Electrical Supply lect 5.ppt

8/18/2019 Electrical Supply lect 5.ppt

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Unit - 3

BUILDING SERVICES – I

Lecture - 5


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Electricity:Basic Concepts and Terminology

Source of electricity, generation to end user

connection, service connections


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•Electricity by defnition is electric current that

is used as a power source

What Is Electricity ?

• This electric current is generated in a power

plant, and then sent out over a power grid toyour homes, and ultimately to your power

outlets.• The movement of

charges such aselectrons is called

current, and this

electrical current is

Electric Current =

Charge Passing

Through A Given Area

-------------------------------

Time


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Electricity Generation: electrical energy has to

be made by conversion from some other form ofenergy

Generating Electricity


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e.g. hydroelectric generation

ur!ine: a fan-like device

which turns in response

to the pressure of falling

water


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Generator: a coil of wire

turned inside a magnet

generates electricity


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"o#er line$: electricity

generated is carried in

wires over long distancesto our homes


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e.g. tidal generation

-high & low tides occur twice daily

-tidal water movement can be used to turn a

turbine


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e.g. ther%al generation

-water is heated to make steam

-pressure builds & the steam can only

escape by passing through a turbine

-this turns the turbine


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&o$$il &uel: burning coal, oil, or natural gas

can be used to heat the water


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&o$$il &uel: burning coal, oil, or natural gas

can be used to heat the water

Radioacti'e (aterial: when the nuclei of

uranium atoms break apart huge amounts of

energy is released, which can be used to heatthe water

Bio%a$$: biodegradable wastes can be burned

to heat the water


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e.g. )ind

-the blades themselves act as a turbine to turn

the middle of the generator to produce

electricity

called #ind tur!ine$, not wind mills


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e.g. Light

*hoto'oltaic cell$: converts light directly into

electrical energy


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orld !lectricity "eneration


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• Electricity is supplied through “hot wires”,

comparable to pressured water supply pipes.

• At points along the wires are lighting outlets,switches, and receptacles. Turning on a light switchor plugging equipment into a receptacle is

comparable to opening a aucetvalve.

Electrical Supply

Electrical supply

Can be

compared to

Water supply


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Voltage

Equivalent to water pressure; pump controls waterpressure; generator or battery controls voltage;standard voltage is 12!2"; most common low voltageis 12V

voltage

water pressure

Can be

compared to


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#mperage

Electrical current; equivalent to $low o$ water %gal!sec&


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Conductors

)ire over w*ic* electrons are transmitted

Increase in wire number = decrease in size


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Copper )ire:'elation between +iameters and

#mperage and 'esistance


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,nsulators

-olds electrical current in proper pat*.similar to a *ose


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)attage

/nit o$ power; rate at w*ic* a deviceconverts current to anot*er $orm %*eator motor&

%Voltage 0 #mperage&


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)att*our: /nit o$ energy; measures amount o$energy!electricity used in one *our

Watts x hours of use=watthours orKWHR, eg,

!"" w x #$hrs = #$"" whrs%day

= #$ KWHRs

#$ KWHR%day x &" days%mo

= '#$ KWHR%mo


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+irect Current

+irect current: Current $lows in onedirection


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#lternating Current

#lternating current: Current $lows insingle direction but reverses direction atregular intervals


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(t*er terms

Series circuit: ,$ one lamp $ails. remaining lampsgo out

Parallel circuit: ,$ one lamp $ails. ot*ers remainlig*ted

Open circuit: Circuit is broen

Closed circuit: Circuit is complete

Short circuit: ,$ t*ere is a $ault. electricity willtae pat* o$ least resistance to reac* ground


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S*ort circuit

Electrical Supply lect 5.ppt

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