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Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
Halderman ch054 lecture
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Halderman ch054 lecture

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  • Figure 54-1 A typical alternator on a Chevrolet V-8 engine.
  • Figure 54-2 The end frame toward the drive belt is called the drive-end housing and the rear section is called the slip-ring-end housing.
  • Figure 54-3 An OAP on a Chevrolet Corvette alternator.
  • Figure 54-4 An exploded view of an overrunning alternator pulley showing all of the internal parts.
  • Figure 54-6 A cutaway of an alternator, showing the rotor and cooling fan that is used to force air through the unit to remove the heat created when it is charging the battery and supplying electrical power for the vehicle
  • Figure 54-7 Rotor assembly of a typical alternator. Current through the slip rings causes the “fingers” of the rotor to become alternating north and south magnetic poles. As the rotor revolves, these magnetic lines of force induce a current in the stator windings.
  • Figure 54-8 An exploded view of a typical alternator showing all of its internal parts including the stator windings.
  • Figure 54-9 A rectifier usually includes six diodes in one assembly and is used to rectify AC voltage from the stator windings into DC voltage suitable for use by the battery and electrical devices in the vehicle.
  • Figure 54-10 Magnetic lines of force cutting across a conductor induce a voltage and current in the conductor.
  • Figure 54-11 A sine wave (shaped like the letter S on its side) voltage curve is created by one revolution of a winding as it rotates in a magnetic field.
  • Figure 54-12 When three windings (A, B, and C) are present in a stator, the resulting current generation is represented by the three sine waves. The voltages are 120 degrees out of phase. The connection of the individual phases produces a three-phase alternating voltage.
  • Figure 54-13 Wye-connected stator winding.
  • Figure 54-14 As the magnetic field, created in the rotor, cuts across the windings of the stator, a current is induced. Notice that the current path includes passing through one positive (+) diode on the way to the battery and one negative (-) diode as a complete circuit is completed through the rectifier and stator.
  • Figure 54-15 Delta-connected stator winding.
  • Figure 54-16 A stator assembly with six, rather than the normal three, windings.
  • Figure 54-17 Typical voltage regulator range.
  • Figure 54-18 A typical electronic voltage regulator with the cover removed showing the circuits inside.
  • Figure 54-19 Typical General Motors SI-style alternator with an integral voltage regulator. Voltage present at terminal 2 is used to reverse bias the zener diode (D2) that controls TR2. The positive brush is fed by the ignition current (terminal I) plus current from the diode trio.
  • Figure 54-20 A coolant-cooled alternator showing the hose connections where coolant from the engine flows through the rear frame of the alternator.
  • Figure 54-21 A Hall-effect current sensor attached to the positive battery cable is used as part of the EPM system.
  • Figure 54-22 The amount of time current is flowing through the field (rotor) determines the alternator output.
  • Chart 54-1 The output voltage is controlled by varying the duty cycle as controlled by the PCM.
  • Transcript

    • 1. CHARGING SYSTEM 54
    • 2. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “D” (Charging System Diagnosis and Repair). </li></ul></ul><ul><ul><li>List the parts of a typical alternator. </li></ul></ul><ul><ul><li>Describe how an alternator works. </li></ul></ul><ul><ul><li>Explain how the powertrain control module (PCM) controls the charging circuit. </li></ul></ul>
    • 3. PRINCIPLES OF ALTERNATOR OPERATION
    • 4. Principles of Alternator Operation <ul><li>Terminology </li></ul><ul><ul><li>Purpose and function of charging system to keep battery fully charged. </li></ul></ul><ul><ul><li>Generator is SAE term for unit that generates electricity. </li></ul></ul><ul><ul><li>Alternator most commonly used term in the trade. </li></ul></ul>
    • 5. Principles of Alternator Operation <ul><li>Principles </li></ul><ul><ul><li>All electrical alternators use electromagnetic induction to generate electrical power from mechanical power. </li></ul></ul>
    • 6. Principles of Alternator Operation <ul><li>Principles </li></ul><ul><ul><li>Generation of current in conductor when conductor moved through magnetic field. </li></ul></ul>
    • 7. Principles of Alternator Operation <ul><li>Principles </li></ul><ul><ul><li>Amount of current generated can be increased by: </li></ul></ul><ul><ul><ul><li>Increasing speed of conductors through magnetic field. </li></ul></ul></ul><ul><ul><ul><li>Increasing number of conductors passing through magnetic field. </li></ul></ul></ul>
    • 8. Principles of Alternator Operation <ul><li>Principles </li></ul><ul><ul><li>Amount of current generated can be increased by: </li></ul></ul><ul><ul><ul><li>Increasing strength of magnetic field. </li></ul></ul></ul>
    • 9. Principles of Alternator Operation <ul><li>Changing AC to DC </li></ul><ul><ul><li>Alternator generates alternating current (AC). </li></ul></ul><ul><ul><li>Battery can only store direct current (DC). </li></ul></ul><ul><ul><li>AC changed to DC by diodes inside alternator. </li></ul></ul>
    • 10. ALTERNATOR CONSTRUCTION
    • 11. Alternator Construction <ul><li>Housing </li></ul><ul><ul><li>Two-piece cast aluminum housing. </li></ul></ul><ul><ul><ul><li>Drive-end (DE) housing. </li></ul></ul></ul><ul><ul><ul><li>Slip-ring-end (SRE) housing. </li></ul></ul></ul>
    • 12. Figure 54-1 A typical alternator on a Chevrolet V-8 engine.
    • 13. Figure 54-2 The end frame toward the drive belt is called the drive-end housing and the rear section is called the slip-ring-end housing.
    • 14. ALTERNATOR OVERRUNNING PULLEYS
    • 15. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>Many alternators equipped with overrunning alternator pulley (OAP). </li></ul></ul><ul><ul><li>Also called overrunning clutch pulley or alternator clutch pulley. </li></ul></ul>
    • 16. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>Helps eliminate noise and vibration in accessory drive belt system. </li></ul></ul><ul><ul><li>Inner race of clutch acts as nut as it screws on to alternator shaft. </li></ul></ul>
    • 17. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>Need special tools to remove and install. </li></ul></ul><ul><ul><li>Another type uses a dampener spring inside plus a one-way clutch. </li></ul></ul><ul><ul><ul><li>Isolating Decoupler Pulley (IDP) </li></ul></ul></ul>
    • 18. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>Another type uses a dampener spring inside plus a one-way clutch. </li></ul></ul><ul><ul><ul><li>Active Alternator Pulley (AAP) </li></ul></ul></ul><ul><ul><ul><li>Alternator Decoupler Pulley (ADP) </li></ul></ul></ul>
    • 19. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>Another type uses a dampener spring inside plus a one-way clutch. </li></ul></ul><ul><ul><ul><li>Alternator Overrunning Decoupler Pulley </li></ul></ul></ul><ul><ul><ul><li>Overrunning Alternator Dampener (OAD) </li></ul></ul></ul>
    • 20. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>OAP/OAD pulleys primarily used on diesel or luxury vehicles. </li></ul></ul><ul><ul><ul><li>Reduce accessory drive belt noise. </li></ul></ul></ul><ul><ul><ul><li>Improve life of accessory drive belt. </li></ul></ul></ul>
    • 21. Alternator Overrunning Pulleys <ul><li>Purpose and Function </li></ul><ul><ul><li>OAP/OAD pulleys primarily used on diesel or luxury vehicles. </li></ul></ul><ul><ul><ul><li>Improve fuel economy by allowing engine to operate at low idle speed. </li></ul></ul></ul>?
    • 22. (TECH TIP Page 579, column 2 top)
    • 23. (FREQUENTLY ASKED QUESTION Page 579, column 2)
    • 24. (TECH TIP Page 579, column 2 bottom)
    • 25. Figure 54-3 An OAP on a Chevrolet Corvette alternator.
    • 26. Figure 54-4 An exploded view of an overrunning alternator pulley showing all of the internal parts.
    • 27. ALTERNATOR COMPONENTS AND OPERATION
    • 28. Alternator Components and Operation <ul><li>Rotor Construction </li></ul><ul><ul><li>Rotating part of alternator. </li></ul></ul><ul><ul><li>Driven by accessory drive belt. </li></ul></ul>
    • 29. Alternator Components and Operation <ul><li>Rotor Construction </li></ul><ul><ul><li>Creates magnetic field of alternator and produces a current by electromagnetic induction. </li></ul></ul>
    • 30. Alternator Components and Operation <ul><li>Rotor Construction </li></ul><ul><ul><li>Constructed of many turns of copper wire wound over iron core attached to rotor shaft. </li></ul></ul><ul><ul><li>Claw poles bent over windings. </li></ul></ul>
    • 31. Figure 54-6 A cutaway of an alternator, showing the rotor and cooling fan that is used to force air through the unit to remove the heat created when it is charging the battery and supplying electrical power for the vehicle
    • 32. Alternator Components and Operation <ul><li>How Rotors Create Magnetic Fields </li></ul><ul><ul><li>When current flows through windings, metal pole pieces at each end become electromagnets. </li></ul></ul><ul><ul><li>Rotor fingers alternating north and south magnetic poles. </li></ul></ul>
    • 33. Alternator Components and Operation <ul><li>How Rotors Create Magnetic Fields </li></ul><ul><ul><li>Magnetic fields created between alternating pole piece fingers. </li></ul></ul><ul><ul><li>Individual magnetic fields produce current in stationary stator windings. </li></ul></ul>
    • 34. Figure 54-7 Rotor assembly of a typical alternator. Current through the slip rings causes the “fingers” of the rotor to become alternating north and south magnetic poles. As the rotor revolves, these magnetic lines of force induce a current in the stator windings.
    • 35. Alternator Components and Operation <ul><li>Rotor Current </li></ul><ul><ul><li>Current necessary for rotor windings conducted through slip rings with carbon brushes. </li></ul></ul>
    • 36. Alternator Components and Operation <ul><li>Rotor Current </li></ul><ul><ul><li>Maximum alternator output depends on number and gauge of rotor windings. </li></ul></ul><ul><ul><li>Current for field controlled by voltage regulator. </li></ul></ul>
    • 37. Alternator Components and Operation <ul><li>Stator Construction </li></ul><ul><ul><li>Stator consists of stationary coil windings inside alternator. </li></ul></ul><ul><ul><li>Stator supported between two halves of alternator housing. </li></ul></ul><ul><ul><li>As rotor revolves, moving magnetic field induces current in stator windings. </li></ul></ul>
    • 38. Figure 54-8 An exploded view of a typical alternator showing all of its internal parts including the stator windings.
    • 39. Alternator Components and Operation <ul><li>Diodes </li></ul><ul><ul><li>One-way electrical check valves. </li></ul></ul><ul><ul><li>Six diodes to convert AC to DC. </li></ul></ul><ul><ul><li>Rectifier. </li></ul></ul>
    • 40. Figure 54-9 A rectifier usually includes six diodes in one assembly and is used to rectify AC voltage from the stator windings into DC voltage suitable for use by the battery and electrical devices in the vehicle.
    • 41. Alternator Components and Operation <ul><li>Diode Trio </li></ul><ul><ul><li>Supplies current to brushes from stator windings. </li></ul></ul><ul><ul><li>One diode for each stator winding. </li></ul></ul>
    • 42. HOW AN ALTERNATOR WORKS
    • 43. How an Alternator Works <ul><li>Field Current is Produced </li></ul><ul><ul><li>Rotor inside alternator turned by belt and drive pulley. </li></ul></ul><ul><ul><ul><li>Belt and drive pulley turned by engine </li></ul></ul></ul>
    • 44. How an Alternator Works <ul><li>Field Current is Produced </li></ul><ul><ul><li>Magnetic field of rotor generates current in stator windings. </li></ul></ul><ul><ul><li>Field current creates alternating north and south pole on rotor. </li></ul></ul><ul><ul><li>Magnetic field between each finger of rotor. </li></ul></ul>
    • 45. Figure 54-10 Magnetic lines of force cutting across a conductor induce a voltage and current in the conductor.
    • 46. How an Alternator Works <ul><li>Current is Induced in the Stator </li></ul><ul><ul><li>Current increases as magnetic field induces current in each stator winding. </li></ul></ul><ul><ul><li>Peaks when magnetic field is strongest. </li></ul></ul>
    • 47. How an Alternator Works <ul><li>Current is Induced in the Stator </li></ul><ul><ul><li>Decreases as field moves away from stator winding. </li></ul></ul><ul><ul><li>Current generated described as sine wave or AC pattern. </li></ul></ul>
    • 48. How an Alternator Works <ul><li>Current is Induced in the Stator </li></ul><ul><ul><li>Each of three windings generates sine wave current. </li></ul></ul><ul><ul><li>Resulting currents combine into three-phase voltage output. </li></ul></ul><ul><ul><li>Current induced in stator windings connects to diodes. </li></ul></ul>
    • 49. Figure 54-11 A sine wave (shaped like the letter S on its side) voltage curve is created by one revolution of a winding as it rotates in a magnetic field.
    • 50. Figure 54-12 When three windings (A, B, and C) are present in a stator, the resulting current generation is represented by the three sine waves. The voltages are 120 degrees out of phase. The connection of the individual phases produces a three-phase alternating voltage.
    • 51. How an Alternator Works <ul><li>Wye-Connected Stators </li></ul><ul><ul><li>Star shape. </li></ul></ul><ul><ul><li>Most commonly used alternator stator winding connection. </li></ul></ul>
    • 52. How an Alternator Works <ul><li>Wye-Connected Stators </li></ul><ul><ul><li>Output current constant over broad alternator speed range. </li></ul></ul><ul><ul><li>Currents from stator must combine because two windings always connected in series. </li></ul></ul>
    • 53. Figure 54-13 Wye-connected stator winding.
    • 54. Figure 54-14 As the magnetic field, created in the rotor, cuts across the windings of the stator, a current is induced. Notice that the current path includes passing through one positive (+) diode on the way to the battery and one negative (−) diode as a complete circuit is completed through the rectifier and stator.
    • 55. How an Alternator Works <ul><li>Delta-Connected Stators </li></ul><ul><ul><li>Triangle shape. </li></ul></ul><ul><ul><li>Current induced in each winding flows to diodes in parallel circuit. </li></ul></ul>
    • 56. How an Alternator Works <ul><li>Delta-Connected Stators </li></ul><ul><ul><li>More current can flow than through series circuit (wye-type). </li></ul></ul><ul><ul><li>Used on alternators where high output at high-alternator RPM required. </li></ul></ul><ul><ul><li>Must be operated at high speed to produce maximum output. </li></ul></ul>
    • 57. Figure 54-15 Delta-connected stator winding.
    • 58. ALTERNATOR OUTPUT FACTORS
    • 59. Alternator Output Factors <ul><li>Voltage and current of an alternator depend on: </li></ul><ul><ul><li>Speed of rotation </li></ul></ul><ul><ul><li>Number of conductors </li></ul></ul><ul><ul><ul><li>High-output alternator: more turns of wire in stator windings </li></ul></ul></ul>
    • 60. Alternator Output Factors <ul><li>Voltage and current of an alternator depend on: </li></ul><ul><ul><li>Strength of magnetic field </li></ul></ul>
    • 61. Figure 54-16 A stator assembly with six, rather than the normal three, windings.
    • 62. ALTERNATOR VOLTAGE REGULATION
    • 63. Alternator Voltage Regulation <ul><li>Principles </li></ul><ul><ul><li>To charge battery, alternator must produce electrical pressure (voltage) higher than battery voltage. </li></ul></ul>
    • 64. Alternator Voltage Regulation <ul><li>Principles </li></ul><ul><ul><li>If zero amperes of current in field coil, alternator output is zero: no magnetic field, no output. </li></ul></ul><ul><ul><li>It is control of field current that controls output of alternator. </li></ul></ul>
    • 65. Alternator Voltage Regulation <ul><li>Principles </li></ul><ul><ul><li>Most voltage regulators control field current by controlling amount of field current through ground brush. </li></ul></ul><ul><ul><li>Voltage regulator opens and closes field circuit to maintain correct charging voltage. </li></ul></ul>
    • 66. Alternator Voltage Regulation <ul><li>Principles </li></ul><ul><ul><li>Electronic circuit of voltage regulator cycles between 10 and 7,000 times per second. </li></ul></ul>
    • 67. Figure 54-17 Typical voltage regulator range.
    • 68. Alternator Voltage Regulation <ul><li>Regulator Operation </li></ul><ul><ul><li>Field current controlled by opening and closing ground side of field circuit. </li></ul></ul><ul><ul><li>Zener diode makes voltage regulation possible. </li></ul></ul><ul><ul><ul><li>Blocks current flow until specific voltage reached, then permits flow. </li></ul></ul></ul>
    • 69. Alternator Voltage Regulation <ul><li>Regulator Operation </li></ul><ul><ul><li>Electronics usually housed in separate part inside alternator. </li></ul></ul>
    • 70. Figure 54-18 A typical electronic voltage regulator with the cover removed showing the circuits inside.
    • 71. Figure 54-19 Typical General Motors SI-style alternator with an integral voltage regulator. Voltage present at terminal 2 is used to reverse bias the zener diode (D2) that controls TR2. The positive brush is fed by the ignition current (terminal I) plus current from the diode trio.
    • 72. Alternator Voltage Regulation <ul><li>Battery Condition and Charging Voltage </li></ul><ul><ul><li>Condition and voltage of battery determine charging rate of alternator. </li></ul></ul><ul><ul><li>Charging system testing must be performed with reliable and known to be good battery. </li></ul></ul>
    • 73. Alternator Voltage Regulation <ul><li>Battery Condition and Charging Voltage </li></ul><ul><ul><li>Use of discharged battery during testing can mistakenly indicate defective alternator and/or voltage regulator. </li></ul></ul>
    • 74. Alternator Voltage Regulation <ul><li>Temperature Compensation </li></ul><ul><ul><li>Regulators provide way to increase charging voltage at low temperatures, lower charging voltage at high temperatures. </li></ul></ul><ul><ul><li>Compensates for temperature-controlled battery chemical changes. </li></ul></ul>
    • 75. Alternator Voltage Regulation <ul><li>Temperature Compensation </li></ul><ul><ul><li>Electronic voltage regulators use temperature-sensitive resistor (thermistor). </li></ul></ul><ul><ul><li>Provides lower resistance as temperature increases. </li></ul></ul>
    • 76. ALTERNATOR COOLING
    • 77. Alternator Cooling <ul><li>External fan. </li></ul><ul><li>Internal fan(s). </li></ul><ul><li>Both an external fan and an internal fan. </li></ul><ul><li>Coolant cooled. </li></ul>
    • 78. Figure 54-20 A coolant-cooled alternator showing the hose connections where coolant from the engine flows through the rear frame of the alternator.
    • 79. COMPUTER-CONTROLLED ALTERNATORS
    • 80. Computer-Controlled Alternators <ul><li>Types of Systems </li></ul><ul><ul><li>Computer can activate charging system by turning on and off field current to rotor. </li></ul></ul><ul><ul><li>Computer can monitor operation of alternator and increase engine speed if needed. </li></ul></ul>
    • 81. Computer-Controlled Alternators <ul><li>Types of Systems </li></ul><ul><ul><li>Computer can control alternator by controlling alternator output to match needs. </li></ul></ul>
    • 82. Computer-Controlled Alternators <ul><li>GM Electrical Power Management System </li></ul><ul><ul><li>Uses Hall-effect sensor attached to negative or positive battery cable. </li></ul></ul><ul><ul><li>Measures current leaving and entering battery. </li></ul></ul>
    • 83. Computer-Controlled Alternators <ul><li>GM Electrical Power Management System </li></ul><ul><ul><li>Engine control module (ECM) controls alternator by changing on-time of current through rotor. </li></ul></ul><ul><ul><li>On-time, called duty cycle, varies from 5% to 95%. </li></ul></ul>
    • 84. Computer-Controlled Alternators <ul><li>GM Electrical Power Management System </li></ul><ul><ul><li>Six modes of operation: </li></ul></ul><ul><ul><ul><li>Charge mode. </li></ul></ul></ul><ul><ul><ul><li>Fuel economy mode. </li></ul></ul></ul><ul><ul><ul><li>Voltage reduction mode. </li></ul></ul></ul>
    • 85. Computer-Controlled Alternators <ul><li>GM Electrical Power Management System </li></ul><ul><ul><li>Six modes of operation: </li></ul></ul><ul><ul><ul><li>Start-up mode. </li></ul></ul></ul><ul><ul><ul><li>Battery sulfation mode. </li></ul></ul></ul><ul><ul><ul><li>Headlight mode. </li></ul></ul></ul>
    • 86. Figure 54-21 A Hall-effect current sensor attached to the positive battery cable is used as part of the EPM system.
    • 87. Figure 54-22 The amount of time current is flowing through the field (rotor) determines the alternator output.
    • 88. Chart 54-1 The output voltage is controlled by varying the duty cycle as controlled by the PCM.
    • 89. Computer-Controlled Alternators <ul><li>Computer-Controlled Charging Systems </li></ul><ul><ul><li>Can pulse on or off as needed for maximum efficiency. </li></ul></ul><ul><ul><li>Engine idle improved by turning on alternator slowly. </li></ul></ul>
    • 90. Computer-Controlled Alternators <ul><li>Computer-Controlled Charging Systems </li></ul><ul><ul><li>Make adjustments to reduce load on electrical system if demand exceeds charging capacity. </li></ul></ul>
    • 91. Computer-Controlled Alternators <ul><li>Computer-Controlled Charging Systems </li></ul><ul><ul><li>Monitors charging system and set diagnostic trouble codes. </li></ul></ul><ul><ul><li>Charging system can be checked using scan tool. </li></ul></ul>
    • 92. TECH TIP <ul><li>Alternator Horsepower and Engine Operation </li></ul><ul><ul><li>Many technicians are asked how much power certain accessories require. A 100 ampere alternator requires about 2 horsepower from the engine. One horsepower is equal to 746 watts. Watts are calculated by multiplying amperes times volts. </li></ul></ul>BACK TO PRESENTATION <ul><ul><li>Power in watts = 100 A x 14.5 V = 1,450 W </li></ul></ul><ul><ul><li>1 hp = 746 W </li></ul></ul><ul><li>Therefore, 1,450 watts is about 2 horsepower. </li></ul><ul><li>Allowing about 20% for mechanical and electrical losses adds another 0.4 horsepower. Therefore, when someone asks how much power it takes to produce 100 amperes from an alternator, the answer is 2.4 horsepower. </li></ul><ul><li>Many alternators delay the electrical load to prevent the engine from stumbling when a heavy electrical load is applied. The voltage regulator or vehicle computer is capable of gradually increasing the output of the alternator over a period of several minutes. </li></ul><ul><li>Even though 2 horsepower does not sound like much, a sudden demand for 2 horsepower from an idling engine can cause the engine to run rough or stall. The difference in part numbers of various alternators is often an indication of the time interval over which the load is applied. Therefore, using the wrong replacement alternator could cause the engine to stall! </li></ul>
    • 93. FREQUENTLY ASKED QUESTION <ul><li>Can I Install an OAP or an OAD to My Alternator? </li></ul><ul><ul><li>Usually, no. An alternator needs to be equipped with the proper shaft to allow the installation of an OAP or OAD. This also means that a conventional pulley often cannot be used to replace a defective overrunning alternator pulley or dampener with a conventional pulley. </li></ul></ul>? <ul><li>Check service information for the exact procedure to follow. </li></ul>BACK TO PRESENTATION
    • 94. TECH TIP <ul><li>Always Check the OAP or OAD First </li></ul><ul><ul><li>Overrunning alternator pulleys and overrunning alternator dampeners can fail. The most common factor is the one-way clutch. If it fails, it can freewheel and not power the alternator or it can lock up and not provide the dampening as designed. </li></ul></ul><ul><li>If the charging system is not working, the OAP or OAD could be the cause, rather than a fault in the alternator itself. </li></ul><ul><li>In most cases, the entire alternator assembly will be replaced because each OAP or OAD is unique for each application and both require special tools to remove and replace. </li></ul>BACK TO PRESENTATION <ul><ul><li>Figure 54-5 A special tool is needed to remove and install overrunning alternator pulleys or dampeners. </li></ul></ul>
    • 95. TECH TIP <ul><li>The Voltage Display Can Be a Customer Concern </li></ul><ul><ul><li>A customer may complain that the voltmeter reading on the dash fluctuates up and down. This may be normal as the computer-controlled charging system commands various modes of operation based on the operating conditions. </li></ul></ul>BACK TO PRESENTATION <ul><li>Follow the vehicle manufacturer ’s recommended procedures to verify proper operation. </li></ul>

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