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EAG-401

(Following Paper ID and Roll No. to be filled in your Answer Book)

PAPER ID : Roll No.

B.Tech. SEM. IV (EVEN SEM.) THEORY

EXAMINATION 2014-15 ELECTRICAL CIRCUITS AND ELECTRICAL MACHINE

[Time : 3 Hours] [Total Marks : 100]

Note: Attempt all Questions. All questions carry equal marks.

1. Attempt any two parts:

(a) State and prove maximum power transfer theorem. (b) State Thevenin's Theorem. Find the current in the 10 resistor by

using Thevenins theorem in the circuit shown in fig.1

Fig.1

(c) Define the following: i. Dependent Source ii. Node

iii. Mesh iv. Junction v. Passive elements

2. Attempt any two parts:

(a) Find the average value, rms value and form factor of the waveshape as shown in fig. 2

Fig.2

2

(b) A two element series circuit is connected across an a.c. voltage source v = 300 Sin (314t + 200) volts. The current drawn is 15 Sin (314t - 100) amperes. Determine the circuit impedance magnitude and phase angle.

What is the average power drawn? (c) A series circuit has resistance of 15 and inductive reactance of

10. Calculate the value of capacitor which is connected across this series combination so that system has unity power factor. The frequency of A.C. supply is 50 Hz.

3. Attempt any two parts:

(a) What are different laws of magnetic circuits? Explain with neat diagram.

(b) Explain the construction of a transformer. What are the assumptions of an ideal transformer?

(c) Derive the condition for maximum efficiency of a transformer. 4. Attempt any two parts: (a) Explain the principle of operation of a D.C. generator. Derive emf

equation.

(b) What is need of starter in DC motors? (c) A 4 pole generator with wave wound armature has 51 slots, each

having 24 conductors. The flux per pole is 0.01 Wb. At what speed must the armature rotate to give an induced emf of 220V? What will

be the voltage developed if winding is LAP connected and the armature rotate at the same speed?

5. Attempt any four parts: (a) Discuss the important features of squirrel cage and phase wound

rotor constructions in an induction motor. (b) Describe the principle of working of a capacitor start capacitor run

single phase induction motor. (c) Explain the principle of operation of electromechanical energy

conversion. (d) Explain the method of improving power factor. (e) Derive the condition for maximum torque in 3-phase induction

motor.

(f) Why do we need starter?