| POWER ELECTRONICS |
| PAPER NO. 4 |
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EC POWER ELECTRONICS (B.Tech 4th Semester,2052) Time : 3 Hours Maximum Marks : 60 NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C Section-A Marks : 20 1(a) Explain the difference between Latching and holding current. (b) Draw two transistor analogy of SCR. (c) Calculate r.m.s. value for half-wave rectifier sine wave. (d) List the names of various triggering methods of SCR. (e) What are causes of instability in a.c. motors? (f) Draw the T-N characteristics of a d.c. motor and label it. (g) Draw a snubber circuit and explain its applications. (h) Draw the circuit symbols of SCR, DIAC, TRIAC, UJT, LASCR. (i) Explain with the help of waveforms the effect of inductive load on the performance of a half-wave rectifier using one thyristor (j) What is the purpose of free wheeling diode ? Explain. Section-B Marks:5 Each 2. Draw and label the characteristics of UJT, how it can be used as relaxation oscillator ? 3. Why is it necessary to remove harmonics from the O/P of an inverter and how can they be elimiated ? 4. Draw the basic block diagram of D.C> voltage regulators, and what do you understand by Regylation ? 5. What are the various applications of cycloconverters ? Explain the working of step up cycloconverter. 6. A dielectric heater is used to heat a non-metal piece having dimensions 10 x 5 x 2 cm from a temperature of 25o C to 100o C in 5 minutes. The specic heat = 1500 J/kg/oC, density of material = 200 kg/m3, dielectric constt, = 5, power factor = 0.06. Find the power required for heating. Section-C Marks : 10 Each 7. Explain various types of communication circuits with suitable diagrams. 8. (a) What is skin effect and how is it useful for induction Heating ? (b) A copper conductor has a circular cross-section 5 c 9. Write short notes on any two of the file following : (a) Three phase rectifiers (b) Dual converters (c) Delay Timers. |
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