B.E /B.Tech DEGREE EXAMINATION NOVEMBER / December 2011
B.E. - Electronics and Communication Engineering
Third Semester .
ELECTRICAL ENGINEERING
(Regulation 2010)
Maximum: l00 marks
Answer ALL questions
PART A (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 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?
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 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?
11. (a) (i) Sketch and explain the speed-current, speed-torque and torque-current 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 sistem 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)
(b) (î) Derive the of single phase two winding transformers. (6)
(ii) A 250/500 V , 50 Hz single phase transformer gave the following test result:
SC test : 20V, 12 A , 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.
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)
(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.
(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)
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