CASE STUDY: UNDERSTANDING TIlE PRINCIPLE AND MECHANISM OF ALTERNATOR MOTOR
Brenda Ak Norbert Rabar
I
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
by:
(Project Supervisor)
Judul: Case Study: Understanding the Principles and Mechanism of Alternator 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.
SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan ~I" Malaysia seperti yang termaktub di dalam AKT A RAHSIA RASMI 1972).
D (Mengandungi maklumat TERHAD yang telah ditentukan oJeh
organisasi/badan di mana penyelidikan dijalankan).
TERHAD
(T ANDAT ANGAN PENULIS)
Alamat tetap: NOMBOR 49, JALAN TUNG YEE ?t'"c. .,. M Ally" Dr· ! • .,it, l+o""oIc,.,..,
96100 SARIKEI. SARAWAK. Nama Penyelia
Tarikh: .$. S· :J/!)o s- Tarikh: jiJ I /r
I /o~
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** 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.
DECLARATION
This Project Report is truly my effort except for the attachment portions, which have
been extracted from the stated sources .
./.~......... .
Pusat Khidmal Nd~l~.lCaclel UNIVERSITI MALAYSIA SARAWl
94100 Kota Samaranan
OF AN ALTERNATOR MOTOR
P.KHIDMAT MAKLUMAT AKADEMIK UNIMAS
This project is submitted in partial fulfillment of the requirements
for the Degree of Bachelor of Engineering with Honours
(Mechanical and Manufacturing System Engineering)
Faculty of Engineering
APPRECIATION
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
of this 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.
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Objectives
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 of the 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
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Abstract
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.
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Abstrak
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.
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1.2 What is Alternator Motor
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
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94100 KOla Samarahan
3.2 Bench testing of Alternator
3.2.1 The Dissembling and Identifying The Parts in the Alternator 35
3.2.2 Inspection Process 37
CBAPTER4
4.1.1 Oscilloscope Pattern Test 42
4.1.2 Alternator bench Testing 64
4.2 Discussion 66
Figure 1. 1: The charging system of a vehicle 3
Fig 2.0: Alternator supply voltage to the battery and vehicle's electrical system 5
Figure 2.1 : Alternator's components 6
Figure 2.2: The rotor assembly 8
Figure 2.3: North and South poles of rotor assembly 9
Figure 2.4: Wye connection for stator lead 10
Figure 2.5: Delta connection for stator leads 10
Figure 2.6: Stator windings around the iron core 11
Figure 2.7: Three windings that made an alternator 11
Figure 2.8: Three phase current output 12
Figure 2.9: Diodes 13
Figure 2.1 0: 6-diodes rectifier 14
Figure 2. 11: Voltage Regulator 15
Figure 2.1 2: Brush assembly 16
Figures 2.13 : 4 Steps of alternating current generation using electromagnetic 17
induction .~
Figure 2.15: No voltage is induced 19
Figure 2.16: Armature rotates to 90 degrees, current are produced 19
Figure 2.1 7: Induced voltage decreased 20
Figure 2.1 8: Voltage is induced in negative direction because the 20
conductor cut lines of flux in opposite direction
Figure 2.19: The armature completes one cycle 21
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Figure 2.21 (a) 24
Figure 2.21 (b) 25
Figure 2.23: Resultant direct current voltage after rectification 27
Figure 3.1: Schematic diagram on the devices connection for oscilloscope 35
pattern test ofan alternator
Figure 4.1: Normal pattern of alternator output on scope 44
Figure 4.2: Output waveforms for alternator 1 46
Figure 4.3: Normal pattern of ideal alternator (for comparison purpose) 46
Figure 4.4: Fuji wave pulsating direct current 47
Figure 4.5: Opened/shorted circuit rotor testing 49
Figure 4.6: Slip ring/rotor shaft insulation testing 50
Fig 4.7: Alternator 1 after the repairing 51
Figure 4.8: Alternator 1 voltage output (before repairing) . 52
Fig 4.9: Alternator 1 voltage output (after repairing) 52
Figure 4.10: Normal pattern of alternator (for comparison purpose) 52
Figure 4.11: Output waveforms for alternator 2 54
Figure 4.12: Output waveforms for alternator 3 56
Fig 4.13: Carbon brush in good condition 57
Figure 4.14: Output waveforms for alternator 4 58
Figure 4.15: Output waveforms for alternator 5 62
Figure 4.16: Normal patterns for alternator without load 66
Figure 4.17: Three phase alternalMg direct current 67
Figure 4.18: Full wave rectified direct current 70
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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
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• Trouble-free operation of the alternator is limited primarily by the bearings, slip
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 of these 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 of the car. This is where the alternator comes into the scene.
2
The alternator is that missing link between the petrol and the battery that
generates electricity from the chemical energy by converting the mechanical motion of the
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' (www.misterfixit.com/alterntr.htm) .
..-... ­.. -......-.....
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
name from the type of current it produces which is the alternate current. The alternate
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 of the car .
•
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.
~ radioI horn alternator voltage lights heater generator
starter
electrical system in vehicles
Fig 2.0: Alternator supply voltage to the battery and vehicle's electrical system
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2.1 Construction of alternator
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.
Figure 2.1: Alternator's components
• 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.
2.2.1 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
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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. www.autoshopl 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
interlaced thus the poles alternated north-south around the rotor as can be seen in the
picture ofa rotor below.
(Source: www. www.autoshop 1 0 l.comltrainmoduleslalternator .htm)
2.2.2 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: