Attempt any four from the following:

1 (a)
What are the advantages of SVM over the conventional Sine wave PWM? Explain.

5 M

1 (b)
List the merits and demerits of online and offline UPS.

5 M

1 (c)
Explain regenerative braking for DC motors.

5 M

1 (d)
Explain in brief the effect of source inductance in single phase fully controlled bridge rectifier.

5 M

1 (e)
Explain the concept of UPS and give classification of UPS system.

5 M

2 (a)
Explain clearly the steps involved in Space Vector Modulation for three phase voltage source inverter.

10 M

2 (b)
A single phase full-wave mid-point converter with freewheeling diode as shown below in Fig. Q2(b) is supplied from a 120V, 50 Hz supply with a source inductance of 0.33 mHenry. Assuming that the load current is continuous at 4A, find the overlap angle for

(i) Transfer of current from a conducting thyristor to the commutating diode.

(ii) From the commutating diode to a thyristor when the firing angle is 15 degree

(i) Transfer of current from a conducting thyristor to the commutating diode.

(ii) From the commutating diode to a thyristor when the firing angle is 15 degree

10 M

3 (a)
Derive and explain the state space model of Buck converter.

10 M

3 (b)
Explain the PI (Proportional + Integral) control of DC-DC converter with the help of neat diagram.

10 M

4 (a)
Derive the expressions for output voltage and current for a single phase fully controlled bridge rectifier with source inductance using equivalent circuit.

8 M

4 (b)
What are SMPS? Give classification and explain any SMPS circuit in detail.

6 M

4 (c)
Draw and explain the battery charging involving power electronics system.

6 M

5 (a)
A separately excited DC motor is supplied from 230V, 50Hz source through a single-phase half wave controlled converter. Its field is fed through single-phase semi-converter with zero degree firing angle delay.

Motor resistance = 0.70Ω. Motor constant = 0.5 volts sec/rad.

For a rated load torque of 15 NM at 1000 rpm and for continuous ripple free current determine:

i) Firing angle delay of the armature converter.

ii) RMS value of thyristor & free wheeling diode current.

iii) Input power factor of the armature current.

Motor resistance = 0.70Ω. Motor constant = 0.5 volts sec/rad.

For a rated load torque of 15 NM at 1000 rpm and for continuous ripple free current determine:

i) Firing angle delay of the armature converter.

ii) RMS value of thyristor & free wheeling diode current.

iii) Input power factor of the armature current.

10 M

5 (b)
Explain various methods of speed control for 3-phase induction motor.

10 M

Write short notes on:

6 (a)
Comparison of fly-back and forward converters used in SMPS.

7 M

6 (b)
Power electronics applications in induction heating.

6 M

6 (c)
Slip power recovery scheme for induction motor using Kramer Drive below sub-synchronous speed.

7 M

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