Interview Questions.

Question 1. What Is A Generator?

Answer :

A Generator is a system which converts Mechanical Energy into Electrical Energy.

Question 2. On Which Principle A Generator Works?

Answer :

Generator works on Faradays legal guidelines of “Electro Magnetic Induction ”

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Question three. What Are Faraday's Laws Of Electro Magnetic Induction?

Answer :

First Law: Whenever a conductor cuts magnetic flux and E.M.F is prompted in that conductor.

Second Law: The significance of the caused e.M.F. Is same to the price of trade of flux linkage.

Question 4. What Are The Two Main Parts Of An Ac Generator?

Answer :

Stator
Rotor
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Question five. What Is The Main Difference Between An Ac Generator And Dc Generator?

Answer :

In an AC Generator the field is rotating and the armature is stationary whereas in DC Generator the sector is desk bound and the armature is rotating.

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Question 6. What Are The Advantages Of Stationary Armature And Rotating Field In An Ac Generator?

Answer :

It is easy to take output from the desk bound armature.
It is less complicated to insulate stationary armature for better voltage.
Low voltage excitation deliver may be effortlessly supplied to the rotor through slip rings.
Question 7. What Is The Relation Between The Frequency, Pole And Speed Of A Generator?

Answer :

F = PN/a hundred and twenty Hz

   Where P is the No.Of Poles

              N is the Speed in RPM.

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Question 8. In A Generator With 2 Pole, And Speed 3000 Rpm, What Is The Frequency Of The Induced Emf ?

Answer :

F = PN/a hundred and twenty

= 2 x 3000/120

  = 50 Hz.

Question 9. What Is The Connection Of Winding In A Stator?

Answer :

Double superstar connection.

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Question 10. What Is The Efficiency Of A Generator?

Answer :

98.Fifty five%

Question eleven. What Is The Coolant Used To Cool Stator Winding?

Answer :

Demineralised water

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Question 12. What Is The Coolant Used To Cool Rotor Winding?

Answer :

Hydrogen.

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Question 13. What Are The Advantages Of Hydrogen Gas As Coolant Over Others?

Answer :

Density is 1/14 of air.
Windage loss is low.
Low noise.
Heat switch co efficient is 1.5 times better than air.
Thermal conductivity is 7 instances better than air.
Question 14. What Are The Losses In A Generator?

Answer :

Stator copper
Stator iron
Rotor copper
Windage loss 
Stray loss
Friction loss
Question 15. What Is Short Circuit Ratio (scr) Of A Generator?

Answer :

It is the ratio of the sector cutting-edge required to produce rated voltage on open circuit to the sphere modern required to circulate rated current on brief circuit.

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Question sixteen. What Is The Value Of Scr In A 210 Mw Turbo Alternator?

Answer :

SCR = 0.Forty nine

Question 17. Why Over Current Protection Is Not Necessary For Modern Generators?

Answer :

Over Current safety is not needful for cutting-edge alternators due to the fact these are capable of withstanding a complete brief circuit at their terminals for enough time without an awful lot over heating and damage.

Question 18. What Type Of Protection Is Provided For The Generators Against Over Heating Of The Generator Stator?

Answer :

Resistance temperature detector.

Generator Operator Interview Questions
Question 19. Which Type Of Relays Are Used For The Merz-rate Protection System For Alternator?

Answer :

Merz-Price protection is differential protection supplied for the alternator. The relays used in the Merz-Price safety device of alternator are immediate electro-magnetic type safety.

Question 20. Why Large Alternator Is Grounded With Large Resistance?

Answer :

Large capacity of alternators are commonly supplied with resistance grounding. High fee of resistor is connected to the neural route to the ground. If the generator is delta related, then it's far grounded with the assist of zig-zag transformer or (Delta-Star) transformer such that a excessive resistor is hooked up between the impartial factor and the floor. Resistance grounding is furnished so that it will restriction the quick circuit modern flowing for the duration of earth fault to stator winding that allows you to provide safety towards mechanical stresses and melting of winding throughout Line to Ground brief circuit. In big turbines fault cutting-edge is limited as low as 10 to fifteen amperes all through short circuit.

Question 21. Why It Is Not Necessary To Provide Protection For Turn To Turn Fault In Alternator?

Answer :

The coils of the modern alternators are single flip and consequently it is not vital to offer safety for turn to show faults.

Question 22. Why It Is Necessary To Suppress Field Immediately After Disconnection Of Faulty Alternator From The System?

Answer :

In the occasion of fault on the generator windings even though the generator circuit breaker is tripped, the fault is continuous to fed so long as the excitation will exist because the emf is triggered in the generator. Hence it's far important to suppress the field right now after disconnecting the defective generator from the system.

Question 23. Why It Not Necessary To Provide Over-voltage Protection In Turbo-alternator?

Answer :

The over voltage happens when the top mover speed will increase due to unexpected lack of the weight at the generator and the speed control governors in case of turbo-turbines are very touchy to the rate variations and consequently generator over voltage of considerable duration or significance does not generally arise. This is the reason why turbines aren't supplied with over voltage safety.