Question Paper: BE-ETRX_SEM7_PE2_MAY18 Mumbai University

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## PE 2- May 2018

### Electronics Engineering (Semester 7)

TOTAL MARKS: 80

TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.

(2) Attempt any **three** from the remaining questions.

(3) Draw neat diagrams wherever necessary.

(4) Figures to the right indicate full marks.

**1**Attempt any four questions

**(a)**Explain regenerative breaking of DC motor?

**(b)**What are the disadvantage and advantages of SMPS?

**(c)**Explain the advantages of induction heating?

**(d)**Compare SVM with conventional sine wave PWM?

**(e)**Give the significance of slip in AC motors?

**2(a)**Explain in detail the principle and working of simple buck boost converter and with the help of necessary derivation and waveforms.

**2(b)**Derive and explain the average state space model of buck converter. Use this space state model to derive equation of output voltage of buck converter at equilibrium condition.($\frac{dv}{dt}=0$)

**3(a)**Derive expressions for overlap angle (µ) and output voltage for a single phase fully controlled bridge rectifier with source inductance.

**3(b)**Explain PWM as used for inverters. What are its advantages?

**4(a)**Explain any three regions in the torque slip characteristics in an induction motors which is the most stable region of operation in the torque slip characteristics. Justify your answer with suitable figure?

**4(b)**Explain method of speed control for three phase induction motor.

**5(a)**Give different methods of controlling speed of separately excited DC motor. Explain constant torque and constant power operation.

**5(b)**A 220 volt, 1300 rpm, 8A separately excited DC motor has armature resistance of 1 ohm. It is fed from single phase fully controlled bridge rectifier with an AC source voltage of 230 volts, 50 Hz. Assuming continuous load compute motor speed at firing angle 450 and torque 5Nm.

**6**Write short notes on (any three)

a) Battery charging system

b) Kramer’s drive

c) Classification of UPS

d) Harmonic reduction in inverters.