Electrical Fundamentals

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Electrical Fundamentals
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Board of INSURV on USS TrentonFirst Electrified
Naval Ship
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REFERENCES

• NSTM 300 ELECTRIC PLANT GENERAL
• NAVEDTRA 14344 ELECTRICIANS MATE
• 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 shipboard electricity and its role in the
  electrical distribution system.

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ENABLING OBJECTIVES

• State the basic units of measure, symbols or
  abbreviations for various electrical terms.
• Define Ohms law
• State the three requirements for electromagnetic
  induction
• Define the types of AC power
• Describe the internal parts of a generator

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More Objectives

• State the functions of a governor and a voltage
  regulator
• Explain the theory of operation of transformer
  action
• Explain a real ungrounded electrical system
• Describe Selective and Selected Tripping

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Starring The ATOM
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VOLTAGE Electrical Pressure

• 3 Factors necessary to produce an AC Voltage
• 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 given point 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
EIR
or
IE/R RE/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 are Different

• VOLTAGE (E) is COMMON in every branch
• 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 Minimal Resistance
• Electrical OPEN Infinite Resistance

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INDUCTANCE AND CAPACITANCE

• INDUCTOR Opposes CHANGE in CURRENT
• (Measured in Henrys)
• CAPACITOR Opposes CHANGE in VOLTAGE
• (Measured in Farads)
• The COMBINED Opposition is called Reactance
  and measured in OHMS

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INDUCTOR
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Current Limiter in circuit
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INDUCTOR Friend or Foe?
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CAPACITOR
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Theory of Operation
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Nothin To Play With!
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Use a Shorting ProbeNot your Fingers, Stupid!
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So what are they good for?
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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 reactive
elements. (KVAR - not useful) Apparent
combination of Ptrue and Preactive Power.
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Power Factor (PF)

• Ratio of TRUE Power (Wattmeter), to APPARENT
  Power (KVA Ammeter x Voltmeter).
• .8 PF is Standard on Naval Ships
• Identifies Power Lost due to Reactive Elements
• TP KW POWER FACTOR
• AP KVA

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Leading or Lagging?

• Current LAGS Voltage in predominantly
  Inductive Circuits
• Current LEADS Voltage in Capacitive Circuits
• Ships have more cabling (wires) than capacitors
  and therefore have a LAGGING Power factor.

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ELI the ICE Man
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The World of Electromagnetic Induction AC baby!
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Single Phase Alternating Voltage
Frequency Cycles/sec Hertz (Hz)
One Cycle
Voltage
Time
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Frequency Calculation

• Dependant on number of POLES, and SPEED 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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I need more Power Scotty!
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Armature Reaction Cant Stop It
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Ships Service Switchboards

• Number and location varies from ship to ship,
  usually two or more
• Placed as far apart as feasible

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Switchboard
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EPCP operation

• Remote operations
• Allows the operator
• Start and stop generators
• Monitor electrical plant
• Parallel generators

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Ground Detector Lights

• Indicates presence of a low insulation resistance
• Three lamps and test switch
• Normally illuminated
• Faulty phase will be indicated by a dark lamp
  when in test position

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A Phase Ground Indication
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Ground Detector Operation

• Only works when the test button is pushed
• Must see lights flicker when pressing test button
• Grounds dont go through transformers
• Light must be out

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Without a Ground
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With a Ground
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Isolating a Ground

• WATCH STANDERS ACTIONS
• OBTAIN PERMISSION FROM EOOW (via CHENG, via CO)
• SPLIT ELECTRICAL BUS TO ISOLATE SWITCHBOARD TO
  LOCALIZE GROUND
• RE-PARALLEL ELECTRICAL BUS
• SECURE BREAKERS ON AFFECTED SWITCHBOARD ONE AT A
  TIME UNTIL GROUND GOES AWAY
• 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 to another by
  Electromagnetic Induction
• FREQUENCY is not changed
• No Moving Parts

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XFMR Construction

• Consist of PRIMARY and SECONDARY Windings
• May be Step-Up or Step-Down
• Determined by Turns ratio of Primary and
  Secondary Windings

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GROUNDS ON 115V SYSTEM
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Selective Tripping
Designed into the system
Protective device closest to a fault trips
Protects the rest of the system
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Selective Tripping
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SELECTED TRIPPING
Is manually controlled by the operator. This form
of isolation is usually reserved for ground
isolation or equipment trouble- shooting.
Normally supervised by the EOOW.
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What IS a Real Ungrounded System?

• No Ground Conductors
• No Neutrals
• All Hots
• In THEORY, one could touch a live conductor and
  not get shocked, since there is no return path
  for current.but JUST in THEORY!

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ANY QUESTIONS?
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??????????

• What are the 3 requirements for Electro-Magnetic
  Induction?
• What is OHMS Law? What is the Power Formula?
• What is Power Factor?

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More of the Same.

• What is Inductance and Capacitance?
• What tool do we use to discharge a Capacitor?
• What is the frequency formula?

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And Lastly

• What is selective tripping?
• What is armature reaction and how does our
  generation system compensate for it?
• What is effective capacitance?

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Electrical Fundamentals Review