1 (a)
List the advantages of dc chopper drives over line commutated converter controlled dc drives.

5 M

1 (b)
Explain how semiconverter provides better power factor compared to full converter when both are working as rectifier with RL load.

5 M

1 (c)
What are advantages of flyback converter compared to forward converter?

5 M

1 (d)
Compare between current source and voltage source inverters.

5 M

2 (a)
Draw and explain the operation of speed control of a DC series motor fed by a single phase semiconverter for the continuous motor current. Draw also the associated voltage and current waveforms.

10 M

2 (b)
A 220 V, 1500 rpm, 10 A separately expired dc motor has an armature resistance of 1 ohm. It is fed from a single phase fully controlled bridge rectifier with an ac source voltage of 230, 50Hz. Assuming continuous load current compute:

i) Motor speed at firing angle of 30° and torque of 5 NM.

ii) Developed torque at firing angle of 45° and speed of 1000rpm.

i) Motor speed at firing angle of 30° and torque of 5 NM.

ii) Developed torque at firing angle of 45° and speed of 1000rpm.

10 M

3 (a)
Explain the operation of dual converter with circulating current. What are the advantages and disadvantages of the same?

10 M

3 (b)
With neat circuit diagram explain the working of load commulated chopper with relevant voltage and current waveforms. Show voltage variation across each pair of SCRs as a function of time.

10 M

4 (a)
Explain the working of McMurry bridge inverter using circuit diagram and appropriate waveforms.

10 M

4 (b)
Explain the operation of Induction Motor for two different cases when fed by current source inverter.

i) Operation at and below rated frequency

ii) Operation above rated frequency.

i) Operation at and below rated frequency

ii) Operation above rated frequency.

10 M

5 (a)
Discuss the stator voltage control scheme of induction motor, Also draw and explain the speed torque curves.

10 M

5 (b)
Explain the working of parallel inverter employing feedback diodes. Draw the voltage and current waveforms. What care should be taken to avoid commutation failure.

10 M

6 (a)
Using block diagrams discuss different configurations of UPS.

10 M

6 (b)
Draw and explain the operation of flyback converter with relevant waveforms.

10 M

7 (a)
Effect of source inductance of performance of converter.

7 M

7 (b)
Harmonic reduction in inverters.

7 M

7 (c)
Selection of battery in UPS.

7 M

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