AUT 242 – Automotive Electricity II

1. AUT 242 – Automotive Electricity II Chapter 21 – Charging System

2. After 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. OBJECTIVES

3. Alternator Claw poles Delta winding Diodes Drive-end (DE) housing Duty cycle EPM IDP OAD OAP Rectifier Rotor Slip-ring-end (SRE) housing Stator Thermistor KEY TERMS

4. TERMINOLOGY • It is the purpose and function of the charging system to keep the battery fully charged. • PRINCIPLES • All 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 PRINCIPLES OF ALTERNATOR OPERATION

5. An 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

6. The end frame toward the drive belt is called the drive-end housing and the rear section is called the slip-ring-end housing. ALTERNATOR CONSTRUCTIONHOUSING

7. Many 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

8. An exploded view of an overrunning alternator dampener showing all of the internal parts. ALTERNATOR OVERRUNNING PULLEYSPURPOSE AND FUNCTION

9. 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. • Power in watts =100 A x14.5 V =1,450 W • 1 hp =746 W • Therefore, 1,450 watts is about 2 horsepower. Tech Tip Alternator Horsepower and Engine Operation

10. 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. Tech Tip Can I Install an OAP or an OAD to My Alternator?

11. 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. • 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. Tech Tip Always Check the OAP or OAD First

12. A special tool is needed to remove and install overrunning alternator pulleys or dampeners. Always Check the OAP or OAD First

13. ROTOR CONSTRUCTION • HOW ROTORS CREATE MAGNETIC FIELDS • ROTOR CURRENT • STATOR CONSTRUCTION • DIODES • DIODE TRIO ALTERNATOR COMPONENTS AND OPERATION

14. Cutaway of an alternator, showing the rotor and cooling fan ALTERNATOR COMPONENTS AND OPERATION

15. 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. ALTERNATOR COMPONENTS AND OPERATION

16. STATORS • The stator is the stationary coil winding inside the alternator. • The stator is supported between the two halves of the generator housing and there are three copper wire windings wound on a laminated metal core.

17. An exploded view of a typical alternator showing all of its internal parts including the stator windings. ALTERNATOR COMPONENTS AND OPERATION

18. 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 the battery and electrical system. ALTERNATOR COMPONENTS AND OPERATION

19. HOW AN ALTERNATOR WORKS • HOW AN ALTERNATOR WORKS • CURRENT IS INDUCED IN THE STATOR • WYE-CONNECTED STATORS • DELTA-CONNECTED STATORS

20. HOW AN ALTERNATOR WORKS • A rotor inside a generator is turned by a belt and drive pulley which are turned by the engine. • The magnetic field of the rotor generates a current in the stator windings by electromagnetic induction.

21. 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. HOW AN ALTERNATOR WORKS

22. 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. HOW AN ALTERNATOR WORKS

23. Wye-connected stator winding. • In a wye-type stator connection, the currents must combine because two windings are always connected in series. • 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. HOW AN ALTERNATOR WORKS

24. The current induced in the rotor follows a path that 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. HOW AN ALTERNATOR WORKS

25. Delta-connected stator winding. • The delta winding is connected in a triangular shape. • The delta-connected generator produces lower current at low speed and must be operated at high speed to produce its maximum output. HOW AN ALTERNATOR WORKS

26. ALTERNATOR OUTPUT FACTORS • The output voltage and current of an alternator depend on the following factors. • Speed of rotation • Number of conductors • Strength of the magnetic field A stator assembly with six, rather than the normal three, windings.

27. PRINCIPLES • REGULATOR OPERATION • BATTERY CONDITION AND CHARGING VOLTAGE • TEMPERATURE COMPENSATION ALTERNATOR VOLTAGE REGULATION

28. Regulator controls current through the rotor windings. Typically less than 3 amps. • Simply opens the field circuit if the output voltage exceeds design parameters (example: 14.2 to 14.6 vdc. • Turns on and off at a rate between 10 and 7,000 times per second. ALTERNATOR VOLTAGE REGULATION

29. A typical electronic voltage regulator with the cover removed showing the circuits inside. ALTERNATOR VOLTAGE REGULATION

30. 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. ALTERNATOR VOLTAGE REGULATION

31. Alternators 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 fan • Internal fan(s) • Both an external fan and an internal fan • Coolant cooled ALTERNATOR COOLING

32. Computers can interface with the charging system in three ways. 1. The computer can activate the charging system by turning the field current to the rotor on and off. 2. The computer can monitor the operation of the alternator and increase engine speed if needed during conditions where a heavy load is demanded by the alternator. 3. The computer can control the generator by controlling alternator output to match the needs of the electrical system. COMPUTER-CONTROLLED GENERATORS

33. A typical system used on some General Motors vehicles is called electrical power management (EPM). • It uses a Hall effect sensor attached to the negative battery cable to measure the current leaving and entering the battery. COMPUTER-CONTROLLED ALTERNATORS

34. The amount of time current is flowing through the field (rotor) determines the alternator output. COMPUTER-CONTROLLED ALTERNATORS

35. The output voltage is controlled by varying the duty cycle as controlled by the PCM. COMPUTER-CONTROLLED ALTERNATORS

36. This system has six modes of operation, including: • Charge mode. • Fuel economy mode. • Voltage reduction mode. • Start-up mode. • Battery sulfation mode. • Headlight mode. COMPUTER-CONTROLLED GENERATORS

37. This system has six modes of operation, including: • Charge mode. • Activated with any of the following: • Electric cooling fans on high speed • Rear window defogger on. • Battery state of charge less than 80% • Outside temp < 32 Deg F. • Fuel economy mode. • Voltage reduction mode. • Start-up mode. • Battery sulfation mode. • Headlight mode. COMPUTER-CONTROLLED GENERATORS

38. This system has six modes of operation, including: • Charge mode. • Fuel economy mode. • Reduces load on engine when: • Ambient temperature > 32 deg. F • Battery state of charge > or = 80% • Cooling fans and defogger are off. • Voltage reduction mode. • Start-up mode. • Battery sulfation mode. • Headlight mode. COMPUTER-CONTROLLED GENERATORS

39. This system has six modes of operation, including: • Charge mode. • Fuel economy mode. • Voltage reduction mode. • Reduces stress on battery during low-load: • Ambient temp > 32 deg. F • Battery discharge rate is less ant 7 amps. • Rear defogger off. • Cooling fans on low or off. • Target voltage limited to 12.7 VDC. • Start-up mode. • Battery sulfation mode. • Headlight mode. COMPUTER-CONTROLLED GENERATORS

40. This system has six modes of operation, including: • Charge mode. (activated with any of the following: • Fuel economy mode. • Voltage reduction mode. • Start-up mode. • After engine start: • Sets charging to 14.5 VDC for 30 sec. • After 30 sec. mode is changed to suit conditions. • Battery sulfation mode. • Headlight mode. COMPUTER-CONTROLLED GENERATORS

41. This system has six modes of operation, including: • Charge mode. • Fuel economy mode. • Voltage reduction mode. • Start-up mode. • Battery sulfation mode. • Selected if output voltage is < 13.2 volts for 45 min. • Target voltage is set to 13.9 – 15.5 VDC for 3 min. • After 3 min, system returns to other mode. • Headlight mode. COMPUTER-CONTROLLED GENERATORS

42. This system has six modes of operation, including: • Charge mode. • Fuel economy mode. • Voltage reduction mode. • Start-up mode. • Battery sulfation mode. • Headlight mode. • Selected when headlights are on. • Target voltage is 14.5 VDC COMPUTER-CONTROLLED GENERATORS

43. 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. • Follow the vehicle manufacturer’s recommended procedures to verify proper operation. Tech Tip The Voltage Display Can Be a Customer Concern

44. Alternator 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. SUMMARY

45. How 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? REVIEW QUESTIONS

46. 1. 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 only • Technician B only • Both Technicians A and B • Neither Technician A nor B CHAPTER QUIZ

47. 2. A magnetic field is created in the ________ in an alternator (AC alternator). • Stator • Diodes • Rotor • Drive-end frame CHAPTER QUIZ

48. 3. The voltage regulator controls current through the ________ . • Alternator brushes • Rotor • Alternator field • All of the above CHAPTER QUIZ

49. 4. 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 only • Technician B only • Both Technicians A and B • Neither Technician A nor B CHAPTER QUIZ

50. 5. The alternator output current is produced in the ________ . • Stator • Rotor • Brushes • Diodes (rectifier bridge) CHAPTER QUIZ