What is preventive maintenance of DG Set ?
Preventive maintenance is the process of scheduled checking, replacement of parts and servicing of a machine to maintain the performance of the machine, increase the efficiency and continue the reliability of the machine.
- It is cost saving
- Increase the efficiency of the machine
- Reduce the breakdown time of the machine
- To Continue the safety of the machine
Diesel generator preventive maintenance DG checklist
There are mainly four types of dg checklist that perform on during preventive maintenance
- A check
- B check
- C check
- D check
A check- A check perform daily checking procedure of diesel generator sets.
- Check oil level in the diesel generator sets.
- Check cleanliness of diesel generator sets.
- Check battery voltage
- Check for any type of leakage
- Check all filter condition
- Check coolant level
- Check the condition v-belts
B-check-B-check perform on weekly basis or after running hours of (300-350) hours.in this type of check following parameters should be checked:
- Change oil
- Change oil filter,fuel filter and bypass filter
- Change air filter
- Change water separator
- Radiator cleaning with chemical
- Maintenance checklist of a battery
C-check-c-check performed on monthly basis or after running hours of (800-1500) hours
- Check all electrical conditions
- Check pollution level
- Change oil
- Change oil filter,fuel filter and bypass filter
- Change air filter
- Change water separator
- Radiator cleaning with chemical
D-check-D-check performed on yearly basis or after running hours of (3000—5000) hours.
- Complete dg set should be dismental.
- turbo charger service
- injector pin service
- cylinder head service
- PT pump service
- Change oil
- Change oil filter,fuel filter and bypass filter
- Change air filter
- Change water separator
- Radiator cleaning with chemical
Generator Interview Question and Answer.
1. What Is A
Generator?
Answer :
A Generator is a machine which converts Mechanical Energy into Electrical Energy.
2. On Which
Principle A Generator Works?
Answer :
Generator
works on Faradays laws of “Electro Magnetic Induction ”
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.
4. What Are
The Two Main Parts Of An Ac Generator?
Answer :
o
Stator
o
Rotor
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.
6. What Are
The Advantages Of Stationary Armature And Rotating Field In An Ac Generator?
Answer :
o
It is easy to take output from the
stationary armature.
o
It is easier to insulate stationary
armature for higher voltage.
o
Low voltage excitation supply can be
easily supplied to the rotor through slip rings.
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.
8. In A
Generator With 2 Pole, And Speed 3000 Rpm, What Is The Frequency Of The Induced
Emf ?
Answer :
F
= PN/120
=
2 x 3000/120
= 50 Hz.
9. What Is
The Connection Of Winding In A Stator?
Answer :
Double
star connection.
10 What Is The Efficiency Of A Generator?
Answer :
98.55%
11.What Is The Coolant Used To Cool
Stator Winding?
Answer :
Demineralised
water
12. What Is The Coolant Used To Cool Rotor
Winding?
Answer :
Hydrogen.
13.What Are The Advantages Of Hydrogen
Gas As Coolant Over Others?
Answer :
o
Density is 1/14 of air.
o
Windage loss is low.
o
Low noise.
o
Heat transfer co efficient is 1.5 times
higher than air.
o
Thermal conductivity is 7 times higher
than air.
14. What Are The Losses In A Generator?
Answer :
o
Stator copper
o
Stator iron
o
Rotor copper
o
Windage loss
o
Stray loss
o
Friction loss
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.
16.What Is The Value Of Scr In A 210 Mw
Turbo Alternator?
Answer :
SCR
= 0.49
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 overheating and damage.
18.What Type Of Protection Is Provided
For The Generators Against Over Heating Of The Generator Stator?
Answer :
Resistance
temperature detector.
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.
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.
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.
22.Why It Is Necessary To Suppress Field
Immediately After Disconnection Of Faulty Alternator From The System?
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.
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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