1 (a)
Compare symmetrical and asymmetrical and semiconverter

5 M

1 (b)
What is meant by voltage and current commutation?

5 M

1 (c)
Compare series and parallel inverter.

5 M

1 (d)
What is four quadrant D.C drive?

5 M

2 (a)
Explain sinusoidal pulse width modulation as used in PWM inverter.

10 M

2 (b)
A load commutated chopper fed from 230V D.C source has a constant current of 50A. For a duty cycle of 0.4 and chopping frequency of 2 kHZ calculate:

1. Value of commutating capacitor.

2. Average output voltage.

3. Circuit turn off time for 1 ? pair of SCR?s

4. Total commutation interval

1. Value of commutating capacitor.

2. Average output voltage.

3. Circuit turn off time for 1 ? pair of SCR?s

4. Total commutation interval

10 M

3 (a)
Explain the working of single phase series inverter with appropriate circuit diagrams and waveforms.

10 M

3 (b)
Explain constant torque and constant power generation of a separately excited D.C motor. Give the schematic diagram of control unit.

10 M

4 (a)
A single phase fully controlled bridge with 230V, 50 Hz supply feeds continuous ripple free current of 20A. if L

i. Calculate overlap angle for the firing angle 60

ii. What will be the new value of the overlap angle for same firing angle if load is reduced by 50%.

_{a}=2.5mH calculate:i. Calculate overlap angle for the firing angle 60

_{o}.ii. What will be the new value of the overlap angle for same firing angle if load is reduced by 50%.

10 M

4 (b)
Draw and explain the variable voltage and variable frequency control method for 3 ? phase squirrel cage induction motor. What is the significance of v/f control.

10 M

5 (a)
A single phase full converter is used to drive separately excited D.C shunt motor with R

i. Firing angle delay for 500 RPM rated torque.

Speed of motor for firing angle ?=60

_{a}=0.25&Omega. Motor rating are 220V, 750 RPM, 50A. If input voltage to converter connected to armature is 250V ac 50 Hz. Calculate:i. Firing angle delay for 500 RPM rated torque.

Speed of motor for firing angle ?=60

^{0}at half load.
10 M

5 (b)
Explain the working of Jone?s chopper with the help of waveforms.

10 M

6 (a)
Give the advantages of flyback converter compared to forward converter. With the help of neat circuit diagram and waveform, explain the operation of isolated forward converter.

10 M

6 (b)
Using block diagram discuss different configurations of UPS.

10 M

Write Short notes on:

7 (a)
Dual converter.

10 M

7 (b)
Mc'Murray Inverter.

10 M

7 (c)
Four quadrant chopper.

10 M

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