Anna University Chennai 2005 B.E ELECTRICAL ENGINEERING - Question Paper

ans any 3 ques.. every ques. carries 14 marks.

Q.2 a. Draw and discuss the phasor diagram of a transformer on load at a lagging power factor. (7)
b. Calculate the voltage regulation of a transformer in which ohmic drop is 2% and the reactance drop in 5% of the voltage at 0.8 lagging power factor. (7)
Q. 3 Explain with proper phasor diagrams the operation of a three phase synchronous machine with normal excitation at the subsequent conditions :
(i) The machine is floating on the supply bus.
(ii) The machine is working as a synchronous motor at no load.
(7)

(7)
Q.4 a. Derive the expression of torque produced in a d.c. motor. (7)
b. A 230 V d.c. shunt motor with constant field drives a load whose torque is proportional to the speed. When running at 750 rpm it takes 30 A. obtain the speed at which it will run if a 10 ohm resistance is connected in series with the armature. The armature resistance may be neglected. (7)
Q.5 a. Draw the torque speed characteristics of a three phase induction motor and clearly indicate the effect of change in rotor resistance. (7)

b. The power input to a 500 V, 50 Hz, six pole three phase squirrel cage induction motor running at 975 rpm is 40 KW. The stator losses are one KW and the friction and windage losses are two KW. Calculate (7)
(i) Slip (ii) rotor copper loss
(iii) mechanical power developed (iv) the efficiency.
Q.6 a. For a small and sensitive servo mechanism provide 4 reasons why a.c. servo motors are generally preferred to d.c. servo motor. (7)

b.
A 120V, 60Hz, 1/4hp universal motor runs at 2000 rpm and takes 0.6A when connected to a 120V d.c. source. Determine the speed, torque and power factor of the motor when it is connected to a 120V, 60 Hz, supply and is loaded to take 0.6A (rms) of current. The resistance and inductance measured at the terminals of the motor are 20 ohm and 0.25H respectively. (7)
PART II
ans any 3 ques.. every ques. carries 14 marks.


Q. seven a. What are various kinds of resistance welding? (3)

b. What are various welding controls used in resistance welding? (4)

c. Explain the principle of high frequency induction heating. What factors control the depth of penetration of heat? provide the industrial application of this mode of heating. (7)

Q.8 a. What is the fundamental difference ranging from thermal and nuclear power plants? (3)

b. List the advantages of nuclear power plants over conventional thermal power plants. (4)

c. Discuss briefly the solid state circuits used for the stator voltage control of induction motor derives. (7)

Q.9 a. Differentiate ranging from feeder, distributor and service main. (3)

b. What are the advantages of high voltage transmission? provide its limitations also. (4)

c. Discuss the working principle of a direction over-current relay. (7)

Q.10 a. Explain the working of nickel cadmium cells with its merits and demerits over lead acid cell. (7)

b. Discuss methods of laying underground cables. (7)

Q.11 a. Write short notes on any 2 of the subsequent :-
(i) Switched reluctance motors.
(ii) Parallel operation of transformers.
(iii) Selsyns. (7 x two = 14)

Earning:   Approval pending.