CASE STUDY: UNDERSTANDING TIlE PRINCIPLE AND MECHANISM OF ALTERNATOR MOTOR

Transcription

1 CASE STUDY: UNDERSTANDING TIlE PRINCIPLE AND MECHANISM OF ALTERNATOR MOTOR Brenda Ak Norbert Rabar TL Bachelor of Engineering with Honours (Mechanical Engineering and Manufacturing Systems) 2005

2 APPROVAL SHEET This project report, which entitled "Case Study: Understanding the Principle and Mechanism 0/ Alternator Motor", was prepared by Brenda ak Norbert Rabar as a partial fulfilhnent for the Bachelor's Degree of Engineering with Honours (Mechanical and Manufacturing System Engineering) is hereby read and approved Prof. Madya Dr. Sinin Bin Hamdan (Project Supervisor) Date: t(1r&s --"--I--{---""-1-(-

3 BORANG PENYERAHAN TESIS Judul: Case Study: Understanding the Principles and Mechanism ofalternator Motor SESI PENGAJlAN: 2004/2005 Saya BRENDA AK NORBERT RABAR mengaku membenarkan tesis ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut: 1. Hakmilik kertas projek adalah di bawah nama penulis melainkan penulisan sebagai projek bersama dan dibiayai oleh Universrti Malaysia Sarawak, hak miliknya adalah kepunyaan Universlti Malaysia Sarawak. 2. Naskah salinan di dalam bent uk kertas atau mikro hanya boleh dibuat dengan kebenaran bertulis daripada. Universiti Malaysia Sarawak atau penulis. 3. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan untuk pengajian mereka. 4. Kertas projek hanya boleh diterbitkan dengan kebenaran penulis atau Universiti Malaysia Sarawak. Bayaran royalti adalah mengikut kadar yang dipersetujui kelak. 5. * Saya membenarkanltidak membenarkan Perpustakaan membuat salinan kertas projek ini sebagai bahan pertukaran di antara institusi pengajian tinggi. 6. ** Sila tandakan (f) di mana kotak yang berkenaan. ~I SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan " Malaysia seperti yang termaktub di dalam AKT A RAHSIA RASMI 1972). D TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan ojeh organisasi/badan di mana penyelidikan dijalankan). W TIDAK TERHAD 7 (T ANDAT ANGAN PENULIS) Alamat tetap: NOMBOR 49, JALAN TUNG YEE Tarikh:.$. S :J/!)o s- Catatan?t'"c..,. M Ally" Dr!.,it, l+o""oic,.,.., SARIKEI. SARAWAK. Nama Penyelia Tarikh: jij I /ri/o~ Potong yang tidak berkenaan ** Jika Kertas Projek ini SUUT atau TERHAD, sila lampirkan surat daripada pihak berkuasalorganisasl berkenaan dengan menyertakan sekali tempoh kertas projek. lni perlu dikelaskan sebagai SULIT atau TERHAD.

4 DECLARATION This Project Report is truly my effort except for the attachment portions, which have been extracted from the stated sources../.~.... (Brenda ak Norbert Rabar) Certified by, (prof. Madya Dr. Sinin Hamdan) Date:

5 CASE STUDY: UNDERSTANDING THE PRINCIPLES AND MECHANISM OF AN ALTERNATOR MOTOR P.KHIDMAT MAKLUMAT AKADEMIK UNIMAS Brenda ak Norbert Rabar This project is submitted in partial fulfillment ofthe requirements for the Degree of Bachelor of Engineering with Honours (Mechanical and Manufacturing System Engineering) Faculty of Engineering UNIVERSITI MALAYSIA SARA WAK 2005

6 For my loving family II

7 First of all, I would like to express my sincere thanks to all good people who provide information, guidance, assistance and co-operation during the preparing and completing ofthis project report. 1 would like to express a heartfelt thanks to my supervisor, Prof Madya Dr. Sinin Hamdan for his guidance, advised and time in supervising me during the completion of this project. I would also like to thank Mechanical Engineering and Manufacturing System lab assistants, Mr. Masri and Mr. Rhyier for their help and assistant especially concerning the use of Mechanical laboratory for all the time I had try to finish the project. Last but not least, I would like to express my gratitude to my family for their support and encouragement all this time. Thank you. 111

8 The project report was a compulsory subject, which has to be done by the student as a pre-requisite to graduate in Bachelor Degree (BSc) in Mechanical Engineering and Manufacturing System. Below are the objectives ofthe project report: There are 3 objectives of this project. They are: [J To investigate the faults! the malfunction ofalternator through Oscilloscope Pattern Test Bench Testing [J To repair the faulty alternators so that they could be used again [J To gain the understanding on the principle and mechanism ofalternator lv

9 Basically, this project report is describing about the principles and working mechanism of alternator motor. The detail on how the electricity is produced by alternator motor was explained in this report. The explanation also includes the description and function of each component inside the alternator. This report also explains and investigates how to detect and identify the faults of alternator through the oscilloscope pattern testing and bench testing. The data gathered through both the testing are use to compare with theory and then they are documented in this report. v

10 Secara asasnya projek ini menerangkan tentang prinsip and mekanisme kerja bagi ahernator motor. Penerangan yang terperinci tentang bagaimana elektrik dihasilkan oleh alternator motor juga diterangkan. Penerangan tersebut juga merangkumi deskripsi dan juga fungsi setiap komponen yang terdapat di dalam alternator motor. Projek ini juga menerangkan bagaimana kita dapat menyiasat tentang kerosakan yang berlaku di dalam ahemator melalui ujian dengan osiloskop dan 'bench testing'. Data yang did apat i dikumpul dan kemudiannya dijilid di dalam laporan ini. VI

11 TABLE OF CONTENT APPRECIAnON OBJECTIVES ABSTRACT ABSTRAK LIST OF FIGURES LIST OF TABLES 1Il IV V VI IX XI CHAPTERl INTRODUCTION 1. 1 History of Alternator Motor 1.2 What is Alternator Motor 1 2 CHAPTER 2 LITERATURE REVIEW 2. 1 Fundamental of Alternator.:. 2.2 The Components of an Alternator 2.3 The Operating Principles of Alternator 2.4 Current Research on Alternator Vll

12 METHODOLOGY 3.1 Oscilloscope pattern tests ofalternator Bench testing ofalternator The Dissembling and Identifying The Parts in the Alternator Inspection Process Assembly ofalternator 40 CBAPTER4 FINDINGS AND DISCUSSION 4.1 Detection and Identification ofthe Alternator's fault Oscilloscope Pattern Test Alternator bench Testing Discussion 66 CHAPTERS CONCLUSION AND RECO MENDATION 5.1 Conclusion Recommendation 72 BIBLIOGRAPHY APPENDIX VllI

13 LIST OF FIGURES Figures Page Figure 1. 1: The charging system of a vehicle Fig 2.0: Alternator supply voltage to the battery and vehicle's electrical system Figure 2.1 : Alternator's components Figure 2.2: The rotor assembly Figure 2.3: North and South poles of rotor assembly Figure 2.4: Wye connection for stator lead Figure 2.5: Delta connection for stator leads Figure 2.6: Stator windings around the iron core Figure 2.7: Three windings that made an alternator Figure 2.8: Three phase current output Figure 2.9: Diodes Figure 2.1 0: 6-diodes rectifier Figure 2. 11: Voltage Regulator Figure 2.1 2: Brush assembly Figures 2.13: 4 Steps of alternating current generation using electromagnetic induction.~ Figure 2. 14: Components that produced current Figure 2.15: No voltage is induced Figure 2.16: Armature rotates to 90 degrees, current are produced Figure 2.1 7: Induced voltage decreased Figure 2.1 8: Voltage is induced in negative direction because the conductor cut lines of flux in opposite direction Figure 2.19: The armature completes one cycle IX

14 Figure 2.20: A diagram on alternator side Figure 2.21 (a) Figure 2.21 (b) Figure 2.22: Three phase sine-wave alternating current Figure 2.23: Resultant direct current voltage after rectification Figure 3.1: Schematic diagram on the devices connection for oscilloscope pattern test ofan alternator Figure 4.1: Normal pattern of alternator output on scope Figure 4.2: Output waveforms for alternator 1 Figure 4.3: Normal pattern of ideal alternator (for comparison purpose) Figure 4.4: Fuji wave pulsating direct current Figure 4.5: Opened/shorted circuit rotor testing Figure 4.6: Slip ring/rotor shaft insulation testing Fig 4.7: Alternator 1 after the repairing Figure 4.8: Alternator 1 voltage output (before repairing). Fig 4.9: Alternator 1 voltage output (after repairing) Figure 4.10: Normal pattern of alternator (for comparison purpose) Figure 4.11: Output waveforms for alternator 2 Figure 4.12: Output waveforms for alternator 3 Fig 4.13: Carbon brush in good condition Figure 4.14: Output waveforms for alternator 4 Figure 4.15: Output waveforms for alternator 5 Figure 4.16: Normal patterns for alternator without load Figure 4.17: Three phase alternalmg direct current Figure 4.18: Full wave rectified direct current x

15 LIST OF TABLES Tables Page Table 4.1 : Current between two slip rings Table 4.2: Current between two slip rings Table 4.3: Result on alternator bench testing Xl

16 INTRODUCTION 1.1 History of an alternator motor In the 60s. the older model car used to use generators. Those generators produce direct current to empower the battery. Thus direct current (DC) charging system was used on older model cars until the increasing number of electrical components and increased currents requirements were no longer satisfied by it. Thus the alternating current generator (Ae) or alternator replaced the direct current generator to satisfy the increased current requirement. The alternator has several advantages over the older OC generator: An alternator can generate power up to one-third of its output when the engine is idling.. Diode rectifiers are not subject to wear as the commutators and brushes in a dc generators Diode isolate the alternator from feedback from the battery should alternator voltage drop below battery voltage. The dc generator cutout relay was trouble prone Alternators are lighter than dc generators of the same capacity 1

17 rings and brushes, which carry only a small current and are under very light spring pressure 1.2 What is an alternator motor? When we are in the car, does anyone ever realize that we enjoyed the comfort of an air-conditioning fan, stereo and lights? We can enjoyed these comfort because a car has an electrical system that carry power not only to the stereo and air-conditioning but also to the headlights, ignition coils and engine cooling fans. Have we ever realized where we get the electrical energy to support all ofthese luxuries? Of course some of us might say that we get this energy from the battery. It is common knowledge that battery supplied electrical energy that enable us to have air-conditioning and able to listening to the stereo. But, a battery like the battery of our hand phone also needs charging because the battery cannot generate the electricity to restore the one that had been use up. Thus, this electricity did not come from the battery alone, and to be exact the energy originated from petrol. How is the car ~!ng to convert the chemical energy from the petrol into electrical energy to be use by the car electrical system? So, there must be something that can generate electricity from the petrol to power the battery and then in tum will powers up the electrical system ofthe car. This is where the alternator comes into the scene. 2

18 generates electricity from the chemical energy by converting the mechanical motion ofthe engine into electrical energy that can be use by the battery to power up the electrical system ofthe car. In short, alternator charges battery. This explanation is further expressed in a website, I quoted, 'the alternator will be tum on by the mechanical power from the crankshaft and then it will convert the power from the gasoline engine in the gas tank to electrical energy to keep the battery restored' ( Figure 1.1: The charging system ofa vehicle Alternator is a part of ~1ucle charging system. In fact, alternator is the heart of charging system. This is because the alternator produced the voltage to keep the battery running. The charging system is consisted of battery, alternator, drive belt, the voltage regulator, charge indicator, ignition switch, cables and the-wiring. In older model cars in the 60s, they used to use generators that produce direct current to empower the battery. But now, cars use alternator that produce alternate current and thus, the alternator get its 3

19 current produce by the alternator will be changed into direct current because the battery could only used direct current and not alternate current. When we started the car or when engine ignition started, the current use will made the battery drain and thus, the alternator will react quickly to supply the high load demands required of the electrical system. So, the alternator will generate current for two purpose which are to replace or restore the reserve electron in a battery and to operate all of the electrical accessories while the engine running. Thus, when the engine is running the alternator will generate the current needed but when the engine is not running, the battery could take care of the electrical demands ofthe car. 4

20 CHAPTER TWO LITERA TURE REVIEW 2.0 The fundamental of alternator Alternator is a part of charging system. Alternator is exactly an alternating current (AC) generator driven by engine power to produce electricity. The alternating current produced by the alternator is then being converted to the direct current. The direct current will be used to charge the battery and provide the electrical needs of the vehicle. battery n I I I ~ I horn radio alternator voltage lights heater generator starter electrical system in vehicles Fig 2.0: Alternator supply voltage to the battery and vehicle's electrical system 5

21 2.1 Construction ofalternator Most of the regulators now are built inside of the alternator, unlike older model regulators which are design with externally mounted regulators. For the most part alternators are design so that it was easily serviced from the rear. Alternators are generally designed to be compact and lightweight. The front and rear alternator housing are usually constructed of die-cast aluminu"!. Needle- or bali-type bearings are used to produce a low friction surfaced for the rotor shaft. Cooling for the alternator is most often provided by a fan mounted on the front of the rotor shaft. The rotating fan draws the cooling air through and over the alternator to prevent overheating of the windings and diodes be components of an alternator Figure 2.1: Alternator's components 6

22 There are 5 basic components of alternator. They are: Rotor Stator coil Rectifier assembly Vohage regulator Brush assembly Beside the 5 basic components that are going to be discussed in depth in this chapter, there are also the support components that exist in the alternator to make the assembly possible. They are the key, pulley, fan, bearing, bearing retainer plate, space ring, snap ring, brush holder brush spring, terminal insulator, collar, drive end frame, feit ring, felt cover, bracket, insulation washer and insulator. The location and function of each and every component will be explored as we go along the report Rotor Rotor is fitted inside the stator. Rotor and stator are two main components that play an important role in the producing the voltage of the alternator. First, we will explore the components that rotor are made up of. Rotor consists of 7 main components IIld they are the iron core or also known as the rotor shaft, rotor field windings, finger poles, slip rings, internal cooling fan and the bearings. The basic components that made up a rotor are an iron core or also known as rotor shaft and wounded around the iron 7

23 core is the coil winding and two claw-shaped finger pole pieces. At the end of the iron core, there are two slip rings. Some mode} of alternator includes support bearings and one or two internal cooling fans. The whole components of the rotor win be supported by two bearings. One of these bearings is located on the rotor shaft and the other is in the drive frame. Figure 2.2: The rotor assembly (Source: www. 0 I.com/trainmodules/alternator.htm) The coil winding around the iron core is made of copper wire. This copper wire will make several turns around the iron core to create the copper wire cob winding. The copper wire cot! winding is known as Rotor Field Windings. There are two ends of rotor field winding and the ends are both connected to the slip rings. The brushes will be connected to the slip rings and these brushes are the components that will connect the rotor to the alternator. At both ends of the windings there are metal plates bents over it. The metal plates are known as the finger poles. These poles are not touching each other but rather they are interlaced. The poles will take on the polarity of the side of the copper coil windings they are bent over either north or south. Because the poles are 8

24 interlaced thus the poles alternated north-south around the rotor as can be seen in the picture ofa rotor below. Figure 2.3: North and South poles of rotor assembly (Source: www l.comltrainmoduleslalternator.htm) Stator coil The stator assembly is made with three sets of windings. Basically stator assembly is IOIde up of a circular stato," core with copper wire windings will be wrap around it. There are 3 sets of winding that are wrapped in slots around a laminated, circular iron &arne as mentioned before. These windings are also evenly spaced around the iron &arne. Each group of windings has two leads and this means there are six leads for three windings. The function of the leads is to let the current to come in and out. The first lead is for the current entering the winding and the second lead is for current leaving. There are two method ofconnecting the leads: 9