ELECTRICAL ENGINEERING ANNA UNIVERSITY NOV/DEC 2011 QUESTION PAPER for ECE dpt (3rd Semester) ...

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.

B.E. â€" Electronics and Communication Engineering

Third Semester

131307 â€" ELECTRICAL ENGINEERING

(Regulation 2010)

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A â€" (10 * 2 = 20 marks)

1. Distinguish between shunt and series field coil construction in DC machine?
2. What is the necessity of starter in dc motors?
3. What are the applications of step-up and step-down transformers?
4. Define regulation and efficiency of the transformer.
5. Why an induction motor never runs at its synchronous speed?
6. What is the function of a capacitor in single phase induction motor?
7. What is hunting how can it be prevented?
8. What are the advantages of stepper motor? Give the applications of stepper
motor?
9. What are the major electrical equipments used in the power system?
10. How cables are classified according to the voltage?

PART B â€" (5 ´ 16 = 80 marks)

11. (a) (i) Sketch and explain the speed-current, speed-torque and torquecurrent
characteristics of a DC shunt and series motor. (8)
(ii) Derive the expression for emf generated in d.c. machine. (8)
Or
(b) (i) Explain in detail about the ward-leonard system of speed control of
DC motor. (8)
(ii) Draw a neat sketch and explain a 3 point starter. (8)
12. (a) (i) Draw and explain the no load vector diagram of ideal transformer
and practical transformer. (8)
(ii) Enumerate the various losses in a transformer. Derive the condition
for maximum efficiency. (8)
Or
(b) (i) Derive the equivalent circuit of single phase t wo winding
transformers. (6)
(ii) A 250/500 V, 50Hz single phase transformer gave the following test
result (10)
SC test : 20V, 12A, 100 W with low voltage winding shorted.
OC test : 250V, 1A, 80 W with high voltage winding shorted.
Obtain the equivalent circuit parameters and draw the equivalent
circuit referred to primary.
13. (a) (i) List the differences between squirrel cage and slip ring induction
motors. (8)
(ii) Derive the torque equation of a three phase induction motor. Sketch
the torque-slip characteristics of a 3-phase IM. (8)
Or
(b) (i) Discuss the various methods of speed control in a 3-phase IM. (8)
(ii) Explain the working principle of single phase induction motor. Why
single phase induction motor is not self starting. (8)
14. (a) (i) Explain the construction and working principle of a synchronous
motor. (8)
(ii) Define voltage regulation. Explain the two methods used to
determine voltage regulation of alternators. (8)
Or
(b) Write short notes on : (16)
(i) reluctance motor
(ii) stepper motor
(iii) hysteresis motor.
15. (a) (i) Draw the structure of power system with single line representation.
Show its essential constituent sections. (8)
(ii) What are the advantages and disadvantages of HVDC
Transmission? (8)
Or
(b) (i) Explain in detail various types of insulators and their applications
to power transmission. (8)
(ii) Draw the schematic layout of a substation and explain. (8)