Monday, June 23, 2014

Alternators related Interview Questions with Answers

Frequently Asked Interview Questions on Alternators
In this post we had given few Alternators related Interview questions with solutions. We believe that it will be helpful for your interview preparation. Please leave your comments in comments section.

[Q] What is meant by synchronising the alternators?
The process of connecting two or more alternators in parallel for supplying a common load is called synchronising.

[Q] What are the conditions to be satisfied for proper synchronising of alternators?
(i) The terminal voltage of the incoming alternator must be the same as bus-bar voltage.
(ii) The speed of the incoming alternator must be such that its frequency equals to the bus-bar frequency
(iii) The phase sequence of the incoming alternator must be the same as that of the other alternators or busbars.

[Q] What are the advantages of Parallel operation of alternators?
(i) It ensures continuity of power supply to consumers in case of breakdown of an alternator in an generation station.
(ii) This is economical and improves the efficiency of the generating station.
(iii) When the demand of power increases, new alternators can be installed to operate in parallel.
(iv) It is not possible to built single large size alternator to meet the requirement.

[Q] What are types of rotors used in alternators?
There are two types of rotors used in alternators namely
(i) Salient pole rotor
(ii) Smooth cylindrical type rotor

[Q] What are the advantages of providing damper winding?
The damper winding is useful in preventing the hunting ( momentary speed fluctuations) in generators.
The damper winding also used to maintain balanced 3 phase voltage under unbalanced load conditions.

[Q] What are the various methods to determine the voltage regulation of the large alternators?
In case of small machines, the regulation can be found by direct loading.
For large alternators, to find the voltage regulation indirect methods are used. They are
(i)Synchronous Impedance Method.
(ii) The Ampere-turn method.
(iii) Zero power factor or Pointer Method.

[Q] What is the basic principle of alternators?
Alternators is noting but a AC generators. They operate on the fundamental principle of electromagnetic induction as dc generators.
ie, when the rotor rotates, the emf is induced in the stator.

[Q] Which type of rotor is suitable for low speed alternators? salient pole type or cylindrical type rotor?
Salient pole type alternators are suitable for low and medium speed alternators. It has large number of projecting poles. It has large diameters and short axial lengths.

[Q] What is meant by turbo alternators?
High speed alternators are called as Turbo alternators.
As it runs at very high speed, salient pole rotors are not used. Smooth cylindrical type rotor is suitable for turbo alternators.

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