Why is job preparation cooler with our interview questions site? Preparing for a job is now easier and simpler with our wisdom jobs site? Because Wisdomjobs give you all information plus all the jobs in one place. When you're interviewing for a new position, you should come prepared to answer the interview questions to win in first attempt. To be precise about a generator is a device that changes motive power into electrical power for use in an external circuit. If you are looking at Generator, Mis Executive, Clients Lead Generators , Inviting Interns/ Management Trainees, Generator Improvements & Options Engineer, Power Generation Mechanic we’ve framed multiple Generator interview questions and answers and also various Generator job roles also for your reference.
Question 1. What Is A Generator?
Answer :
A Generator is a machine which converts Mechanical Energy into Electrical Energy.
Question 2. On Which Principle A Generator Works?
Answer :
Generator works on Faradays laws of “Electro Magnetic Induction ”
Question 3. What Are Faraday's Laws Of Electro Magnetic Induction?
Answer :
First Law: Whenever a conductor cuts magnetic flux and E.M.F is induced in that conductor.
Second Law: The magnitude of the induced e.m.f. is equal to the rate of change of flux linkage.
Question 4. What Are The Two Main Parts Of An Ac Generator?
Answer :
Question 5. 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 field is stationary and the armature is rotating.
Question 6. What Are The Advantages Of Stationary Armature And Rotating Field In An Ac Generator?
Answer :
Question 7. What Is The Relation Between The Frequency, Pole And Speed Of A Generator?
Answer :
F = PN/120 Hz
Where P is the No.of Poles
N is the Speed in RPM.
Answer :
F = PN/120
= 2 x 3000/120
= 50 Hz.
Question 9. What Is The Connection Of Winding In A Stator?
Answer :
Double star connection.
Question 10. What Is The Efficiency Of A Generator?
Answer :
98.55%
Question 11. What Is The Coolant Used To Cool Stator Winding?
Answer :
Demineralised water
Question 12. What Is The Coolant Used To Cool Rotor Winding?
Answer :
Hydrogen.
Question 13. What Are The Advantages Of Hydrogen Gas As Coolant Over Others?
Answer :
Question 14. What Are The Losses In A Generator?
Answer :
Question 15. What Is Short Circuit Ratio (scr) Of A Generator?
Answer :
It is the ratio of the field current required to produce rated voltage on open circuit to the field current required to circulate rated current on short circuit.
Question 16. What Is The Value Of Scr In A 210 Mw Turbo Alternator?
Answer :
SCR = 0.49
Question 17. Why Over Current Protection Is Not Necessary For Modern Generators?
Answer :
Over Current protection is not considered necessary for modern alternators because these are capable of withstanding a complete short circuit at their terminals for sufficient time without much over heating and damage.
Answer :
Resistance temperature detector.
Question 19. Which Type Of Relays Are Used For The Merz-price Protection System For Alternator?
Answer :
Merz-Price protection is differential protection provided for the alternator. The relays used in the Merz-Price protection system of alternator are instantaneous electro-magnetic type protection.
Question 20. Why Large Alternator Is Grounded With Large Resistance?
Answer :
Large capacity of alternators are typically provided with resistance grounding. High value of resistor is connected to the neural path to the ground. If the generator is delta connected, then it is grounded with the help of zig-zag transformer or (Delta-Star) transformer such that a high resistor is connected between the neutral point and the ground. Resistance grounding is provided so as to limit the short circuit current flowing during earth fault to stator winding in order to provide protection against mechanical stresses and melting of winding during Line to Ground short circuit. In large generators fault current is limited as low as 10 to 15 amperes during 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 turn and therefore it is not necessary to provide protection for turn to turn faults.
Answer :
In the event of fault on the generator windings even though the generator circuit breaker is tripped, the fault is continuous to fed as long as the excitation will exist because the emf is induced in the generator. Hence it is necessary to suppress the field immediately after disconnecting the faulty generator from the system.
Question 23. Why It Not Necessary To Provide Over-voltage Protection In Turbo-alternator?
Answer :
The over voltage occurs when the prime mover speed increases due to sudden loss of the load on the generator and the speed control governors in case of turbo-generators are very sensitive to the speed variations and therefore generator over voltage of significant duration or magnitude does not generally occur. This is the reason why generators are not provided with over voltage protection.
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