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AG-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) Derive an expression for delta to star transformation with their usual meaning?

(b) State Superposition theorem and determine the current through 6 resistor in fig.1 using superposition theorem.

Fig.1

(c) Find the value of RL in the circuit of fig.2 such that the maximum power transfer takes place. Also calculate maximum power

transferred.

Fig.2

2. Attempt any two parts: (a) Find the average value, rms value and form factor of the sinusoidal

current waveform.

(b) A series R-L-C circuit R = 10 , and L = 0.1 H and C = 8 F.

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determine: (i) Resonant frequency (ii) Q-factor of the circuit at resonance (iii) The half power frequencies

(c) What are filters? Explain different types of filters? 3. Attempt any two parts:

(a) Define the following: i. Flux ii. Reluctance iii. Hysteresis

iv. Magnetic Leakage v. Eddy Current Losses

(b) Derive the general emf equation of a single phase transformer. (c) Explain the open circuit test on a transformer.

4. Attempt any two parts: (a) With a neat diagram, explain the construction of a general D.C.

machine. (b) Draw and explain the speed torque characteristics of a DC Shunt

motor. (c) What is armature voltage control of separately excited motor?

5. Attempt any four parts: (a) Explain the principle of operation of three phase induction motor.

(b) Describe double field revolving theory of single phase induction motor.

(c) What are the disadvantages of low power factor? (d) Define slip in case induction motor.

(e) Draw slip-torque characteristics of a three phase induction motor. (f) Why single phase induction motor is not self starting?