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# EE6504 Electrical Machines 2 Important questions

## Sample EE6504 Electrical Machines 2 Important questions:

1. What are the conditions for parallel operation of an alternator? [Nov/ Dec 2009], [June/July 2009]

i. The terminal voltage of the incoming alternator must be the same as that of bus bars.
ii. The frequency of incoming alternator must be same as that of bus bars.
iii. The phase sequence of the incoming machine voltage must be same as that of bus bar voltage .

2. Why is EMF method called pessimistic method? [Apr/ May 2007]

The value of voltage regulation obtained by emf method is always more than the actual value and therefore it is called pessimistic method. (EE6504 Electrical Machines 2 Important questions)

3. What are the causes of changes in voltage of alternators when loaded? [Apr/ May 2006] [Nov/ Dec 2011]

i. Voltage drop due to resistance of winding
ii. Voltage drop due to leakage reactance
iii. Voltage drop due to armature reaction

4. Write down the equation for frequency of emf induced in an Altenator. [June/July 2009]
Frequency of emf induced in an Alternator,(f) ,expressed in cycles per second or Hz, is given by the following equation f = (PN)/120: Hz, Where P- Number of poles N-Speed in rpm.

5. What is the purpose of conducting slip test? [Nov/ Dec 2009]
The slip test is performed on an alternator to determine Xd and Xq. (EE6504 Electrical Machines 2 Important questions)

6. Two reaction theory is applied only to salient pole machines. State the reasons. [Nov/ Dec 2007]
A multipolar machine with cylindrical rotor has a uniform airgap and therefore, its reactance remains the same, irrespective of the special positions of the rotor but in case of salient pole machines, the airgap is not uniform and its reactance varies with the rotor positions. Because of nonunifomity of the reluctance of the
magnetic paths, the mmf of the armature is divided into two components viz, (i) one component is located along the axis of salient pole rotor known as direct axis component. (ii) the other component is located perpendicular to the axis of salient pole rotor known as quadrature axis component. This makes the concept of
two reaction theory. (EE6504 Electrical Machines 2 Important questions)

 Subject Name Electrical Machines 2 Subject Code EE6504 Regulation 2013 File PDF