INDEX

Introduction 2

AC machines winding failure 3

AC 3-Phase Motor Protection 4

Current Transformer 5

Standby Diesel generator set 6

Generator Control panel 7

Contactors 8

Power transfering 8

Four Strock Diesel Engine 9

Injection Pump 10

Tappet clearance 11

Diesel engine’s posible Problems 12

Soundproofing 13

Passenger Elevator 14

Rope arangement methods 15

Lift motor 16

Governor 16

Ropes 17

Basic Logic Circuit of the Lift 17

1

INTRODUCTION

The Ceylon Electricity Board (CEB), is the largest electricity company in Sri

Lanka. It controls all major functions of electricity generation, transmission, distribution and

retailing in Sri Lanka. It is one of the only two on-grid electricity companies in the country; the

other being Lanka Electricity Company.

CEB Opened in 1969, the company now has a total installed capacity of 2,684 MW, of which

approximately 1,290 MW is from thermal energy, and 1,207 MW is from hydroelectricity. Due to

low wind resource, rough terrain and poor road conditions in Sri Lanka, CEB owns only one 3 MW

wind farm in Hambantota, known as the Hambantota Wind Farm. The farm consists of five

turbines, measuring 600 KW each. CEB also manages numerous hydroelectric dams such as the

Victoria Dam, and power plants such as the Norocholai Coal Power Station.

Hydroelectricity is the main source of energy in Sri Lanka, taking a share of nearly 45% of the total

installed capacity in December 2009. Currently, ten large hydroelectric power stations are in

operation, all between 38 to 210 MW, with the Victoria Dam being the largest hydroelectric source,

Thermal power stations are the largest source of power in Sri Lanka, taking a share of 48% of the

total installed capacity.

Also CEB conduct some other electrical services too. We were trained last period in some of those

workshops. In CEB we are trained by under the Electrical Superintend (ES) in that workshop. In

first two weeks in our training period we were in Aniyakanda Central Workshop. There were two

main workshops there.one is electrical workshop, another is electrical workshop. In electrical

workshop duty is about AC and DC machine, rewinding, repairing and maintained.

After that period we trained two weeks at Power plant section – Kolonnawa. In there mainly we

studied about large diesel power plants and about four stock engines. Then we trained at General

hospital lift branch. This branch also conduct by CEB. In there we studied about passenger lifts and

there maintainces.

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AC machines winding failure

A single phased winding failure is the result of an open in one of the phases that supply power to

the motor. The open is usually caused by a bad fuse, bad connection ,a open contactor or a broken

power line.

Thermal deterioration of insulation in one phase of the winding can result from unequal

voltage between phases. Unequal voltages usually are caused by unbalanced loads on the

power source, a poor connection at the motor terminal, or a high resistance contact. A one-

percent voltage unbalance can result in a six to ten percent current unbalance.

Thermal deterioration of the insulation in all phases of the stator winding typically is

caused by load demands exceeding the rating of the motor Under-voltage and over-voltage

will result in the same type of insulation deterioration.

Server thermal deterioration of the insulation in all phases of the motor normally is caused

by very high currents in the stator winding due to a locked rotor condition. It may also

occur as a result of excessive starts and reversals.

Insulation failures like this usually are caused by voltage surges. Voltage surges are often

the result of switching power circuits, lightning strikes, capacitor discharges and solid-state

power devices.

3

AC 3-Phase Motor Protection

Types of faults occurring within the protected zone requiring immediate tripping and

isolation of the motor are:

faults between stator windings

stator earth faults

Ground faults and faults between phases

The simple differential protection scheme:

The currents entering and leaving the equipment to be protected are stepped down with the help of

Current transformer’s on either side. For normal condition, the currents transformed by the C.T

being equal in phase and magnitude just circulate on the secondary side and there is spill current in

the over current relay. The over current relay is wired to trip the two circuit breakers on either side

of the equipment to be protected. A differential relay (over current relay) responds to the vector

difference between two or more similar electrical quantities. Thus the simple differential relay is

stable during normal operating condition.

Similarly during external fault condition, there is no difference in phase or magnitude of

the entering and leaving current thus giving a zero spill current. Thus the simple differential relay

is stable for the external fault condition also.

4

Current Transformer

A current transformer (CT) is used for measurement of electric currents. Current transformers,

together with voltage transformers (VT) (potential transformers (PT)), are known as instrument

transformers. When current in a circuit is too high to directly apply to measuring instruments, a

current transformer produces a reduced current accurately proportional to the current in the circuit,

which can be conveniently connected to measuring and recording instruments. A current

transformer also isolates the measuring instruments from what may be very high voltage in the

monitored circuit. Current transformers are commonly used in metering and protective relays in the

electrical power industry.

Like any other transformer, a current transformer has a primary winding, a magnetic core, and a

secondary winding. The alternating current flowing in the primary produces a magnetic field in the

core, which then induces a current in the secondary winding circuit. A primary objective of current

transformer design is to ensure that the primary and secondary circuits are efficiently coupled, so

that the secondary current bears an accurate relationship to the primary current.

The CT is typically described by its current ratio from primary to secondary. Often, multiple CTs

are installed as a "stack" for various uses. For example, protection devices and revenue metering

may use separate CTs to provide isolation between metering and protection circuits.

5

Standby Diesel generator set

In CEB standby diesel power generator supplies for some government institutes and various

occations.They have from 2KW smallest generators up to 1Mw huge Generators.

The packaged combination of a diesel engine, a generator and various ancillary devices such as

base, canopy, sound attenuation, control systems, circuit breakers, jacket water heaters, starting

systems etc, is referred to as a generating set or a gen set for short.

Set sizes range from 8 to 30 kVA for homes, small shops & offices with the larger industrial

generators up to 2,000 kVA used for large office complexes, factories. A 2,000 kVA set can be

housed in a 40ft ISO container and be fully packaged and portable. Sizes up to about 5 MW are

used for small power stations and these may use from one to 20 units. In these larger sizes the

engine and generator are brought to site separately and assembled along with ancillary equipment

Diesel generators, sometimes as small as 250 kVA are widely used not only for emergency power,

but also many have a secondary function of feeding power to utility grids either during peak

periods, or periods when there is a shortage of large power generators.

Types of Diesel Engines

There are two classes of diesel engines: two-stroke and four-stroke. Most diesel engines generally

use the four-stroke cycle, with some larger engines operating on the two-stroke cycle.  Normally,

banks of cylinders are used in multiples of two, though any number of cylinders can be used as

long as the load on the crankshaft is counterbalanced to prevent excessive vibration.

Generator sets produce either single or three phase power. Most homeowners require single phase

whereas industrial or commercial applications usually require three phase power. Diesel engine

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generators are recommended due to their longevity and lower operating costs. Modern diesel

engines are quiet and generally require much less maintenance than comparably sized gas (natural

gas or propane) units.

Generator Control panel features

AUTOMATIC MAINS FAILURE

ENGINE CONTROL

GENERATOR PROTECTION

BUILT IN ALARMS AND WARNING

3 PHASE MAIN VOLTAGE INPUTS

3 PHASE GENSET VOLTAGE INPUTS

ENGINE OIL PRESSURE MEASUREMENT

ENGINE COOLANT TEMP MEASUREMENT

GENSET ACTIVE POWER MEASUREMENT

GENSET POWER FACTOR MEASUREMENT

PERIODIC MAINTENANCE REQUEST INDICATOR

DAILY/WEEKLY/MONTHLY EXERCISER

STATISTICAL COUNTER

BATTERY BACKED-UP REAL TIME CLOCK

FIELD ADJUSTABLE PARAMETERS

LED DISPLAY

Power Transfering

For facilities with a standby power system and a single utility feed. The transfer switch senses

when utility power has been lost, sends a start signal to the standby generator and transfers the

load.High ampere rate contactors are used to make a contact lines

7

Contactors

Electrical relays and contactors are indispensable items when considering of using control circuits

in electrical installation work.Relays are used for low current consuming control apparatus and the

usage of contactors may vary from a few Amperes to thousands of Amperes in practical usage.

Contactors are mainly used to control machinery which uses electric motors.It consists of a coil

which connects to a voltage source. Very often for Single phase Motors , 230V coils are used and

for Three phase motors, 415V coils are used . The contactor has three main NO contacts and lesser

power rated contacts named as Auxiliary Contacts [NO and NC]used for the control circuit. A

contact is a conducting metal part which completes or interrupt an electrical circuit.

Consideration is given here on few basic usages of contactors, which can be made used in many

similar electrical power control applications.

When current passes through the electromagnet, a magnetic field is produced, which attracts the

moving core of the contactor. The electromagnet coil draws more current initially, until its

inductance increases when the metal core enters the coil. The moving contact is propelled by the

moving core; the force developed by the electromagnet holds the moving and fixed contacts

together. When the contactor coil is de-energized, gravity or a spring returns the electromagnet core

to its initial position and opens the contacts.

For contactors energized with alternating current, a small part of the core is surrounded with a

shading coil, which slightly delays the magnetic flux in the core. The effect is to average out the

alternating pull of the magnetic field and so prevent the core from buzzing at twice line frequency.

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Four Strock Diesel Engine

Four-stroke cycle

Intake stroke - On the intake or induction stroke of the piston , the piston descends from the

top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder.

A mixture of fuel and air is forced by atmospheric (or greater) pressure into the cylinder

through the intake port. The intake valve then close.

Compression stroke-With both intake and exhaust valves closed, the piston returns to the

top of the cylinder compressing the fuel-air mixture. This is known as the compression

stroke.

Power stroke- While the piston is close to Top Dead Center, the compressed air–fuel

mixture is ignited, usually by a spark plug (for a gasoline or Otto cycle engine) or by the

heat and pressure of compression (for a diesel cycle or compression ignition engine). The

resulting massive pressure from the combustion of the compressed fuel-air mixture drives

the piston back down toward bottom dead center with tremendous force. This is known as

the power stroke, which is the main source of the engine's torque and power.

Exhaust stroke- During the exhaust stroke, the piston once again returns to top dead center

while the exhaust valve is open. This action evacuates the products of combustion from the

cylinder by pushing the spent fuel-air mixture through the exhaust valves.

9

Injection pump

An Injection Pump is the device that pumps fuel into the cylinders of a diesel engine or less

typically, a gasoline engine. Traditionally, the pump is driven indirectly from the crankshaft by

gears, chains or a toothed belt (often the timing belt) that also drives the camshaft on overhead-

cam engines ( OHC ). It rotates at half crankshaft speed in a conventional four-stroke engine. Its

timing is such that the fuel is injected only very slightly before top dead centre of that cylinder's

compression stroke. It is also common for the pump belt on gasoline engines to be driven directly

from the camshaft.

Earlier diesel pumps used an in-line layout with a series of cam-operated injection cylinders in a

line, rather like a miniature inline engine. The pistons have a constant stroke volume, and injection

volume (ie, throttling) is controlled by rotating the cylinders against a cut-off port that aligns with a

helical slot in the cylinder. When all the cylinders are rotated at once, they simultaneously vary

their injection volume to produce more or less power from the engine. Inline pumps still find

favour on large multi-cylinder engines such as those on trucks, construction plant, static engines

and agricultural vehicles.

For use on cars and light trucks, the rotary pump or distributor pump was developed. It uses a

single injection cylinder driven from an axial cam plate, which injects into the individual fuel lines

via a rotary distribution valve. Later incarnations such as the Bosch VE pump vary the injection

timing with crank speed to allow greater power at high crank speeds, and smoother, more

economical running at slower revs. All injection pumps incorporate a governor to cut fuel supply if

the crank speed endangers the engine - the heavy moving parts of diesel engines do not tolerate

overspeeding well, and catastrophic damage can occur if they are over-revved

10

Tappet clearance

A tappet in mechanical engineering is a projection which imparts a linear motion to some other

component within an assembly. Properly speaking, a tappet is the only part of a rocker arm that

makes contact with an intake or exhaust valve stem above the cylinder head of an internal

combustion engine. As the cam rotates, it creates both a sideways and a downward force on the

tappet. Without a tappet (and with the cam acting directly on the valve), the sideways force would

cause the valve stem to bend. With a tappet, the sideways force is transferred to the cylinder head

so only the downward force acts on the valve stem.

On most modern overhead cam engines, the camshaft is directly over the valves, as pictured. In

some other overhead cam engines, a rocker arm pivots on a fixed shaft while one projection of the

rocker-arm rides on a cam of the rotating camshaft. In both cases, this creates an oscillating linear

motion, opening the valve. The closing of the valve is typically accomplished by a compression

spring placed between the valve collet (or retainer) and the cylinder head above the combustion

chamber. In overhead valve engines, the camshaft is located near the crankshaft and motion of the

cam lobes is followed by cam followers (similar to tappets) and transferred up to the cylinder head

and the rocker arm assembly by means of long pushrods.

Traditionally, the nominal distance (clearance) between the tappet surface and the valve's contact

surface was maintained by means of an adjustment screw on the rocker arm. Today, this is typically

accomplished by introducing shims into the space between the cam follower (tappet) and cam to

create the necessary clearance, or by hydraulic adjusters.

11

Diesel engine’s posible Problems

Low compression - Low engine compression will result in insufficient heat being

generated to ignite the fuel and cause hard starting. This is more of a problem with older or

high mileage vehicles. To find out the compression perform a cold engine compression

test. Compression should be between 20 to 35 bars or 300 to 500 PSI. Anything below this

will cause starting problems.

Insufficient fuel supply - This speaks for itself, not enough fuel in the tank or a problem

with supply pipes being cracked or bent. The fuel tank breather can sometimes be blocked

causing a vacuum in the tank which in turn draws the fuel back to the tank.

Air intake restriction - This would be due to a dirty air cleaner, blocked pipes or a stuck

butterfly valve found on some vehicles. In addition, a faulty air flow sensor on the air

intake will cause problems running and excessive smoke.

Black Smoke - This is due to a air to fuel ratio imbalance, either the fuel system is

delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few

things to look for :

Faulty injectors (injectors need attention at about 100.000 to 120 000 miles)

Faulty injector pump

Dirty air cleaner

Turbocharger or intercooler faulty

Problems within cylinder head, valves clogged up due to faulty EGR (exhaust gas

recycling unit

White Smoke - Normally means that the fuel injected into the cylinder is not burning

correctly. The smoke will burn your eyes.

Engine/pump timing out

Fuel starvation to the pump causing the pumps timing not to operate correctly

Low engine compression

Water/petrol in the fuel

12

Sound proofing

Sound proofing is any mechanism used to reduce the conduction of sound through a barrier or into

a soundproofed chamber. There are several different basic approaches to reducing sound;

increasing space in which the sound dissipates, using massive barriers to absorb the energy of the

sound waves, using dampening structures, or using active antinoise sound generators.

Dampening is the process by which sonic vibrations are converted into heat. This can be achieved

in several ways. For example, lead is both heavy and soft, with the softness allowing it to dampen

the noise rather than transmitting it through. Making a noise transfer through different layers of

material with different densities also helps dampen noise. This is the reason why open-celled foam

is such a good sound dampening substance; the sound waves are forced to travel through multiple

foam cells and foam cell walls as it passes through the foam piece. Improperly done, however,

dampening can make things worse — like the string holding chimes help them ring by isolating the

vibration instead of dampening it.

13

Passenger Elevator

A lift is essentially a platform that is either pulled or pushed up by a mechanical means. A modern

day lift consists of a cab (also called a "cage" or "car") mounted on a platform within an enclosed

space called a shaft or sometimes a "hoistway". In the past, lift drive mechanisms were powered by

steam and water hydraulic pistons. In a "traction" lift, cars are pulled up by means of rolling steel

ropes over a deeply grooved pulley, commonly called a sheave in the industry. The weight of the

car is balanced with a counterweight. Sometimes two lifts always move synchronously in opposite

directions, and they are each other's counterweight.

Geared traction machines are driven by AC or DC electric motors. Geared machines use worm

gears to control mechanical movement of elevator cars by "rolling" steel hoist ropes over a drive

sheave which is attached to a gearbox driven by a high speed motor. These machines are generally

the best option for basement or overhead traction use for speeds up to 500 ft/min.

14

Mainly there are two type rope arrangements

1 Lifting Drum arrangement

2 Traction Drum arrangement

15

Lift Motor

Normally three phase induction motor use as a lift Drive unit. It has a High speed and low speed

function. We can change the side of rotation of the motor by changing two supply phases of three.

Supply contacts control using contactors and relays. In modern lift’s they use microprocessor

control system and power electronic circuits for controlling motor speed and direction.

Gavernor

Gavernor is very important part of a lift. This is use as a safety equipment. Governor can detect

over speed of a lift and it gives signal to motor and also mechanical break. There are two main

break system of a lift. One is electrical breaking , another is mechanical breaking. There is a

maximum speed recommended for a lift, if that speed exceeds,(If ropes Breaks,motor falier….)

gavernor detect the problem and car comes immidiantly stop. Modern lifts has a electronis sensors

to detect the speed of the lift.

16

Elevator Ropes

No other application of steel wire ropes demands such close manufacturing tolerances and such

high quality in Materials as the elevator industry. No other industry demands such high safely

factors.These ropes are designed to satisfy most OEM specifications and are available for main

suspension, governor and compensating duties.

Basic Logic Circuit of the Lift

In passenger lift’s it want to good safety method. Therefore electric motor control unit want to

hoghly accepted signal for the motor running. There are various functions in lift..

Lift Door sensers

Position swiches

Floor doors sensors

Overload sensers

Buffer sensors

Emergency facts

Rope condition sensors..ect

Controling system use a AND operating method. If one of any facts have a problem the lift is not

running.

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