Other Bachelor Degree- ELECTRICAL MACHINES (Karunya University, Coimbatore-2010)
Saturday, 24 August 2013 07:35anudouglas
Karunya University
(Karunya Institute of Technology and Sciences)
(Declared as Deemed to be University under Sec.3 of the UGC Act, 1956)
End Semester Examination – November/December 2010
Subject Title: ELECTRICAL MACHINES Time: 3 hours
Subject Code: 09EI220 Maximum Marks: 100
Answer ALL questions
PART – A (10 x 1 = 10 MARKS)1. If field resistance of a d.c. shunt generator is increased beyond its critical value, the generator output voltage ________.
2. The condition for maximum power developed by the motor is ________.
3. Transformer cores are laminated in order to ________.
4. Give the condition for maximum efficiency of a transformer.
5. Classify the types of induction motor based on rotor construction.
6. What is a synchronous capacitor or condenser?
7. Name the two theories used to explain the behavior of the single phase induction motor.
8. Name the motor which may be operated either on direct or single-phase a.c. supply.
9. Name the heating method which is based on the transformer principle.
10. Name the dc motor especially used for traction and why.
PART – B (5 x 3 = 15 MARKS)
11. List out the different types of the characteristic curves of a motor.
12. Why is transformer rating in kVA?
13. List out the features of synchronous motor.
14. Write down the principle of servomotors.
15. State the use of electricity in welding and give its two types.
PART – C (5 x 15 = 75 MARKS)
16. a. List out the necessary conditions for build-up of a shunt generator. (5)
b. Discuss in detail about Ward Leonard Speed Control with diagram. (10)
(OR)
17. a. The armature winding of a 4-pole, 250 V d.c shunt motor is lap connected. There are 120 slots, each slot containing 8 conductors. The flux per pole is 20 mWb and current taken by the motor is 25A. The resistance of armature and filed circuit are 0.1 and 125W respectively. If the rotational losses amount to be 810 W find,
i) Gross torque (Ta) ii) Useful torque (Tsh) (iii) Efficiency. (10)
b. Define torque and derive its equation for the motor. (5)
18. a. Derive the E.M.F equation of the single phase transformer. (12)
b. A 2,200/250-V transformer takes 0.5 A at a p.f. of 0.3 on open circuit. Find magnetizing and working components of no-load primary current. (3)
(OR)
19. Obtain the equivalent circuit of a 200/400-V, 59-Hz, 1-phase transformer from the following test data:
O.C. test : 200 V, 0.7A, 70 W – on L.V. side
S.C. test : 15V, 10A, 85 W – on H.V. side.
Calculate the secondary voltage when delivering 5 kW at 0.8 p.f. lagging, the primary voltage being 200V.
[P.T.O]
20. a. Explain in detail about Torque-slip characteristics of the induction motor. (10)
b. List out the advantages of having stationary armature. (5)
(OR)
21. a. Discuss in detail about different torques of a Synchronous Motor. (8)
b. Give the comparison between Synchronous and Induction Motors. (7)
22. a. Explain in detail about linear induction motor and its properties. (5)
b. Explain briefly about Single-value Capacitor Start –and- Run Motor. (10)
(OR)
23. Explain briefly about Variable Reluctance Stepper Motors with full step operation.
24. a. List out any five requirements of a good heating element. (5)
b. Explain briefly about dielectric heating and mention its advantages. (10)
(OR)
25. a. Explain in detail about the advantages and limitation of electric traction. (10)
b. Discuss briefly about Series-Parallel starting method in electric traction. (5)
| Earning: ₹ 0.00/- |
