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Power (Electrical and Ignition Systems)

Terms in this set (51)

ENGINE ELECTRICAL SYSTEM
Governs the functions of all electrical
components of the engine (ignition,
starting, accessories, etc.
Electromagnetic Induction
Chemical Reaction (Battery)
Electricity generation through:
1. To supply current to start the engine
2. To supplement the vehicle electrical load
requirement whenever it exceeds the
maximum output of the charging system (during idle speed)
3. To act as a voltage stabilizer in charging system
STORAGE BATTERIES (FUNCTIONS)
1. positive material
2. negative material
3. electrolyte
4. container
STORAGE BATTERIES (MAIN COMPONENTS)
• Each cell in a lead acid battery has a potential of approximately 2 V.
• Cells in lead-acid batteries are connected in series
• A 6-V battery has 3 cells; a 12-V battery will have six cells
Construction of Lead-Acid Batteries (BATTERY VOLTAGES)
• Can be measured using a hydrometer
• Readings must be corrected to account for the electrolyte expansion at higher temperatures and contraction at lower temperatures
Lead-Acid Batteries (STATE OF CHARGE)
Maintenance-Free Batteries
Conventional Batteries
and
Maintenance-Free Batteries
Conventional Batteries:
• Include a small amount of antimony in the plates for
strengthening
• Antimony promotes the formation oh H2 and O2
during charging and the escape of these gases causes
gradual loss of H2O from the electrolyte
• Antimony is replaced by calcium which greatly
reduces gas formation
• Do not have removable cell cap for water
replenishment
Maintenance-Free Batteries:
Ampere-Hour Rating
Cold Cranking Rating
Reserve Capacity Rating
Battery Ratings
Ampere-Hour Rating
• Example: 120 AH battery can deliver 15 A for 8 hours for a stationary type engine
• Becoming an obsolete rating system for engine batteries
Cold Cranking Rating
Number of amperes a battery can deliver continuously for 30 s while maintaining a cell voltage of at least 1.2 V per cell (gasoline engines)
Reserve Capacity Rating
Measure of the ability of the battery to supply
current for ignition, lights, & accessories
without recharging
Cold Cranking Rating
90 s while maintaining a cell voltage of at least 1 V per cell (diesel engines)
Reserve Capacity Rating and Cold Cranking Rating
Developed by SAE and Battery Council International (BCI)
Reserve Capacity Rating
Number of minutes the battery can deliver 25
A continuously before the cell voltage falls
below 1.75 V
Battery Handling and Maintenance
Sulfation and Storage
Sulfation
Lead sulfate in the plates can crystallize into hard
deposits if a partially discharged battery is stored for
a month or more
Sulfation
Reduces the ability of the plates to transfer current
Storage
Batteries will gradually discharge during high-
temperature storage (completely discharged within 3
months at 40 °C)
Storage
Should be stored at temperatures 0 °C to 16 °C
Battery Safety
Explosion and Electrolyte Burn
Explosion
Hydrogen gas (highly flammable) is produced when a
battery is charged (lighters should not be used to check
electrolyte levels)
Explosion
Proper connections should be observed (to avoid
electrical spark) - grounded terminal should be
connected last or disconnected first
Electrolyte Burn
Electrolyte can create holes in clothing, burn the skin
and can cause blindness
Electrolyte Burn
Rubber gloves and eye protection should be worn and
the work should be done in well ventilated area
CHARGING CIRCUITS
A battery can only supply the electrical needs of a
tractor/vehicle for one to two hours before
discharging
CHARGING CIRCUITS
Charging can be accomplished using generators or
alternators
CHARGING CIRCUITS
Generators/alternators help the battery supply
current during periods of high demands
CHARGING CIRCUITS
During periods of low demand, generators/
alternators supply the entire demand and recharges
the battery
ALTERNATORS
Replaced generators in recent years since generators cannot meet the electrical demand of large vehicles
ALTERNATORS
More compact than generators
ALTERNATORS
Can supply more current at low speeds
STARTER MOTOR
Cranks the engine by converting electrical energy into rotational mechanical energy
STARTER MOTOR
Delivers the required large amounts of energy in short bursts
STARTER MOTOR
Extended cranking must be avoided to prevent overheating
IGNITION SYSTEMS
Developed for firing spark plugs in spark ignition systems
IGNITION SYSTEMS
Must generate 15 kV - 30 kV potential across the spark plug gap to initiate burning of air-fuel mixture
IGNITION SYSTEMS Most common designs
Battery ignition system
Magneto ignition system
MUTUAL INDUCTION
Creation of a voltage in the secondary winding by a
changing voltage in the primary winding
BATTERY IGNITION SYSTEM
Commonly used in multi-cylinder engines
MAGNETO IGNITION SYSTEM
Commonly used in single cylinder engines
SPARK PLUG
converts the secondary voltage from an ignition system into an arc across the electrode gap
SPARK PLUG
Center electrode is made of a nickel, chromium or tungsten alloy
SPARK PLUG
Reach varies from 10 to 20 mm (plugs w/ excessive reach may be hit by the piston)
SPARK PLUG
Diameter of the threaded end determines the size (10, 12, 14, 16, 18 mm)
SPARK PLUG
Electrode gap ranges from 0.5 to 1.0 mm
SPARK PLUG HEAT RANGE
determined by the distance heat must travel before
escaping the spark plug shell
SPARK PLUG HEAT RANGE
Use of excessively cold plugs promotes sluggish combustion
SPARK PLUG HEAT RANGE
Use of excessively hot plugs promotes preignition
SPARK PLUG HEAT RANGE
Long-reach spark ,plugs run hotter and short-reach plugs run colder
Sets found in the same folder