23041-ELECTRICAL MACHINES II IMPORTANT QUESTIONS

KUMARAN POLYTECHNIC COLLEGE

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

23041-ELECTRICAL MACHINES II

STAFF-IN-CHARGE: N.SURESH KUMAR

IMPORTANT QUESTIONS

UNIT-I

PART-A

1.      Write the expression for distribution factor.

2.      Write any one advantage of rotating type field in the 3 phase alternator.

3.      What is slot angle with respect to 3 phase alternator?

4.      Write any one merit of hydrogen cooling method of alternator.

5.      Define Pitch factor

6.      What type of rotor has been used in turbo alternator?

7.      Write any two advantages of Short chorded winding

8.      Define fractional Pitched Winding

9.      Define slot angle

10. Explain the term Double layer

11. Calculate the distribution factor for 48 slots 4 pole single layer 3 phase winding

12. Write the EMF equation of an alternator

PART-B

1.      Derive the EMF Equation of an Alternator. (12)

2.      What are the advantages of Hydrogen cooling. (12)

3.      Explain the basic principles of salient pole type alternator with the help of a neat diagram. (12)

4.      Explain the constructional details of stator and rotor of a salient pole Alternator with neat diagram..

5.      Explain the methods adopted to obtain sine wave shape of emf induced in the alternator.

UNIT-II

PART-A

1.      Write the equation of voltage regulation of alternator.

2.      What is armature reaction with reference to alternator?

3.      What is necessity of parallel operation of alternator?

4.      What is the use of circle diagram?

5.      Define synchronous reactance

6.      On what condition the switch should be closed by Dark lamp method?

7.      What are the types to find voltage regulation in alternator?

8.      Write any one effect of changing excitation of alternator?

9.      Draw the Load characteristic of an alternator

10. On what condition the switch should be closed by Dark lamp method?

11. Write any two causes for voltage drop in alternator

12. What are the conditions for parallel operation of two alternators?

13. What is armature leakage reactance?

PART-B

1.    What are the causes of voltage drop in alternator? Draw the vector diagram of a loaded alternator and determine the voltage regulation.

2.    Explain the synchronizing of alternator by dark lamp method.

3.    Explain load sharing of two alternator

4.    An alternator has the following data (i) 3 phase alternator (ii) no. of poles =8 (iii) distribution factor=.985 (iv) flux/pole=.040 Wb (v) no. of slots on the armature=90 (vi) no. of conductor/slot=8 (vii) full pitched winding (viii) speed of alternator=600rpm. Determine the no load terminal voltage.

5.    Draw neat circuit diagram and briefly explain open circuit and short circuit test.

6.    An alternator has the following data (a). Number of phases is 3 (b)Number of slots on the Armature is 90 (c)Number of poles is10 (d)Number of conductor per slot is 8 (e)Distribution factor is 0.965 (f)full pitched winding (g)flux per pole is 0.040 wb (h)speed of alternator is 600 rpm (i)Connection is star. Determine No Load Terminal voltage.

7.    Explain Armature reaction of an Alternator

8.    Briefly explain effect of change in excitation

UNIT-III

PART-A

1.      What is slip with reference to three phase induction motor?

2.      Write any two applications of 3 phase Induction motor

3.      What are different types of speed control in 3 phase induction motor?

4.      Write the expression of synchronous speed in 3 phase induction motor.

5.      Compare slip ring and cage motor. (any one point)

6.      Write the expression for rotor emf equation of 3 phase induction motor.

7.      What is crawling?

8.      What is the condition for maximum starting torque?

9.      What are the types of rotor?

10. What is the use of circle diagram?

11. Write the Slip Equation

12. Draw the Slip-Torque characteristic curve

13. Which type of lamination is done by core in squirrel cage rotor?

14. What is the use of pole changing method?

PART-B

1.      Explain No load and Blocked rotor test of 3 phase induction motor.

2.      Explain how rotating magnetic field is produced in 3 phase induction motor by explaining the principle of its operation by means of a neat diagram.

3.      Compare squirrel case and slip ring Induction Motor

4.      Explain star delta starter with the help of the control diagram.

5.      Explain Rotating Magnetic Field produced by 3 phase 2 pole system

6.      Explain Rotor Resistance starter with a neat diagram

UNIT-IV

PART-A

1.      What are the two types of single phase capacitor type motor?

2.      Write the applications of synchronous motor.

3.      Write any two methods of starting of synchronous motor

4.      Mention any one application of single phase capacitor start induction motor.

5.      Is synchronous motor is self starting.

6.      Write any two applications of split phase induction motor

7.      What is the principle of synchronous motor?

8.      What is the name used in the motor having the lowest rating than 1 HP?

9.      What are the two types winding used in single phase motor?

10. What is the use of centrifugal switch?

11. Which type of Motor is used in Drilling Machine?

PART-B

1.      Explain ‘V’ Curve and Inverted ‘V’ curve of synchronous motor.

2.      Explain principle of working Split Phase Induction Motor

3.      Explain effect of excitation on armature current and power factor of a synchronous motor.

4.      Explain the double field revolving theory for single phase induction motor with neat diagram

5.      Explain capacitor Start and Run Motor with a neat diagram

UNIT-V

PART-A

1.      Write any one quality of good transformer oil.

2.      How will you measure earth resistance?

3.      List any two types of oil purification.

4.      Write any one point to take care of bearing of 6 phase induction motor.

5.      What are common troubles in Induction Motor?

6.      Write the cases of noise and vibration of induction motor.

7.      What do you understand by vacuum impregation?

8.      Which instrument is used to measure the insulation resistance?

9.      What are the types of Balancing?

10. What is the B.D.V. value of good transformer oil?

11. Define single phasing

12. State any two installation procedure when an induction motor is installed.

13. What is mean by voltage test?

14. Define earthing

PART-B

1.      What are the causes of noise and vibration of an Induction Motor

2.      Explain any five points to be followed in installation and commissioning of induction motor.

3.      Explain any one method of Oil Purification

4.      Write any six points for the common troubles and their remedies for induction motor starters

5.      Explain continuity test and short circuit on distribution Transformer

6.      Explain Transformer Earthing and Measurement of Earth Resistance.

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