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Electrical Fundamentals

Electrical Fundamentals. Board of INSURV on USS Trenton “First Electrified Naval Ship”. 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

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Electrical Fundamentals

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  1. Electrical Fundamentals

  2. Board of INSURV on USS Trenton“First Electrified Naval Ship”

  3. 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

  4. TERMINAL OBJECTIVE DESCRIBE and EXPLAIN the function and theory of shipboard electricity and its role in the electrical distribution system.

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

  6. 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

  7. Starring The “ATOM”

  8. VOLTAGE – “Electrical Pressure” 3 Factors necessary to produce an AC Voltage • Conductor • Magnetic Field • Relative motion between the two

  9. 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

  10. “RESPECT…NOT FEAR” • .001 Amps = “Tingling Sensation” (Shock Felt) • .01 Amps = “Clutching Current” • .1 Amps = May be Fatal

  11. OHM’s LAW Voltage = Current * Resistance E=IR or I=E/R R=E/I

  12. In SERIES…the Law Is: • Current (I) is COMMON throughout • Resistance (R) is ADDITIVE • Voltage (E) is ADDITIVE

  13. The Basic SERIES Circuit

  14. 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!

  15. How much total Current?How much total Resistance?

  16. “Shorts & Opens” • Electrical “SHORT” = Minimal Resistance • Electrical “OPEN” = Infinite Resistance

  17. INDUCTANCE AND CAPACITANCE • INDUCTOR: Opposes CHANGE in CURRENT • (Measured in “Henry’s”) • CAPACITOR: Opposes CHANGE in VOLTAGE • (Measured in “Farads”) • The COMBINED Opposition is called “Reactance” and measured in OHMS

  18. INDUCTOR

  19. Current “Limiter” in circuit

  20. INDUCTOR: “Friend” or “Foe?”

  21. CAPACITOR

  22. Theory of Operation

  23. Nothin’ To Play With!

  24. Use a Shorting Probe…Not your Fingers, Stupid!

  25. So what are they good for?

  26. POWER • “RATE at which work is being done” • Power = Current x Voltage • (Measured in WATTS) • FYI: 1 Horse Power = 746 Watts

  27. POWER (Cont) True - Power that actually does work. (KW Meter) Reactive - Power used by reactive elements. (KVAR - not useful) Apparent = combination of Ptrue andPreactive Power.

  28. 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

  29. The World of Electromagnetic Induction: AC baby!

  30. Single Phase Alternating Voltage Frequency = Cycles/sec = Hertz (Hz) One Cycle Voltage Time

  31. Frequency Calculation • Dependant on number of “POLES”, and SPEED of the rotor (prime mover RPM) F = n x s • 120 • F= FrequencyN = Number of Poles • S= Speed (RPM) of Rotor • 120 = standard formula constant

  32. I need more Power Scotty!

  33. Armature Reaction: Can’t Stop It

  34. Number and location varies from ship to ship, usually two or more Placed as far apart as feasible Ship’s Service Switchboards

  35. Switchboard

  36. EPCP operation • Remote operations • Allows the operator: • Start and stop generators • Monitor electrical plant • Parallel generators

  37. 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

  38. “A” Phase Ground Indication

  39. Ground Detector Operation • Only works when the test button is pushed • Must see lights flicker when pressing test button • Grounds don’t go through transformers • Light must be “out”

  40. Without a Ground

  41. With a Ground

  42. Isolating a Ground WATCH STANDER’S 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

  43. TRANSFORMERS

  44. Transformer Theory • Transfers AC Power from one circuit to another by Electromagnetic Induction • FREQUENCY is not changed • No Moving Parts

  45. XFMR Construction • Consist of PRIMARY and SECONDARY Windings • May be “Step-Up” or “Step-Down” • Determined by “Turns ratio” of Primary and Secondary Windings

  46. GROUNDS ON 115V SYSTEM

  47. 4000A 750A 100A 15A Fault Ld Ctr SWBD Distr Pnl Source Trips 4th 3rd 2nd 1st Selective Tripping Designed into the system Protective device closest to a fault trips Protects the rest of the system

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