INDUSTRIAL ELECTRONICS EC 303 B Tech 5th Sem

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Note: Section A is compulsory. Attempt any Four questions from Section B and any Two questions from Section C. Assume any data if not given.
Section A Marks 2 each
1.
What are the main differences between p-n junction diodes and Schotty diodes?
What is an off-state condition of thyristors?
What would be the ripple frequency in six-phase full wave rectifier.
Why is it necessary to remove harmonics from output of an inverter?
What is cycloconverter?
Enumerate industrial applications of cycloconverter.
Discuss advantages and disadvantages of a multiphase chopper.
How is chopper useful for controlling the speed of D.C. devices?
Explain two factors on which the load voltage of a D.C. chopper circuit depends.
What is basic principle of a switched mode power supply?



Section B Marks 5 each
2. Draw and explain the connection of a three phase full half controlled rectifier bridge.

3. Explain 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 5 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:
The speed of the motor
Motor torque.

Assume continuous and ripple free armature current.

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

Section C Marks 10 each

7. Draw the circuit diagram of Jones chopper. Explain 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 given by:

Express Vor in terms of voltage reduction factor.


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

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