Chapter 21 LectureNotes

CHAPTER 21Charging System

Automotive Electricity and Electronics, 3/eBy James D. HaldermanCopyright 2011, 2009, 2005 Pearson Education, Inc.,Upper Saddle River, NJ 07458 All rights reserved.*

OBJECTIVESAfter studying Chapter 21, the reader will be able to:Prepare for ASE Electrical/Electronic Systems (A6) certification test content area D (Charging System Diagnosis and Repair).List the parts of a typical alternator.Describe how an alternator works.Explain how the powertrain control module (PCM) controls the charging circuit.


KEY TERMSAlternator Claw polesDelta winding Diodes Drive-end (DE) housingDuty cycle EPM IDP OAD OAP Rectifier Rotor Slip-ring-end (SRE) housing Stator Thermistor


PRINCIPLES OF ALTERNATOR OPERATIONTERMINOLOGYIt is the purpose and function of the charging system to keep the battery fully charged.PRINCIPLESAll electrical alternators use the principle of electromagnetic induction to generate electrical power from mechanical power. Electromagnetic induction involves the generation of an electrical current in a conductor when the conductor is moved through a magnetic field.CHANGING AC TO DC


ALTERNATOR CONSTRUCTIONHOUSINGAn alternator is constructed using a two-piece cast aluminum housing. A front ball bearing is pressed into the front housing, called the drive-end (DE) housing , to provide the support and friction reduction necessary for the belt-driven rotor assembly. The rear housing, or the slip-ring-end (SRE) housing , usually contains either a roller bearing or ball bearing support for the rotor and mounting for the brushes, diodes, and internal voltage regulator (if so equipped).


ALTERNATOR CONSTRUCTIONHOUSING


ALTERNATOR CONSTRUCTIONHOUSING


ALTERNATOR OVERRUNNING PULLEYSPURPOSE AND FUNCTIONMany alternators are equipped with an overrunning alternator pulley (OAP) , also called an overrunning clutch pulley or an alternator clutch pulley . The purpose of this pulley is to help eliminate noise and vibration in the accessory drive belt system, especially when the engine is at idle speed.


ALTERNATOR OVERRUNNING PULLEYSPURPOSE AND FUNCTION


ALTERNATOR OVERRUNNING PULLEYSPURPOSE AND FUNCTION


Alternator Horsepower and Engine OperationMany 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.Power in watts = 100 A x 14.5 V = 1,450 W1 hp = 746 WTherefore, 1,450 watts is about 2 horsepower.


Can I Install an OAP or an OAD to My Alternator?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. Check service information for the exact procedure to follow.


Always Check the OAP or OAD FirstOverrunning 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. If the charging system is not working, the OAP or OAD could be the cause, rather than a fault in the alternator itself.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.


Always Check the OAP or OAD First


ALTERNATOR COMPONENTS AND OPERATIONROTOR CONSTRUCTIONHOW ROTORS CREATE MAGNETIC FIELDSROTOR CURRENTSTATOR CONSTRUCTIONDIODESDIODE TRIO


ALTERNATOR COMPONENTS AND OPERATION








HOW AN ALTERNATOR WORKSHOW AN ALTERNATOR WORKSCURRENT IS INDUCED IN THE STATORWYE-CONNECTED STATORSDELTA-CONNECTED STATORS


HOW AN ALTERNATOR WORKS










ALTERNATOR OUTPUT FACTORSThe output voltage and current of an alternator depend on the following factors.Speed of rotationNumber of conductorsStrength of the magnetic field


ALTERNATOR VOLTAGE REGULATIONPRINCIPLESREGULATOR OPERATIONBATTERY CONDITION AND CHARGING VOLTAGETEMPERATURE COMPENSATION


ALTERNATOR VOLTAGE REGULATION






ALTERNATOR COOLINGAlternators create heat during normal operation and this heat must be removed to protect the component inside, especially the diodes and voltage regulator. The types of cooling include:External fanInternal fan(s)Both an external fan and an internal fanCoolant cooled


ALTERNATOR COOLING


COMPUTER-CONTROLLED ALTERNATORSTYPES OF SYSTEMSGM ELECTRICAL POWER MANAGEMENT SYSTEMCOMPUTER-CONTROLLED CHARGING SYSTEMS


COMPUTER-CONTROLLED ALTERNATORS






The Voltage Display Can Be a Customer ConcernA 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. Follow the vehicle manufacturers recommended procedures to verify proper operation.


SUMMARYAlternator output is increased if the speed of the alternator is increased.The parts of a typical alternator include the drive-end (DE) housing, slip-ring-end (SRE) housing, rotor assembly, stator, rectifier bridge, brushes, and voltage regulator.The magnetic field is created in the rotor.The alternator output current is created in the stator windings.The voltage regulator controls the current flow through the rotor winding.


REVIEW QUESTIONSHow can a small electronic voltage regulator control the output of a typical 100 ampere alternator?What are the component parts of a typical alternator?How is the computer used to control an alternator?Why do voltage regulators include temperature compensation?How is AC voltage inside the alternator changed to DC voltage at the output terminal?What is the purpose of an OAP or OAD?


CHAPTER QUIZ1.Technician A says that the diodes regulate the alternator output voltage. Technician B says that the field current can be computer controlled. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ2.A magnetic field is created in the ________ in an alternator (AC alternator).StatorDiodes RotorDrive-end frame


CHAPTER QUIZ3.The voltage regulator controls current through the ________ .Alternator brushesRotor Alternator fieldAll of the above


CHAPTER QUIZ4.Technician A says that two diodes are required for each stator winding lead. Technician B says that diodes change alternating current into direct current. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ5.The alternator output current is produced in the ________ .StatorRotor BrushesDiodes (rectifier bridge)


CHAPTER QUIZ6.Alternator brushes are constructed from ________.CopperAluminum CarbonSilver-copper alloy


CHAPTER QUIZ7.How much current flows through the alternator brushes?All of the alternator output flows through the brushes25 to 35 A, depending on the vehicle10 to 15 A2 to 5 A


CHAPTER QUIZ8.Technician A says that an alternator overrunning pulley is used to reduce vibration and noise. Technician B says that an overrunning alternator pulley or dampener uses a one-way clutch. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ9.Operating an alternator in a vehicle with a defective battery can harm the ________.Diodes (rectifier bridge)StatorVoltage regulatorBrushes


CHAPTER QUIZ10.Technician A says that a wye-wound stator produces more maximum output than the same alternator equipped with a delta-wound stator. Technician B says that an alternator equipped with a delta-wound stator produces more maximum output than a wye-wound stator. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B

Chapter 21 LectureNotes

Documents

Transcript of Chapter 21 LectureNotes