Download JNTU (OR) M.TECH 1-Semester SOLID STATE POWER CONVERTERS January / February-2007 Exam Question Paper

Code No: OR-12/PWE
M.Tech. I-Semester Examinations, January/February-2007.
(Power Electronics)
Time: 3 hours                       Max. Marks: 60
Answer any FIVE questions
All questions carry equal marks

– – –
1.a)  Discuss the operation of 1-φ A.C voltage controller with R-L load.
b)  Discuss the operation when α ≤ φ.
c)  Explain the operation of synchronous top changer.

2.a)  What is the purpose of freewheeling diode?
b)  Why the power factor of a converter circuit is poor?
c)  Discuss the operation of 1-φ full converter with RLE type load.

3.a)  Discuss the non circulating mode of operation of dual converter.
b)  Draw the output voltage waveform of 3-φ halfwave converter with R-load and α = 90o.
c)  Derive the average voltage expression.

4.a)  Draw the circuit of a 3-φ cycloconverter and explain the operation of it.
b)  The input voltage to the cycloconverter is 220V, 50Hz.  The load resistance is 50Ω  and  the  load  inductance L = 40nH.  The frequency of the output voltage is 20Hz.  If the converter are operated as full converter such that   0 ≤ α ≤ Π and delay angle is     α = 120o.  Determine (i) rms value of output voltage  (ii) rms current of each thyristor (iii) input power factor.

5.  Discuss the operation of modified McMurray Bed ford inverter with
necessary waveforms.

6.a)  Discuss the operation of Autosequential current source inverter.
b)  Mention the merits and demerits of VSI and CSI.

7.a)  Discuss the operation of Jone’s Chopper.
b)  A separately excited dc motor has a rated speed of 800rpm, rated current
of 20A and Ra = 0.5ohm.  The supply voltage is 240V dc.  It is desired to
control the speed using a dc chopper.  (i) Find the duty cycle of chopper so
that motor may operate at 600rpm and develop the rated torque.  (ii) Find
the duty cycle if the motor operator at 600rpm and develops half the rated

8.  Discuss briefly series and parallel resonant converters.


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