controlling the speed of D.C. devices?
(i) discuss 2 factors on which the load voltage of a D.C. chopper circuit depends.
(j) What is basic principle of a switched mode power supply?



part B (Marks five each)
2. Draw and discuss the connection of a 3 phase full half controlled rectifier bridge.

3. discuss with the help of a diagram working principle of McMurray Bedford inverter circuit.

4. A series inverter circuit has an inductor of 10 mH, a capacitor of 47 mF connected in series with load resistance of five ohm. Determine the resonant frequency and time period of oscillations.
A single phase full converter is used to control the speed of a 7.5 kW, 220 V, 1800 rpm separately excited D.C. motor. The armature resistance is 0.25 ohm and the rated armature current is 20 A. The ac voltage is 250 V. The motor voltage constant is Kaf = 0.278 v/radian/min. For a firing angle a = 30o and rated motor current, determine:

(a) The speed of the motor
(b) Motor torque.

presume continuous and ripple free armature current.

6. explain the principle of stator voltage control of induction motor and how it is achieved.

part C (Marks 10 each)

7. Draw the circuit diagram of Jones chopper. discuss its operation with particular emphasis on the commutation process.

8. Show that the fundamental rms value of per phase output voltage of low frequency for m pulse cycloconverter is provided by:

Express Vor in terms of voltage reduction factor.

9. Write short notes on ay 2 of the following:
(a) Power MOSFETs
(b) Commutator less d.c. motor
(c) Switched mode power supplies.

Earning:   Approval pending.