dg set.ppt

7/28/2019 DG SET.ppt

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INTERNAL COMBUSTON

ENGINES


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LECTURE PLAN

1. Introduction.

2. Classification of engines.

3. Diesel engine- Advantages, differences.

4. D.G.Set.

5. Diesel engine, main parts, functions.

6. Four strokes in diesel engine.

7. Systems in Diesel engine.

8. Starting methods of Diesel engine.


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9. Routine maintenance

10. Attending problems in Diesel engine.11. Ds & Dons.

12. Spares & Consumables.

13. Tools for maintenance.

14. Alternator & Principle of operation.

15. Types of alternator

16. Parts of alternator.

17. Dos & Donts.


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INTERNAL COMBUSTON

ENGINES

Internal combustion engines are those inwhich Combustion takes placeinternally in the cylinder of the engine.

These are TWO types,1. Petrol engines takes petrol as fuel

2. Diesel engines takes Diesel as fuel

In the above Diesel engines are used inDiesel generator set


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CLASSIFICATION DEPENDING

ON NUMBER OF STROKES

Depending on number of strokes in

(stroke means movement of piston either

TDC to BDC or BDC to TDC) the above

two can be divided into,

1. TWO stroke engine.

2. FOUR stroke engine.


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DIESEL ENGINE


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ADVANTAGE OF DIESEL ENGINE

1. Cost of fuel is cheap

2. Suitable for heavy vehicles

3. Injector in Diesel engine is rarely gets defective

4. Initial torque is high

5. Its maintenance cost is less

6. The period of overhauling is large

7. Due to high compression ratio, efficiency is high

8. Fuel is non-explosive

Due to above Diesel engine is preferred for DG set


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DIFFERENCES

DIESEL ENGINE

1. Air only compressed

2. Compression ignition

3. No carburetor4. Diesel evaporates

slowly

5. Density is higher

6. Diesel contains147000 btu/gallon

(3.8 Ltrs)

PETROL ENGINE

1. Mixture of air& petrol is

compressed

2.Spark ignition3. Carburetor is provided

4. Evaporation is quick

5. Density is low

6.Petrol contains 125000btu / gallon (3.8 Ltrs)


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DIESEL GENERATOR SET


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DIESEL GENERATOR SET

The DG set consists of Diesel engine and

Alternator joined through coupling.


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SIMPLE DIESEL ENGINE

It is one type of IC

engine uses Diesel fuel

It converts Fuel energy

into Mechanical energy.

A simple Diesel engine

consists of

1. Cylinder

2. Piston3. Two valves

4. Fuel injector


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MAIN PARTS OF DIESEL

ENGINE1. Cylinder

2. Piston and piston rings

3. Connecting rod

4. Crank shaft5. Cam shaft

6. Fly wheel

7. Oil sump

8. Valves (i) Inlet valve (ii) Exhaust valve9. Fuel injector

10. Fuel tank


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CYLINDER OF THE ENGINE

The cylinder is the place where the combustiontakes place and it also serves as bearing andguides for the piston reciprocating in it.

Around the cylinder there is a passage for thecirculation of cooling water.

At the top of the cylinder is attached the cylinderhead which houses the valves and fuel injector.

The cylinder and its head are separated by agasket, which prevents the leakage of air andgases from the cylinder to the atmosphere.


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PISTON AND PISTON RINGS

It is cylindrical inshape and movesinside the cylinder.

It is connected to theconnecting rodthrough Gudgeonpin.

Piston rings areprovided on its topouter surface.


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CONNECTING ROD

It connects piston to the

crank shaft. Gudgeon pin

is used to connect with

piston.

Small bearing end is

connected to piston and

large bearing end is

connected to crank shaft.

It transmits the motion ofthe piston to the crank

shaft.


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CRANK SHAFT


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The crankshaft is located inside the

crankcase. The bottom end of the connecting rod is

connected to crankshaft.

It receives the linear motion from theconnecting rod and converts it to rotary

motion by virtue of its construction.


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FLY WHEEL

The flywheel is connected at the rear end of thecrankshaft.

It serves as a reservoir of energy.

As there is only one working stroke in two revolutions of

the crankshaft, the flywheel absorbs the excess energyduring the power stroke and gives out the absorbedenergy during the other three strokes.

Thus it is the flywheel, which keeps the crankshaftrotating at the uniform speed throughout.

The flywheel has teeth on its outer periphery, whichmesh with the pinion of the starter motor to start theengine.


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OIL SUMP

The lubricating oil sump is located at the

bottom of the crankcase and surrounds

the crankshaft. It contains some amount of

lubricating oil, which collects at the bottomof the sump.

Oil is supplied to all the moving parts of

the engine by the oil pump that is locatedin the sump.


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VALVES

Inlet valve: This is

located in the cylinder

head and opens into

the cylinder against

the spring tension toallow the atmospheric

air into the cylinder

during intake stroke.

This is operated bythe rocker arm

through push rod and

cam of the camshaft.

Exhaust valve: Itopens during exhaust

stroke against the

spring tension to let

the burnt gases into

the atmosphere

through the exhaust

pipe.


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FUEL INJECTOR

It receives the high-

pressure fuel from the

fuel injection pump

(plunger pump) andsprays into the

cylinder in misty form

through nozzle, when

the piston is at TDCduring compression

stroke.


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STROKES IN DIESEL ENGINE


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STROKE 1: INTAKE STROKE

STROKE 2: COMPRESSION STROKE

STROKE 3: POWER STROKE STROKE 4: EXHAUST STROKE

The Four-Stroke Diesel Engine


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FOUR STROKES IN DISEL

ENGINE


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During the intake strokethe inlet valve is openedand the outlet valve isclosed

The piston movesdownward towards BDC.

The pressure drops in thecylinder and because ofthe low pressure the air

from the atmosphere issucked into the cylinder.

STROKE 1: INTAKE STROKE


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STROKE 2: COMPRESSION

STROKE

The inlet valvecloses and thecylinder is filled

with air. The outletvalve remains inclosed condition.


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Piston moves upward to the TDC

and compresses the air. Thepressure in the cylinder

increases, the volume decreases

and the temperature increases.

The temperature of compressed

air goes up to 400C to 700C .


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STROKE 3:POWER STROKE

The diesel is

injected or sprayed

into the cylinder in

misty form underhigh pressure at the

end of the

compression stroke.


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STROKE 3:POWER STROKE

The temperature of the air inside the cylinderis high enough to ignite the fuel andcombustion takes place.

The heat energy developed inside the

cylinder due to combustion leads to theexpansion of burnt gases and increase inpressure.

The high pressure of the burnt gases forces

the piston to BDC. In this stroke both the valves remain inclosed condition.


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STROKE 4: EXHAUST STROKE

The piston whichis at BDC, aftercompletion ofpower stroke,starts moving toTDC and theexhaust valveopens.


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STROKE 4: EXHAUST STROKE

The burnt gases discharge to theatmosphere under the upward thrust of thepiston through the exhaust valve.

The inlet valve remains in closed condition

during this stroke. The piston reaches to TDC and will be ready

for the next cycle of operation.

These four strokes produce two revolutions

of the crankshaft. This process, continuously, repeats itself

during the operation of the engine.


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FOUR STROKES:OPERATION


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DIESEL CYCLE


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SYSTEMS IN DIESEL ENGINE

The diesel engine is mainly divided into four

systems in terms of regular maintenance, which

require frequent attention.

They are,1. Fuel system

2. Lubricating system.

3. Cooling system.4. Starting system- hand and electric.


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FUEL SYSTEM

This system pressurizes and injects the fuel.

In this way the fuel is forced into air, which has beencompressed to high pressure in the combustionchamber.

The diesel fuel injection system consists of a fuelinjection pump, an injection nozzle, a feed pump, a fuelfilter and a high-pressure pipe.

The fuel injection pump pressurizes fuel to high pressureand then sends it via the high-pressure pipe to theinjection nozzle, which injects the fuel into the cylinder.

The feed pump sucks the fuel from the fuel tank and thefuel filter of course filtrates the fuel.


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FUEL INJECTION SYSTEM


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FUNCTIONS OF THE SYSTEM

The fuel injection system has

four functions:

1. Feeding the fuel,2. Adjusting the fuel quantity,

3. Adjusting injection timing and4. Atomizing the fuel.


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LUBRICATING SYSTEM

Function:- To reduce the heat caused byfriction.

All moving parts are lubricated.

The lubricating system consists of:-

a) Oil sump.b) Oil pump .

c) Relief valve.

d) Oil filter.

e) Lubricating oil.


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LUBRICATING SYSTEM


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COOLING SYSTEM

FUNCTIONS:-

1. To cool the engine,

2. To ensure that the working temperature

of the engine is maintained within limits. TYPES:-

a) Air cooling.

b) Water cooling.


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AIR COOLING

Effective cooling

surface area is

increased by

providing fins over thecylinder.

Air is blown on the

fins by a fan to cool

the engine,


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WATER-COOLING SYSTEM

A centrifugal water

pump mounted on the

engine and driven by

a vee belt driven fromthe crankshaft. The

water pump pulley

has a provision for

mounting the fan.


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The water is drawn from the bottom of the

tank by the water- circulating pump. Thecooling water then passes through theengine jackets, absorbs the heat of theengine and gets hot.

The hot water enters the top of the radiatorand passes through the finned tubes to thebottom.

An airflow provided by the fan cools thewater by absorbing the heat as it passesthrough the tubes.


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STARTING SYSTEM

This is TWO types:

1. Hand starting.

2. Electrical starting.

HAND STARTING:

1.Move the speed control lever to the full

speed position.2.Check the stop/start lever in starting

position.


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HAND STARTING

3.Move the decompressor lever to the startposition.

4.Using starting handle rotate the engine briskly.

5.When engine is running freely at sufficient

speed, move the decompressor lever to therun position. During this operation, continuerotating the engine.

6. When the engine fires and is accelerating,

withdraw the starting handle. Do not releasehold of the handle before withdrawing it from theshaft.


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ELECRTICAL STARTING

PROCEDURE OF ELECRTICAL


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PROCEDURE OF ELECRTICAL

STARTING

1. Move the speed control lever over the full speedposition.

2. Check the engine stop/start lever in startposition.

3. Move the de compressor lever to the RUNposition.

4. Press the starter button until engine fires.

5. If the engine does not fire at once, allow it to

come to rest before pressing the starter. NOTE: DONOT OPERATE THE STARTER

WHILE THE ENGINE IS RUNNING.


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RUNNING

Immediately after the engine starts, check

the lubricating oil pressure. This should be

between 35/45 lb/sq.in.

Run the engine for a few minutes in order

to warm up before applying the load.

The load should be applied gradually

whenever possible.


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STOPPING

1. It is preferable to remove the load and allow the

engine to run light for a short period.

2. Move and hold the engine stop/start lever in the

stop position until the engine stops.(Warning): on no account must the de

compressor lever be used to stop the engine as

this may result in severe damage to the valve

gear).3. Clean down the engine whilst it is still warm.


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ROUTINE MAINTENANCE

Daily - before starting1.Check level of fuel in service tank. The tank

should be full with clean fuel at the end of daysof work.

2.Checl level of lubricating oil in sump. Top it ifnecessary.

3.Check level of water in radiator and top up ifnecessary, before stating the engine.

4.Clean the engine at the end of days work. If anyleakages are there, should be attendedimmediately.


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OCCASIONALLY

5.Lubricate the links and connections of all

external controls.

6.check grease on any auxiliary equipment.

7.Check the tension of the driving belt for

the water pump and radiator fan.


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HOURLY MAINTAINCE

Every 50 hours of run:

8.Clean the oil bath air filter and top with oil to the

marked level.

Every 250 hours of run:9.Inspect fuel filter element. Renew if necessary.

10.Renew lubricating oil filament.

11.Drain lubricating oil sump and refill with new oil.12.Check the corrosion plugs (heater) and replace

them if necessary.


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13. Inspect fuel filter element. Renew ifnecessary.

14. Clean lubricating oil filler gauze andcrankcase breather.


15.Remove injectors, clean injector filter andtest spray. Replace without interference if

spray is satisfactory.16.Renew fuel filter elements.


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EVERY 1500 HOURS OF RUN

17.If engine shows loss of power, remove

cylinder and examine valves, grind in if

necessary. Examine piston and check

wear with recommended maximum wearallowances.

18.Inspect complete cooling system i.e.

clean and flush cooling system and cleanthe vent hole in thermostat valve.


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19.Remove cylinder heads, examine the inlet andexhaust valves, decarbonize and grind in valves.

20.Withdraw and clean pistons, check that ringsare free and the wear is within therecommended tolerance.

21.Check and adjust valve and fuel pump tappetclearances.

22.Examine large end bearings and checkcrankpins for ovality and scoring.

23.Clean exhaust port, pipes and silencer.

ENGINE OVERHAUL

EVERY 3000 HOURS


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EVERY 6000 HOURS

24.Examine bearings and check crankshaft

for ovality and scoring.

25.Flush out all fuel and lubricating oil pipes.

26.Remove and examine lubricating oil

pump.

27.Renew connecting rod bolts.

PROBLEMS IN GENERAL


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PROBLEMS IN GENERAL

1. Air lock in fuel system:

Air lock is nothing but entry of air into

the fuel system whenever the fuel

filters are opened for cleaning and forreplacement or whenever the fuel tank

gets empty or due to lose fuel delivery

pipes connections. This air enters intothe fuel injection pump.

PROCEDURE TO REMOVE


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PROCEDURE TO REMOVE

AIR LOCK

a.First fill the diesel tank with diesel if fuel is foundless.

b. Unscrew the fuel feed pump and operate it tillthe pressure is built up.

c. Screw out the air bleeding screws and operatethe pump till the air from the filter bowls comesout. Then close the fuel bleeding screws andtighten the fuel feed pumps knob.

d. Crank the engine and make sure that the air isbled out of FIP by opening the high pressurepipes near the injectors and tighten them whenthe air is totally bled out of the fuel system.


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NOZZLE CHOKING

e. Clean the diesel at all joints and on pipesbefore starting. Start the DG set and run itfor sometime to ensure that the fuel

system is free from air.2. Nozzle choking:a. Disconnect the nozzle from cylinder head.

b. Turn the nozzle to opposite direction then hand

crank the engine. Diesel should come out asspray otherwise nozzle is choked.

c. Clean the nozzle by very thin pin, it will open.


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DOS ANDDONS


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DOS

Dos

Ensure proper cleaning of air cleaner and fuelfilter.

Before starting ensue that the fuel tank is full. Connect the load only when generator voltageregulation is normal.

Before starting the DG open doors for proper

ventilation. Run DG without load for few minutes before

stopping.

Carry out the daily and periodic maintenance.

Make sure that load current is within limits.


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Donts Dont mix water with fuel. Dont mix different grades of grease.

Dont pour diesel when running.

Dont start the engine without checking thelubricating oil.

Dont start the engine without opening fuel taps.

Dont start the engine with load. First start theengine and allow it to gain full speed before

putting the load on. Dont smoke in the DG room and also dont keep

inflammable goods in DG room.


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SPARES AND CONSUMABLES

1. Fuel filter - 2nos2. Oil filter - 2nos

3. Fuel pipe - 2sets

4. Pressure pipe - 1no

5. Air cleaner - 1no6. Nozzle - 2nos

7. Ring set - 1no

8. Fan belt - 2nos

9. Grease

10. Lubricating oil

11. Cotton waste.


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TOOLS FOR MAINTENANCE

1.spanners (set & ring)

2.Cutting pliers

3.Nose pliers

4.screw driver 6"

5.screw driver 12"

6.Feeler gauge

7.Mallet

8. Box spanner set.


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ALTERNATOR


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INTRODUCTION

Alternator is an AC generator which works

on principle of Electromagnetic induction.

It says that whenever a conductor cuts the

magnetic flux, an e.m.f. is always inducedin it.

PRINCIPLE OF OPERATION OF


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PRINCIPLE OF OPERATION OF

AN ALTERNATOR


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The operation of an AC generator(alternator) can be explained by a simpleloop of wire placed between the poles of apermanent magnet and made to rotate.

As the loop rotates, it passes through, or

cuts, the magnetic lines of force, and avoltage is developed in it. In a practicalgenerator, actually a series of largenumber of such loops contained in a rotor

or an armature produces e.m.f. largeenough to be practically useful.


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Thus produced voltage is connected to the

external circuit through slip rings and

brushes.

The slip ring rotate as the loop rotates and

the brushes dont move but only stay in

contact with the rings by sliding along their

surface as they rotate.

GENERATING A SINE WAVE


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GENERATING A SINE WAVE

OUTPUT


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So for one full rotation, the generatedvoltage corresponds to 360 electrical

degrees. Thus for a simple two-pole generator, one

cycle of the sine wave output is generated

each time the loop makes one full rotation. The frequency of such a generator is the

same as the speed of rotation of the loop.

The magnitude of the peak voltageincreases with increase in the rate ofchange of flux linkage of the coil.


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TYPES OF ALTERNATORS


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The types of alternators are configured uponrelative motion between an electric conductor

and magnetic field. The relative motion can bebrought in three ways.

By moving conductors through a stationarymagnetic field, as in the rotating armaturealternator.

BY moving a magnetic field across stationaryconductors as in the rotating field armature.

By varying the intensity of the magnetic fieldsurrounding stationary conductors as in the

inductor alternator.

RELATION BETWEEN


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FREQUENCY, SPEED AND

POLES IN AN ALTERNATOR

f =2N/60

Let P= total number of magnetic poles

N=rotative speed of the rotor in r.p.m. F= frequency of generated e.m.f. in c/s.

Since one cycle of e.m.f is produced when apair

of poles passes past a conductor, the number ofcycles of e.m.f. produced in one revolution of the

rotor is equal to the number of pair of poles.


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No. of cycles per revolution = P/2

No. of revolutions/ Sec =N/60

P N PN

frequency = ---- X ----- = ----- c/s2 60 60

PN

or f = ------ c/s

120

S O O S


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TYPES OF ALTERNATORS

The types of alternators are configured uponrelative motion between an electric conductorand magnetic field. The relative motion can bebrought in three ways.

1. By moving conductors through a stationarymagnetic field, as in the rotating armaturealternator.

2. BY moving a magnetic field across stationaryconductors as in the rotating field armature.

3. By varying the intensity of the magnetic fieldsurrounding stationary conductors as in theinductor alternator.


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PARTS OF ALTERNATOR

PARTS OF ALTERNATOR


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PARTS OF ALTERNATOR

1. Shaft of Armature2. Slip rings

3. Brush assembly.

4. Pole Pieces5. Rectifier set

6. Stator & Field coils

7. Armature coils8. Terminal box

SHAFT


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SHAFT

It is usually made of cast iron or caststeel and has a heavy central hub, a

number of radial arms, and a heavy rim

that forms the yoke of the magnetsystems.

ARMATURE COILS


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ARMATURE COILS

The copper conductor with high qualityof insulation are wounded over the

armature of several turns to produce

sufficient quantity of electricity when itis rotating with in the electro magnetic

field at a certain speed

SLIP RINGS


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SLIP RINGS

Two rings made from the copper areassembled on the armature, separated

from the body of the armature with

insulator and the ends of the conductorsare connected on it.

BRUSH ASSEMBLY


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BRUSH ASSEMBLY

It is made from carbon and remains

attached with the slip ring with the carbon

holder assembly to bring out thegenerated voltages at the out side of the

armature.

POLE PIECES


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POLE PIECES

The soft iron core has the soft iron pole

pieces to give low reactance path to the

magnetic flux.

RECTIFIER SET


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RECTIFIER SET

The rectifiers unit is incorporated with thegenerator to rectify the generated output & togive supply to the self excited electromagnetic

field of the stator. The unit has a full waverectifier.

The input of this bridge rectifier is given from theoutput of the generator through the adjustable

field rheostat housed in the termination box toprovide the excitation current to the field coil forsufficient field strength.

THE STATOR


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THE STATOR

It consists of an outer frame, the field pole,and field coil, which serve as

electromagnet.

The field coils are wounded on the polepieces and they may be energized from an

external DC source (separate excitation)

or self-excitation, here field winding isexcited by its own armature winding.

ROTOR


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ROTOR

The rotating part of the alternator is therotor, which is laminated and

accommodates the generator winding in

its slots on the outer surface. The windingsare terminated on slip rings. When an

external load is not connected to the slip

rings, the windings will be as an opencircuit and if an external load is connected

it is said to be a closed circuit.

COIL GROUPS IN ARMATURE


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COIL GROUPS IN ARMATURE

The grouping of coils in an armature ofalternator is to produce a.c output. The

direction of the induced emf is upwards at

right angle to the plane of the paper canbe determined as right hand rule and is

shown in fig by black dots.

MAINTENANCE


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MAINTENANCE

General: The alternator should be stoppedand isolated from all supplies before

carrying out any maintenance on electrical

or rotating parts. It should be done asfollows-


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1) Cleaning: The generator and excitation

unit should be periodically cleaned

internally by blowing out with a jet of dry

air and by wiping away any deposits of

grease and carbon dust with a clean dry

cloth .All nuts and screws should bechecked to ensure that they are tight,

especially the electrical connections.


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2) Brushes: The brushes should beexamined initially after every 100 hours of

running to see that they are beddedproperly and are also not sticking to theirholders. The brushes should be checked

for correct pressure and it should bebetween 200 to 250 g/cm2. (Refer toinstruction manual) and should bereplaced before they are worn out to the

minimum permissible length.


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3) Slip rings:

Periodical inspection of slip rings and the

spaces between the rings should be cleaned. Ifthere is any sign of blackening on the surfacesof the rings, the brush pressure should bechecked and readjusted .If badly blackened,the rings should be polished.

If pronounced flats have developed the ringsmust be skimmed and polished and thebrushes should be rebedded. Then clean themachine by a jet of dry air and polish before it

is put back into service.


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4) Bearings:

Ball and roller bearings will run for longperiods without any attention as the

bearing housings are charged with right

quality and quantity of grease. Additional

grease is not required to be used untilafter each period of 2000 to 3000 hours of

running.

Lithium base grease conforming to grade3 of IS:1002-1956 is recommended.


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TROUBLE SHOOTING


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No voltage from generator

It may arise due to the following reasons:1. Wrong field connection.

2. Open circuit in field winding

3. Loss of residual magnetism4. Faulty rectifier.

5. Brushes not bedded properly.

6. Short-circuit or open circuit in armature

winding.


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Low or High voltage from generator

on no load -It may be due to:

1. Incorrect speed of prime mover.

2. Rectifier faulty.

3. Turns shorted in one of the field coils.


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Voltage Regulation is unsatisfactory

1) Incorrect speed of the prime mover2) Over load

3) Low power factor of the connected load.


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DosandDonts


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Dos

1.Keep the machine clean and dry, theexposed parts have to be protected byapplying paint or antirust coating.

2.The frame of the machine should beearthed.

3.Connect the load only when generator

voltage regulation is normal.4.Make sure that load current is within limits.

Dos


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5. Ensure that proper Overload and shortcircuit protection system are installed.

6. Check any overheating of any parts

during running.

7. Check for any unusual sound during

running.

8. Carry out the daily and periodicmaintenance

Donts


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Don ts

Donts1) Dont install the machine where

ventilation is poor.

2) Dont mount the machine in any otherposition other than horizontal one unlessspecifically approved.

3) Dont start the engine with load. First startthe engine and allow it to gain full speedbefore putting the load on.

SPARES


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Recommended spares are:

1. One set of brush.

2. One set of bearing.

3. One set of rectifier.

dg set.ppt

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