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Our Lady of Manaoag College

Bachelor of Science in Computer Science (BSCS-I)

Research Work inPhysics II

(Heat, Electricity & Magnetism)

Jommel Ryan J. Flores

BSCS-I2

ndsem. sy: 2012-2013

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How Electric Motor Operate

An electric motor is anelectric machinethat convertselectrical energy into mechanicalenergy.

In normal motoring mode, most electric motors operate through the interaction between an electric

motor'smagnetic fieldandwinding currentsto generate force within the motor. In certain applications,

such as in the transportation industry withtraction motors, electric motors can operate in both

motoring andgenerating or brakingmodes to also produce electrical energy from mechanical energy.Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household

appliances, power tools, and disk drives, electric motors can be powered bydirect current (DC)sources,

such as from batteries, motor vehicles or rectifiers, or byalternating current (AC)sources, such as from

the power grid,invertersor generators. Small motors may be found in electric watches. General-

purpose motors with highly standardized dimensions and characteristics provide convenient mechanical

power for industrial use. The largest of electric motors are used for ship propulsion, pipeline

compression andpumped-storageapplications with ratings approaching a megawatt. Electric motors

may be classified by electric power source type, internal construction, application, type of motion

output, and so on.

Devices such as magnetic solenoids and loudspeakers that convert electricity into motion but do not

generate usable mechanical power are respectively referred to as actuators and transducers. Electric

motors are used to produce rotary or linear torque or force.

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Success with DC motors

The first commutator DC electric motor capable of turning machinery was invented by the British

scientist William Sturgeon in 1832.Following Sturgeon's work, a commutator-type direct-current electric

motor made with the intention of commercial use was built by the American inventor Thomas

Davenport, which he patented in 1837. The motors ran at up to 600 revolutions per minute and

powered machine tools and a printing press. Due to the high cost of primary battery power, the motors

were commercially unsuccessful and Davenport went bankrupt. Several inventors followed Sturgeon in

the development of DC motors but all encountered the same battery power cost issues. No electricity

distribution had been developed at the time. Like Sturgeon's motor, there was no practical commercial

market for these motors.

In 1855 Jedlik built a device using similar principles to those used in his electromagnetic self-rotors that

was capable of useful work.] He built a model electric vehicle that same year.

The first commercially successful DC motors followed the invention by Znobe Gramme who had in 1871

developed the anchor ring dynamo which solved the double-T armature pulsating DC problem. In 1873,

Gramme found that this dynamo could be used as a motor, which he demonstrated to great effect at

exhibitions in Vienna and Philadelphia by connecting two such DC motors at a distance of up to 2 km

away from each other, one as a generator. (See also 1873: l'exprience decisive [Decisive Workaround].)

In 1886 Frank Julian Sprague invented the first practical DC motor, a non-sparking motor that

maintained relatively constant speed under variable loads. Other Sprague electric inventions about this

time greatly improved grid electric distribution (prior work done while employed by Thomas Edison),

allowed power from electric motors to be returned to the electric grid, provided for electric distribution

to trolleys via overhead wires and the trolley pole, and provided controls systems for electric operations.This allowed Sprague to use electric motors to invent the first electric trolley system in 188788 in

Richmond VA, the electric elevator and control system in 1892, and the electric subway with

independently powered centrally controlled cars, which were first installed in 1892 in Chicago by the

South Side Elevated Railway where it became popularly known as the "L". Sprague's motor and related

inventions led to an explosion of interest and use in electric motors for industry, while almost

simultaneously another great inventor was developing its primary competitor, which would become

much more widespread. The development of electric motors of acceptable efficiency was delayed for

several decades by failure to recognize the extreme importance of a relatively small air gap between

rotor and stator. Efficient designs have a comparatively small air gap. [a] The St. Louis motor, long used

in classrooms to illustrate motor principles, is extremely inefficient for the same reason, as well as

appearing nothing like a modern motor.Application of electric motors revolutionized industry. Industrial processes were no longer limited by

power transmission using line shafts, belts, compressed air or hydraulic pressure. Instead every machine

could be equipped with its own electric motor, providing easy control at the point of use, and improving

power transmission efficiency. Electric motors applied in agriculture eliminated human and animal

muscle power from such tasks as handling grain or pumping water. Household uses of electric motors

reduced heavy labor in the home and made higher standards of convenience, comfort and safety

possible. Today, electric motors stand for more than half of the electric energy consumption in the US.

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Emergence of AC motors

In 1824, the French physicist Franois Arago formulated the existence of rotating magnetic fields,

termed Arago's rotations, which, by manually turning switches on and off, Walter Baily demonstrated in

1879 as in effect the first primitive induction motorIn the 1880s, many inventors were trying to develop

workable AC motors because AC's advantages in long distance high voltage transmission were

counterbalanced by the inability to operate motors on AC. Practical rotating AC induction motors were

independently invented by Galileo Ferraris and Nikola Tesla, a working motor model having been

demonstrated by the former in 1885 and by the latter in 1887. In 1888, the Royal Academy of Science of

Turin published Ferraris research detailing the foundations of motor operation while however

concluding that "the apparatus based on that principle could not be of any commercial importance as

motor. In 1888, Tesla presented his paper A New System for Alternating Current Motors and

Transformers to the AIEE that described three patented two-phase four-stator-pole motor types: one

with a four-pole rotor forming a non-self-starting reluctance motor, another with a wound rotor forming

a self-starting induction motor, and the third a true synchronous motor with separately-excited DC

supply to rotor winding. One of the patents Tesla filed in 1887, however, also described a shorted-

winding-rotor induction motor. George Westinghouse promptly bought Teslas patents, employed Tesla

to develop them, and assigned C. F. Scott to help Tesla, Tesla leaving for other pursuits in 1889 Theconstant speed AC induction motor was found not to be suitable for street cars but Westinghouse

engineers successfully adapted it to power a mining operation in Telluride, Colorado in 1891.Steadfast in

his promotion of three-phase development, Mikhail Dolivo-Dobrovolsky invented the three-phase cage-

rotor induction motor in 1889 and the three-limb transformer in 1890. This type of motor is now used

for the vast majority of commercial applications. However, he claimed that Tesla's motor was not

practical because of two-phase pulsations, which prompted him to persist in his three-phase work.

Although Westinghouse achieved its first practical induction motor in 1892 and developed a line of

polyphase 60 hertz induction motors in 1893, these early Westinghouse motors were two-phase motors

with wound rotors until B. G. Lamme developed a rotating bar winding rotor. The General Electric

Company began developing three-phase induction motors in 1891. By 1896, General Electric and

Westinghouse signed a cross-licensing agreement for the bar-winding-rotor design, later called thesquirrel-cage rotor. Induction motor improvements flowing from these inventions and innovations were

such that a 100 horsepower (HP) induction motor currently has the same mounting dimensions as a 7.5

HP motor in 1897.

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How Generators OperateAn electric generator is a device that converts mechanical energy obtained from an externalsource into electrical energy as the output.

It is important to understand that a generator does not actually create electrical energy. Instead,it uses the mechanical energy supplied to it to force the movement of electric charges present in

the wire of its windings through an external electric circuit. This flow of electric charges

constitutes the output electric current supplied by the generator. This mechanism can be

understood by considering the generator to be analogous to a water pump, which causes the flow

of water but does not actually create the water flowing through it.

The modern-day generator works on the principle of electromagnetic induction discovered by

Michael Faraday in 1831-32. Faraday discovered that the above flow of electric charges could be

induced by moving an electrical conductor, such as a wire that contains electric charges, in a

magnetic field. This movement creates a voltage difference between the two ends of the wire orelectrical conductor, which in turn causes the electric charges to flow, thus generating electric

current.

Main components of a generatorThe main components of an electric generator can be broadly classified as follows (refer toillustration above):

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(1) Engine

(2) Alternator

(3) Fuel System

(4) Voltage Regulator

(5) Cooling and Exhaust Systems

(6) Lubrication System(7) Battery Charger

(8) Control Panel

(9) Main Assembly / Frame

A description of the main components of a generator is given below.

(1) EngineThe engine is the source of the input mechanical energy to thegenerator. The size of the engine is directly proportional to the

maximum power output the generator can supply. There are several

factors that you need to keep in mind while assessing the engine of yourgenerator. The manufacturer of the engine should be consulted to obtain

full engine operation specifications and maintenance schedules.

(a) Type of Fuel UsedGenerator engines operate on a variety of fuels such as diesel, gasoline,

propane (in liquefied or gaseous form), or natural gas. Smaller engines usually operate on

gasoline while larger engines run on diesel, liquid propane, propane gas, or natural gas. Certainengines can also operate on a dual feed of both diesel and gas in a bi-fuel operation mode.

(b) Overhead Valve (OHV) Engines versus non-OHV EnginesOHV engines differ from other

engines in that the intake and exhaust valves of the engine are located in the head of the enginescylinder as opposed to being mounted on the engine block. OHV engines have several

advantages over other engines such as:

Compact design

Simpler operation mechanism

Durability User-friendly in operations

Low noise during operations

Low emission levels

However, OHV-engines are also more expensive than other engines.

(c) Cast Iron Sleeve (CIS) in Engine CylinderThe CIS is a lining in the cylinder of the engine.It reduces wear and tear, and ensures durability of the engine. Most OHV-engines are equipped

with CIS but it is essential to check for this feature in the engine of a generator. The CIS is not an

expensive feature but it plays an important role in engine durability especially if you need to useyour generator often or for long durations.

(2) Alternator

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The alternator, also known as the genhead, is the part of the generator that produces the

electrical output from the mechanical input supplied by the engine. It contains an assembly of

stationary and moving parts encased in a housing. The components work together to causerelative movement between the magnetic and electric fields, which in turn generates electricity.

(a) StatorThis is the stationary component. It contains a set of electrical conductors wound incoils over an iron core.

(b) Rotor / ArmatureThis is the moving component that produces a rotating magnetic field in

any one of the following three ways:

(i) By inductionThese are known as brushless alternators and are usually used in large

generators.(ii) By permanent magnetsThis is common in small alternator units.

(iii) By using an exciterAn exciter is a small source of direct current (DC) that energizes the

rotor through an assembly of conducting slip rings and brushes.

The rotor generates a moving magnetic field around the stator, which induces a voltage

difference between the windings of the stator. This produces the alternating current (AC) outputof the generator.

The following are the factors that you need to keep in mind while assessing the alternator of agenerator:

(a) Metal versus Plastic HousingAn all-metal design ensures durability of the alternator.Plastic housings get deformed with time and cause the moving parts of the alternator to be

exposed. This increases wear and tear and more importantly, is hazardous to the user.

(b) Ball Bearings versus Needle BearingsBall bearings are preferred and last longer.

(c) Brushless DesignAn alternator that does not use brushes requires less maintenance and also

produces cleaner power.

(3) Fuel SystemThe fuel tank usually has sufficient capacity to keep the generator

operational for 6 to 8 hours on an average. In the case of small

generator units, the fuel tank is a part of the generators skid base or ismounted on top of the generator frame. For commercial applications, it

may be necessary to erect and install an external fuel tank. All such

installations are subject to the approval of the City Planning Division.

Click the following link for further details regardingfuel tanks for generators.

Common features of the fuel system include the following:

(a) Pipe connection from fuel tank to engineThe supply line directs fuel from the tank to the

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engine and the return line directs fuel from the engine to the tank.

(b) Ventilation pipe for fuel tankThe fuel tank has a ventilation pipe to prevent the build-up ofpressure or vacuum during refilling and drainage of the tank. When you refill the fuel tank,

ensure metal-to-metal contact between the filler nozzle and the fuel tank to avoid sparks.

(c) Overflow connection from fuel tank to the drain pipeThis is required so that any overflowduring refilling of the tank does not cause spillage of the liquid on the generator set.

(d) Fuel pumpThis transfers fuel from the main storage tank to the day tank. The fuel pump istypically electrically operated.

(e) Fuel Water Separator / Fuel FilterThis separates water and foreign matter from the liquid

fuel to protect other components of the generator from corrosion and contamination.

(f) Fuel InjectorThis atomizes the liquid fuel and sprays the required amount of fuel into the

combustion chamber of the engine.

(4) Voltage RegulatorAs the name implies, this component regulates the output voltage of the generator. The

mechanism is described below against each component that plays a part in the cyclical process of

voltage regulation.

(1) Voltage Regulator: Conversion of AC Voltage to DC Current The voltage regulator takes

up a small portion of the generators output of AC voltage and converts it into DC current. Thevoltage regulator then feeds this DC current to a set of secondary windings in the stator, known

as exciter windings.

(2) Exciter Windings: Conversion of DC Current to AC CurrentThe exciterwindings now function similar to the primary stator windings and generate a

small AC current. The exciter windings are connected to units known as rotating

rectifiers.

(3) Rotating Rectifiers: Conversion of AC Current to DC CurrentThese

rectify the AC current generated by the exciter windings and convert it to DCcurrent. This DC current is fed to the rotor / armature to create an

electromagnetic field in addition to the rotating magnetic field of the rotor /

armature.

(4) Rotor / Armature: Conversion of DC Current to AC VoltageThe rotor / armature now

induces a larger AC voltage across the windings of the stator, which the generator now produces

as a larger output AC voltage.

This cycle continues till the generator begins to produce output voltage equivalent to its full

operating capacity. As the output of the generator increases, the voltage regulator produces less

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DC current. Once the generator reaches full operating capacity, the voltage regulator attains a

state of equilibrium and produces just enough DC current to maintain the generators output at

full operating level.

When you add a load to a generator, its output voltage dips a little. This prompts the voltage

regulator into action and the above cycle begins. The cycle continues till the generator outputramps up to its original full operating capacity.

(5) Cooling & Exhaust Systems(a) Cooling System

Continuous usage of the generator causes its various components to get heated up. It is essential

to have a cooling and ventilation system to withdraw heat produced in the process.

Raw/fresh water is sometimes used as a coolant for generators, but these are mostly limited to

specific situations like small generators in city applications or very large units over 2250 kW andabove. Hydrogen is sometimes used as a coolant for the stator windings of large generator units

since it is more efficient at absorbing heat than other coolants. Hydrogen removes heat from thegenerator and transfers it through a heat exchanger into a secondary cooling circuit that contains

de-mineralized water as a coolant. This is why very large generators and small power plantsoften have large cooling towers next to them. For all other common applications, both

residential and industrial, a standard radiator and fan is mounted on the generator and works as

the primary cooling system.

It is essential to check the coolant levels of the generator on a daily basis. The cooling system

and raw water pump should be flushed after every 600 hours and the heat exchanger should becleaned after every 2,400 hours of generator operation. The generator should be placed in an

open and ventilated area that has adequate supply of fresh air. The National Electric Code (NEC)

mandates that a minimum space of 3 feet should be allowed on all sides of the generator toensure free flow of cooling air.

(b) Exhaust SystemExhaust fumes emitted by a generator are just like exhaust from any other diesel or gasonline

engine and contain highly toxic chemicals that need to be properly managed. Hence, it is

essential to install an adequate exhaust system to dispose of the exhaust gases. This point cannot be emphasized enough as carbon monoxide poisoning remains one of the most common

causes for death in post hurricane affected areas because people tend to not even think about it

until its too late.

Exhaust pipes are usually made of cast iron, wrought iron, or steel. These need to be freestanding

and should not be supported by the engine of the generator. Exhaust pipes are usually attached to

the engine using flexible connectors to minimize vibrations and prevent damage to thegenerators exhaust system. The exhaust pipe terminates outdoors and leads away from doors,

windows and other openings to the house or building. You must ensure that the exhaust system

of your generator is not connected to that of any other equipment. You should also consult thelocal city ordinances to determine whether your generator operation will need to obtain an

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approval from the local authorities to ensure you are conforming to local laws a protect against

fines and other penalties.

(6) Lubricating SystemSince the generator comprises moving parts in its engine, it requires lubrication to ensure

durability and smooth operations for a long period of time. The generators engine is lubricatedby oil stored in a pump. You should check the level of lubricating oil every 8 hours of generator

operation. You should also check for any leakages of lubricant and change the lubricating oil

every 500 hours of generator operation.

(7) Battery ChargerThe start function of a generator is battery-operated. The battery charger keeps the generator

battery charged by supplying it with a precise float voltage. If the float voltage is very low, thebattery will remain undercharged. If the float voltage is very high, it will shorten the life of the

battery. Battery chargers are usually made of stainless steel to prevent corrosion. They are alsofully automatic and do not require any adjustments to be made or any settings to be changed. The

DC output voltage of the battery charger is set at 2.33 Volts per cell, which is the precise float

voltage for lead acid batteries. The battery charger has an isolated DC voltage output that doesinterfere with the normal functioning of the generator.

(8) Control PanelThis is the user interface of the generator and contains provisions for

electrical outlets and controls. The following article provides furtherdetails regarding thegenerator control panel. Different manufacturershave varied features to offer in the control panels of their units. Some of

these are mentioned below.

(a) Electric start and shut-downAuto start control panels automatically start your generator

during a power outage, monitor the generator while in operation, and automatically shut down

the unit when no longer required.

(b) Engine gaugesDifferent gauges indicate important parameters such as oil pressure,

temperature of coolant, battery voltage, engine rotation speed, and duration of operation.

Constant measurement and monitoring of these parameters enables built-in shut down of thegenerator when any of these cross their respective threshold levels.

(c) Generator gaugesThe control panel also has meters for the measurement of output current

and voltage, and operating frequency.

(d) Other controlsPhase selector switch, frequency switch, and engine control switch (manual

mode, auto mode) among others.

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(9) Main Assembly / FrameAll generators, portable or stationary, have customized housings that provide a structural base

support. The frame also allows for the generated to be earthed for safety.

Electromagnetic Induction

Electromagnetic induction is the production of a potential difference (voltage) across a conductor

when it is exposed to a varying magnetic field.

Michael Faraday is generally credited with the discovery of induction in 1831 though it mayhave been anticipated by the work of Francesco Zantedeschi in 1829. Around 1830 to 1832,

Joseph Henry made a similar discovery, but did not publish his findings until later.

Faraday's law of induction is a basic law of electromagnetism that predicts how a magnetic field

will interact with an electric circuit to produce an electromotive force (EMF). It is the

fundamental operating principle of transformers, inductors, and many types of electrical motors,

generators and solenoids.[

Electromagnetic induction was discovered independently by Michael Faraday and Joseph Henry

in 1831; however, Faraday was the first to publish the results of his experiments. In Faraday's

first experimental demonstration of electromagnetic induction (August 29, 1831), he wrapped

two wires around opposite sides of an iron ring or "torus" (an arrangement similar to a modern

toroidal transformer). Based on his assessment of recently discovered properties of

electromagnets, he expected that when current started to flow in one wire, a sort of wavewould travel through the ring and cause some electrical effect on the opposite side. He plugged

one wire into a galvanometer, and watched it as he connected the other wire to a battery.

Indeed, he saw a transient current (which he called a "wave of electricity") when he connected

the wire to the battery, and another when he disconnected it.This induction was due to the

change in magnetic flux that occurred when the battery was connected and disconnected.[6]

Within two months, Faraday had found several other manifestations of electromagnetic

induction. For example, he saw transient currents when he quickly slid a bar magnet in and out

of a coil of wires, and he generated a steady (DC) current by rotating a copper disk near the bar

magnet with a sliding electrical lead ("Faraday's disk").

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ELECTRIC ENERGY GENERATION IN POWER PLANTS

Electric Power Plants:

Electric Power Plants have a number of components in common and a

interesting study in the various forms and changes of energy necessar

To produce electricity.

Boiler Unit: Almost all of power plants operate by heating water

In a boiler unit into super heated steam at very high pressures.

The source of heat from combustion reactions may vary in fossil fuel

Plants from the source of fuels such as coal, oil, or natural gas.

Biomass or waste plant parts may also be used as a source of fuel.In some areas solid waste incinerators are also used as a source of he

All of these sources of fuels result in varying amounts of air pollution,

As well as, the carbon dioxide ( a gas implicated in global warming pro

In a nuclear power plant, the fission chain reaction of splitting nuclei

Provides the source of heat.

Turbine-Generator: The super heated steam is used to spin the blades

a turbine, which in turn is used in the generator to turn a coil of wires

Within a circular arrangements of magnets. The rotating coil of wire

in the magnets results in the generation of electricity.

Cooling Water: After the steam travels through the turbine, it must be

Cooled and condensed back into liquid water to start the cycle over ag

Cooling water can be obtained from a nearby river or lake.

The water is returned to the body of water 10 -20 degrees higher in

Temperature than the intake water. Alternate method is to use a

very tall cooling tower, where the evaporation of water falling

Through the tower provides the cooling effect.

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Creating Electricity using a Generator:

If a magnetic field can create a current then we have a

Means of generating electricity. Experiments showed that amagnetic just sitting next to a wire produced no current flow

Through that wire. However, if the magnet is moving, a

Current is induced in the wire. The faster the magnet moves,

The greater the induced current.

This is the principal behind simple electric generators in which a

Wire loop is rotated between to stationary magnetic.

This produces a continuously varying voltage which in turn produces an

Alternating current.

Diagram of a simple electric generator is shown on the left.

To generate electricity then, some (mechanical) mechanism is used

To turn a crank that rotates a loop of wire between stationary magnets.The faster the crank turns the more current that is generated.

In hydroelectric, the falling water turns the turbine.

The wind can also turn the turbine. In fossil fuel plants and nuclear plants

Water is heated to steam which turns the turbine.

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Hydroelectric power plant

Hydroelectric power plants use thepotential energy of water stored in a

reservoir to operate turbines. The

turbines are connected to largegenerators, and can operate on varying

volumes of water to adapt to changingdemand for electricity. A hydroelectric

power plant capacity is related to theheight and capacity of a reservoir and

require certain conditions in local

geography in addition to a water source. Hydro is a renewable energy source and more cost-effective than many other renewable sources of energy such as photovoltaic. Hydropower

currently provides about 25% of the world's electricity and is very flexible in scale. Commercial

installations range from 1 MW up to the largest installation to date of 18,400 Megawatts

(China).

Mannvit Engineering is a leading engineering firm in hydroelectric energy and has designed and

built complete hydropower plants (impoundment type), ancillary systems and powertransmission systems in Iceland and abroad. With installed systems from 1MW to 690MW,

Mannvit has completed a number of large and small systems, including:

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Thermal power plant

A thermal power station is a power plant in which the prime mover is steam driven. Water isheated, turns into steam and spins a steam turbine which drives an electrical generator. After it

passes through the turbine, the steam is condensed in a condenser and recycled to where it was

heated; this is known as a Rankine cycle. The greatest variation in the design of thermal powerstations is due to the different fuel sources. Some prefer to use the term energy center because

such facilities convert forms of heat energy into electricity.[ Some thermal power plants also

deliver heat energy for industrial purposes, for district heating, or for desalination of water aswell as delivering electrical power. A large part of human CO2 emissions comes from fossil

fueled thermal power plants; efforts to reduce these outputs are various and widespread.

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