B.E EEE Nov Dec 2011 Question Paper: EE52 Electrical Machines - II Fifth Semester Anna University of Technology, Coimbatore

ANNA UNIVERSITY OF TECHNOLOGY, COIMBATORE

B.E./B.Tech. DEGREE EXAMINATION, November/December 2011

FIFTH SEMESTER - EEE

ELECTRICAL MACHINES II

Time : Three hours Maximum : 100 Marks

Answer ALL Questions

PART A - (10 X 2 = 20 Marks)

1. Why altemators are rated in kVA not in kW?

2. Why short pitch windings are preferred over full pitched winding?

3. What are the causes of changes in voltage of altemators when loaded?

4. What does hunting of synchronous motor mean?

5. Define slip of an induction motor.

6. What is induction generator?

7. Is it possible to add an external resistance in the rotor circuit of a cage induction motor? Justify your answer.

8. Mention the methods to change the speed of an induction motor.

9. Why the single‘phase induction motors are not self Starting one?

10. Mention the applications of stepper motor.

PART- B (5 X 16 = 80 MARKS)

11. a. Explain the construction and working principle of synchronous machines in detail (8)

b. The open circuit and short circuit test readings for a 3-phase star connected 1000 kVA, 2000V, 50 Hz synchronous generators are.....

EE52 Electrical Machines - II Fifth Semester Anna University of Technology, Tirunelveli, B.E EEE Nov Dec 2011 Question Paper

ANNA UNIVERSITY OF TECHNOLOGY, TIRUNELVELI

B.E./B.TECH. DEGREE EXAMINATION, November/December 2011

FIFTH SEMESTER - EEE

ELECTRICAL MACHINES 11

Time : Three hours MaXimum i 100 Marks

Answer ALL Questions

PART A - (10 X 2 = 20 Marks)

1. What do you mean by synchronous reactance?

2. What is the purpose of conducting slip test?

3. Is synchronous motor inherently self-starting or not.

4. State any two methods of starting synchronous motor.

5. What are the losses produced in induction motor?

6. Write down the equation for running torque of an induction motor.

7. Why induction motor draws large current from the supply during starting?

8. How many speeds you can obtain by cascaded connection of induction motors?

9. Why is the single phase induction motor having two winding in this stator?

10. State any two applications capacitor start run induction motor.

PART-B (5 X 16 = 80 MARKS)

11. a. 1) Explain the effects of armature reaction for different power factor loads. (8)

Question Paper of EE52 Electrical Machines - II Fifth Semester Anna University Trichy, B.E EEE November December 2011

ANNA UNIVERSITY OF TECHNOLOGY, TRICHY

B.E./B.TECH. DEGREE EXAMINATION, November/December 2011

FIFTH SEMESTER - EEE

ELECTRICAL MACHINES II

Time : Three hours    Maximum : 100 Marks

Answer ALL Questions

PART A - (10 X 2 = 20 Marks)

1. Define distribution factor.

2. What is damper winding? Why is it used?

3. Why does the synchronous motor develop torque only at synchronous speed?

4. What is a phase advancer?

5. Why three phase induction motor called singly excited motor?

6. Define slip.

7. How can speed of three phase induction motor be controlled?

8. What is induction generator?

9. Define step angle.

10. How will you change the direction of rotation of a split phase induction motor?

PART B - (5 x  16 = 80 MARKS)

11. a. Explain in detail MMF method of predetermining the voltage regulation of the alternator. (8)

b. A 4 -pole 3 phase, 50 Hz star connected alternator has 60 slots, with four conductors per slot. Coils are short pitched by three slots. If the phase spread is 60°, find the line induced voltage for a flux per pole of 0.943 Wb distributed sinusoidally in space. All the turns per phase are in series. (8)

or

12. a. Derive the expression for synchronizing current, power and torque. (10)

b, Calculate the maximum load on a 5 MVA, three phase alternator having a synchronous reactance of 5 ohm can deliver when connected to 6.6 kV bus bar if its excitation is such that the emf on open circuit is 6 kV. Find the armature current and power factor at this load. (6)

13. a. Derive an expression for power developed in a synchronous motor. (8)

b, A 3300 V, 1.5 MW, 3-phase Y connected synchronous motor has X d = 4 ohm per phase and Xq = 3 ohm per phase. Neglecting all losses, calculate the excitation EMF. When motor supplies rated load at unity PF. Calculate the maximum mechanical power would develop for this field excitation. (8)

Question Paper of Anna University Chennai, EE52 Electrical Machines - II Fifth Semester B.E EEE November December 2011

ANNA UNIVERSITY

B.E./B.TECH. DEGREE EXAMINATION, November/December 2011

FIFTH SEMESTER : EEE

ELECTRICAL MACHINES II

Time : Three hours       Maximum : 100 Marks

 Answer ALL Questions

PART A - (10 X 2 = 20 Marks)

1. What do you mean by single layer and double layer winding?

2. What are the various function of damper winding provided with alternator?

3 What is a synchronous capacitor?

4. What are V-curves?

5. What are the rotor slots of a 3-phase induction, motors skewed?

6. Define slip of induction motor.

7. State the effect of rotor resistance on starting torque. 

8. What are the various method of speed control of 3-phase induction motor

9. What type .of motor is used for ceiling fan?

10. State the application of shaded pole motor.

PART B (5 X 16 = 80 MARKS)

11. a. i) Derive from first principle, the emf of 3-phase alternator. (8)

ii) The following open circuit and short circuit test are made on a 6000 kVA, 6600 V, star connected, 2-pole; 60 Hz turbine driven alternator. If I = 125 A, at open circuit terminal voltage = 8200 V with armature short circuited I = 125 A (line). At the rated load and upf armature loss is 1.5%.of output.

Determine the percentage regulation at rated load and 0.8 p.f. lag. (8)

or

b. 1) Explain how will you determine the d and q-axis reactance of a synchronous machine in your laboratory. (3)

ii) For the salient synchronous machine, derive the expression for power developed as a function of load angle. (3)

B.E/B.Tech Degree Examinations May / June 2011 Anna University EE52 Electrical Machines - II Question Paper

B.E/B.Tech Degree Examinations May / June 2011

Regulations 2008

Fifth Semester - EEE

EE52 Electrical Machines - II

Electrical and Electronics Engineering

Time : 3 hours  Max. Marks : 100

Part-A (10 x 2 = 20 marks)

Answer all Questions

1. What are the effects of Armature reactor?

2. State the condition for parallel operations of Alternator.

3. List any two characteristic features of synchronous motor.

4. What is the synchronous condenser?

5. Why is the Induction motor always runs with the speed less than the synchronous speed?

6. Define slip.

7. What is the need for starters in Induction motor?

8. What are the speed control techniques applicable to squirrel cage induction motor?

9. Define double field revolving theory.

10. Write down any two applications of single phase induction motors

.

Part-B (5 x 16 = 80)

11. a) i. Derive the emf equation of Alternator. (8)

Question Paper of Anna University of Technology Coimbatore, EE52 Electrical Machines - II Fifth Semester B.E EEE April May 2011

ANNA UNIVERSITY OF TECHNOLOGY, COIMBATORE

B.E./B.TECH. DEGREE EXAMINATION, April/May 2011

FIFTH SEMESTER - EEE

ELECTRICAL MACHINES II

Time : Three hours  Maximum : 100 Marks

Answer ALL Questions

PART A - (20 X 2 = 40 Marks)

1. Name the main parts of synchronous generator.

2. Write down the EMF equation of alternator.

3. Define regulation of alternator. '

4., Name the different methods of determining the voltage regulation of synchronous generator.

5. Synchronous motor always runs at synchronous speed why?

6. What is hunting?

7. What are V-curves?

8. What are the uses of damper winding in a synchronous motor?

9. How will you change the direction of rotation of three phase induction motor?

10. What is Slip?

11. List the application of slip ring induction motor?

12. Why an induction motor is called asynchronous motor?

13. What is the disadvantages of dynamic braking of an induction motor?

14. What is eddy current loss?

15. How does the slip vary with load?

16. Is it possible to start 3-phase slip ring induction motor on load?

17. What kind of motor is used in a mixie?

18. In which direction does a shaded pole induction motor run?

19. Why single phase induction motor has low power factor?

20. .What do you mean by split phase motor?

PART B (5 x 12 =  60 Marks)

Answer any five questions

21. Explain the double field revolving theory for Operation Of Single Phase induction motor.

22. Explain the principles of operation and applications of repulsion motor and hysteresis motor.