ABYC Marine Electrical flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Ohm's law formula
- Ohm's law states that voltage equals current multiplied by resistance (E = I × R); it also rearranges to I = E/R and R = E/I for DC circuit calculations.
- DC power formula
- Electrical power in a DC circuit equals voltage times current (P = E × I); it can also be calculated as P = I²R or P = E²/R when current or voltage is unknown.
- Parallel circuit rule
- In a parallel circuit the voltage across each branch is the same, branch currents add to total current, and total resistance is found from 1/R_total = 1/R1 + 1/R2 + ... .
- Voltage drop limit
- ABYC E-11 recommends total DC voltage drop no greater than 10 percent of nominal system voltage, and no more than 3 percent for navigation lights, electronics, and other critical loads.
- Series circuit rule
- In a series circuit the same current flows through every component, voltages across components add to source voltage, and total resistance equals the sum of individual resistances.
- Flooded battery 50 percent
- A rested 12-volt flooded lead-acid battery at 50 percent state of charge typically reads about 12.24 volts at 77°F (25°C); specific gravity is roughly 1.190.
- Three-stage charging
- Lead-acid three-stage charging uses bulk constant-current, absorption constant-voltage, and float constant-voltage stages; absorption voltage is about 14.4 volts for flooded batteries at 77°F.
- Battery capacity rating
- Amp-hour capacity is measured at the 20-hour discharge rate; reserve capacity is minutes at 25 amps, and cold cranking amps is the current a battery delivers at 0°F for 30 seconds.
- Battery switch BOTH
- The BOTH position parallels two battery banks for combined loads or charging; it can drain both banks and should not be used to combine a deeply discharged bank with a charged one.
- LiFePO4 charging limit
- Lithium iron phosphate batteries must not be charged below 0°C (32°F); charging at freezing can cause lithium plating and permanent damage, so a battery management system blocks charge current.
- Battery installation rules
- ABYC E-10 requires batteries to be secured against movement, terminals protected from short circuits, ignition sources excluded, and flooded batteries ventilated to remove hydrogen gas.
- Overcurrent protection distance
- ABYC E-11 requires overcurrent protection within 7 inches (178 mm) of the power source; 40 inches (1.0 m) is allowed when the conductor is enclosed in a sheath or raceway.
- DC negative color code
- ABYC E-11 recommends yellow insulation for the DC negative conductor and red for the DC positive, avoiding black because black identifies the AC ungrounded hot conductor.
- Breaker rating rule
- A fuse or circuit breaker must be rated to protect the conductor's ampacity after temperature and bundling derating; its rating must not exceed the conductor ampacity, regardless of load current.
- Marine conductor type
- Marine DC wiring uses stranded tinned-copper conductors with 105°C insulation, crimped solderless terminals, and adhesive heat-shrink; solid wire and wire nuts are not acceptable.
- Conductor support interval
- ABYC E-11 requires conductors to be supported at intervals not exceeding 18 inches (450 mm) and protected from chafe, sharp edges, and heat sources.
- DC grounding connection
- The DC negative system is bonded to the engine block or a common grounding bus, and that point is connected to the AC safety ground so the system has one common ground reference.
- Shore power neutral bond
- On shore power the neutral is bonded to ground at the shore source, not on board; bonding neutral and ground on board creates a parallel ground path and defeats ground fault protection.
- ELCI trip threshold
- An equipment leakage circuit interrupter protects the whole shore power circuit and trips at about 30 milliamps of leakage; ABYC requires it at or near the shore power inlet.
- GFCI trip threshold
- A ground fault circuit interrupter trips at about 5 milliamps and is required for receptacles in galley, head, weather deck, and other wet or damp locations on boats.
- Galvanic isolator function
- A galvanic isolator is installed in series with the shore power safety ground; it blocks low-voltage galvanic DC current while passing AC fault current to protect underwater metals.
- Generator neutral bonding
- A generator or inverter operating as a separately derived AC source must have its neutral bonded to its safety ground at the source, and the transfer switch must switch the neutral.
- Sacrificial anode selection
- Zinc or aluminum anodes are used in salt water and magnesium anodes in fresh water; the anode must be electrically connected to the protected metal and replaced when about half consumed.
- Bonding system purpose
- The bonding system connects underwater metal fittings to a common bus and to anodes so they remain at the same potential, reducing galvanic corrosion and electric shock hazards.
- Lightning down conductor
- A lightning protection system uses an air terminal at the highest point, a down conductor of at least 8 AWG copper, and a ground plate bonded to major metal fittings.
- Stray current corrosion
- Stray current corrosion occurs when external DC current leaves a submerged metal fitting into the water; it is detected with a clamp meter and often traced to faulty wiring or shore power.
- AC ground connection point
- The AC safety ground connects to the DC grounding system and bonding system at one point, usually the engine block or a dedicated grounding bus, to avoid ground loops.
- Inverter output waveform
- Pure sine wave inverters produce smooth AC similar to utility power and run sensitive electronics; modified sine wave inverters are cheaper but can cause overheating and interference.
- Motor overload protection
- Motor branch circuits require short-circuit protection sized to the conductor and separate overload protection sized to the motor nameplate current; overload devices protect the motor from sustained overcurrent.
- Voltage drop testing
- A voltage drop test measures potential difference across a connection or conductor while current flows; excessive drop indicates high resistance from corrosion, loose terminals, or undersized wire.
- Insulation resistance test
- A megohmmeter applies a high DC voltage to an isolated conductor and measures leakage to ground; low insulation resistance indicates moisture, damage, or breakdown in the wiring.
- Generator continuous rating
- A marine generator's continuous rating is the power it can supply indefinitely; standby or intermittent ratings apply only for short periods and should not be used for continuous loads.