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Electrical Fundamentals

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Trenton

First Electrified Naval Ship

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REFERENCES

NSTM 300 ELECTRIC PLANTGENERAL

NAVEDTRA 14344 ELECTRICIANSMATE

NSTM 310 GENERATORS/CONVERSION EQUIP

NSTM 320 DISTRIBUTION SYSTEMS NEETS MOD 14173 INTRO TO DIRECT

CURRENT NEETS MOD 14174 INTRO TO AC

CIRCUITS

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TERMINAL OBJECTIVE

DESCRIBE and EXPLAIN the

function and theory of shipboardelectricity and its role in theelectrical distribution system.

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ENABLING OBJECTIVES

State the basic units of measure,symbols or abbreviations for variouselectrical terms.

Define Ohms law State the three requirements for

electromagnetic induction

Define the types of AC power Describe the internal parts of agenerator

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More Objectives

State the functions of a governor and avoltage regulator

Explain the theory of operation of

transformer action Explain a real ungrounded electrical

system

Describe Selective and SelectedTripping

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Starring The ATOM

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VOLTAGE ElectricalPressure

3 Factors necessary to produce an ACVoltage

Conductor Magnetic Field Relative motion between the two

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Current -What is it?

Voltage and Complete Path Needed Movement of Electrons Past a Given

Point (Measured in AMPS)

1 Coulomb in 1 sec. past a givenpoint = 1 AMP

Coulomb= 6.28 x 1018

electrons

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RESPECTNOT FEAR

.001 Amps = Tingling Sensation(Shock Felt)

.01 Amps = Clutching Current

.1 Amps = May be Fatal

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OHMs LAW

Voltage = Current *

Resistance E=IR

or

I=E/R R=E/I

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In SERIESthe Law Is:

Current (I) is COMMON throughout

Resistance (R) is ADDITIVE

Voltage (E) is ADDITIVE

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The Basic SERIES Circuit

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In PARALLEL, the Laws areDifferent:

VOLTAGE (E) is COMMON in everybranch

CURRENT (I) is Additive

The TOTAL circuit RESISTANCE (R) is

LESS than any one Branch!

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How much total Current?How much total Resistance?

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Shorts & Opens

Electrical SHORT = MinimalResistance

Electrical OPEN = Infinite Resistance

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INDUCTANCE ANDCAPACITANCE

INDUCTOR: Opposes CHANGE inCURRENT

(Measured in Henrys)

CAPACITOR: Opposes CHANGE inVOLTAGE

(Measured in Farads)

The COMBINED Opposition is calledReactance and measured in OHMS

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INDUCTOR

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Current Limiter in circuit

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INDUCTOR: FriendorFoe?

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CAPACITOR

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TheoryofOperation

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Nothin To Play With!

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Use a Shorting ProbeNotyour Fingers, Stupid!

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So what are they goodfor?

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POWER

RATE at which work is being done

Power = Current x Voltage (Measured in WATTS)

FYI: 1 Horse Power = 746 Watts

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POWER

(Cont)True - Power that actually does work.(KW Meter)

Reactive - Power used by reactiveelements.(KVAR - not useful)

Apparent = combination ofPtrue andPreactivePower.

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Power Factor (PF)

Ratio of TRUE Power (Wattmeter), toAPPARENT Power (KVA: Ammeter xVoltmeter).

.8 PF is Standard on Naval Ships

Identifies Power Lost due to Reactive

Elements TP = KW = POWER FACTOR AP KVA

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Leadingor Lagging?

Current LAGS Voltage in predominantlyInductive Circuits

Current LEADS Voltage in Capacitive

Circuits

Ships have more cabling (wires) than

capacitors and therefore: have aLAGGING Power factor.

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ELI the ICE Man

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Electromagnetic Induction:

AC baby!

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Frequency = Cycles/sec = Hertz(Hz) One

Cycle

Voltage

Time

Single Phase AlternatingVoltage

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Frequency Calculation

Dependant on number of POLES, andSPEED of the rotor (prime mover RPM)

F = n x s

120 F= Frequency N = Number of Poles

S= Speed (RPM) of Rotor

120 = standard formula constant

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A R i C

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Armature Reaction: CantStop It

p s er ce

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p s erv ceSwitchboards

Number and location varies from ship toship, usually two or more

Placed as far apart as feasible

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Switchboard

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EPCPoperation

Remote operations Allows the operator:o

Start and stop generatorsoMonitor electrical plantoParallel generators

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GroundDetectorLights

Indicates presence of a lowinsulation resistance

Three lamps and test switchoNormally illuminatedoFaulty phase will be indicated by a

dark lamp when in test position

ase roun

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ase roun Indication

roun e ec or

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roun e ec orOperation

Only works when thetest button is pushed

Must see lights

flicker whenpressing test button Grounds dont go

throughtransformers

Light must be out

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WithoutaGround

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WithaGround

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IsolatingaGround

WATCH STANDERS ACTIONS:1.OBTAIN PERMISSION FROM EOOW (via

CHENG, via CO)2.SPLIT ELECTRICAL BUS TO ISOLATE

SWITCHBOARD TO LOCALIZE GROUND3.RE-PARALLEL ELECTRICAL BUS4.SECURE BREAKERS ON AFFECTED

SWITCHBOARD ONE AT A TIME UNTILGROUND GOES AWAY

5.NON-VITALS FIRST LIKELY DEVICES - GALLEY EQUIPMENT,

EQUIPMENT THAT WAS RECENTLY PLACED

ONLINE

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TRANSFORMERS

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Transformer Theory

Transfers AC Power from one circuit toanother by Electromagnetic Induction

FREQUENCY is not changed

No Moving Parts

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XFMR Construction

Consist of PRIMARY and SECONDARYWindings

May be Step-Up or Step-Down

Determined by Turns ratio of Primaryand Secondary Windings

GROUNDS ON 115V

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GROUNDS ON 115VSYSTEM

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Selective Tripping

Source Level

Switchboard Level

Load Center

Level

CustomerLevel

Fused Loads

100 A

250 A

1600 A

10 - 30 A

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What IS a Real Ungrounded

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What IS a Real UngroundedSystem?

No Ground Conductors No Neutrals All Hots

In THEORY, one could touch a liveconductor and not get shocked, sincethere is no return path for current.butJUST in THEORY!

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ANYQUESTIONS?

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??????????

What are the 3 requirements forElectro-Magnetic Induction?

What is OHMS Law? What is thePower Formula?

What is Power Factor?

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And Lastly

What is selective tripping?

What is armature reaction and how

does our generation systemcompensate for it?

What is effective capacitance?

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Electrical FundamentalsReview