ELECTRICAL ENGINEERING EC2201 ANNA UNIVERSITY NOVEMBER/DECEMBER 2011 QUESTION PAPER | EC2201 ELECTRICAL ENGINEERING ANNA UNIVERSITY QUESTION PAPER

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

Third Semester

Electronics and Communication Engineering

EC 2201 — ELECTRICAL ENGINEERING

(Regulation 2008)

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A — (10 × 2 = 20 marks)

1. Draw the external characteristics of a DC series generator.
2. What do you mean by Back emf?
3. What is the purpose of conducting short-circuit test on a Transformer?
4. Define transformation ratio of the transformer.
5. A 6 pole, 3-phase Induction motor operating on a 50 Hz supply has a rotor
emf frequency as 2 Hz. Determine the rotor speed.
6. What are the types of induction motor?
7. What is the principle of hysterisis motor?
8. What is meant by pitch factor?
9. Draw the one line diagram of a power station with output transformer.
10. Compare AC and DC transmission system.


PART B — (5 × 16 = 80 marks)


11. (a) Explain the constructional details of a DC machine with neat diagrams. (16)

Or

(b) (i) Explain the principle of operation of DC motor with relevant diagrams. (8)
(ii) Explain the procedure for Swinburne’s test. How to find the efficiency of a DC Motor and DC generator using this test? (8)
12. (a) (i) Explain the operation of transformer on no load and on load with vector diagrams. (10)
(ii) Derive the emf equation of a transformer. (6)

Or

(b) (i) Explain the open circuit and short circuit test on transformers.(8)
(ii) Derive the transformer equivalent circuit. (8)
13. (a) (i) Explain the principle of operation of three phase induction motor. (8)
(ii) A single phase equivalent circuit of a 6-pole SCIM that operates from a 220 V line voltage at 60 Hz is given below. Calculate the stator current, output power, torque and efficiency at a slip of 2.5%. The fixed winding and friction losses are 350 W. Neglect the core loss. (8)

Or

(b) (i) Explain any two methods of speed control of induction motor from stator side. (8)
(ii) Describe why single phase induction motors are not self starting by using double field revolving theory. (8)


14. (a) (i) Explain the tests to be conducted for finding the voltage regulation in a three phase synchronous generator emf method.(6)
(ii) A three-phase star connected generator has a terminal voltage of 3300 V and delivers a full-load current of 100 A. On short circuit a field current of 5 A was necessary to produce the full load current. The emf on open circuit for the same excitation was 900 V. The armature resistance was 0.8 ohms/phase.
Determine the full load voltage regulation (1) 0.8 pf lagging and(2) 0.8 pf leading. (10)

Or

(b) (i) Explain the construction and working principle of Reluctance motor. (8)
(ii) What is the principle of stepper motor? Describe the working of variable reluctance type Stepper motor. (8)
15. (a) (i) Explain any four type types of insulators used for overhead transmission systems. (8)
(ii) Explain with a neat sketch the Layout of hydel power plant. (8)

Or

(b) Draw the schematic layout of a substation and hence explain the various instruments associated with it. (16)