B.E./B.Tech. DEGREE EXAMINATION, MAY/ JUNE 2007.
Electronics and Communication Engineering
EE 253 — ELECTRICAL ENGINEERING
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A — (10 x 2 = 20 marks)
1. Write the expression for determining real, reactive and apparent power in a
three phase circuit?
2. Define voltage regulation.
3. Write the speed equation of a dc machine.
4. Name any two non-loading method of testing de machines.
5. What are all the advantages of induction motor over other motors?
6. Draw an approximate equivalent circuit of an induction motor.
7. Mention some of the special features on synchronous machine.
8. Write any two applications of reluctance motor.
9. Name the divisions of electric power system.
10. What are the choices of site for the coal fired thermal power station?
PART B — (5 X 16 = 80 marks)
11. (a) (i) The voltage across the lines of s three phase star connected generator is 11 KV. The generator supplies a 6 MW load at 0.8 lagging power factor. Calculate the active and reactive components in each of the generator? (8)
(ii) Draw the circuit diagram and explain the theory of three phase power measurement by two wattmeter method. (8)
(b) (i) Explain the principle of operation of Single phase Transformer (8)
(ii) A 150 KVA, 2400/240 V Transformer has R2 = 0.002 ohm, X2 = 0.45 ohm. Calculate the primary induce emf. (8)
12. (i) Explain the principle of operation of DC motor. (8)
(ii) Draw the schematic diagram ofall types of DC machines. (8)
Explain the Swinburne's test of predetermination of efficiency of a DC Machine as generator and motor. (16)
13. (a) Develop an equivalent circuit of an induction motor from first principle. (16)
(b) Explain the various starting methods of squirrel cage induction motor. (16)
14. (a) With the help of schematic diagrams, explain the constructional details of synchronous machine. (16)
(b) Calculate the percentage voltage regulation for a three phase star connected 2500 KVA, 6600V alternator operating at full load and (1) 0.8 power factor lagging, (ii) 0.8 power factor leading. The per phase synchronous reactance is 10.4 ohm. Neglect armature resistance. (16)
15. (a) Draw the schematic diagram depicting the structure of a power system and explain each major divisions. (16)
(b) Write short notes on: (16)
(i) HVDC transmission
(ii) Underground cables.