design improvements of 12 slot-14 pole hybrid excitation flux
TRANSCRIPT
DESIGN IMPROVEMENTS OF 12 SLOT-14 POLE HYBRID EXCITATION
FLUX SWITCHING MOTOR WITH 1.0KG PERMANENT MAGNET FOR
HYBRID ELECTRIC VEHICLES
NOR ADILLAH BINTI AHMAD MAZLAN
A project report submitted in partial
fulfillment of the requirement for the award of the
Degree of Master Electrical Engineering
Faculty Of Electric And Electronic Engineering
Universiti Tun Hussein Onn Malaysia
JULY 2014
v
ABSTRACT
Flux switching machine (FSMs) is a new class of brushless motor used in the
automotive industry and have been developed in recent years. The FSMs can be
divided into three groups which are permanent magnet flux switching machine
(PMFSM), field excitation flux switching machine (FEFSM) and hybrid excitation
flux switching machine (HEFSM). Among these three groups, HEFSM has several
attractive features and offers the advantages of robust rotor structure together with
variable flux control capabilities. These advantages make this machine more
attractive to apply for high-speed motor drive system. This project is a design
improvements of 12 slot- 14 pole hybrid excitation flux switching machine (HEFSM)
with 1.0 kg permanent magnet (PM) for hybrid electric vehicles(HEVs). The design
target of maximum torque is 333Nm, a maximum power of more than 123kW, and a
maximum power density of more than 3.5kW/kg. The performance of the proposed
machine on the initial design and improvements design are analysed based on 2-D
Finite element analysis (FEA). The final results prove that the final design HEFSM is
able to keep the maximum torque when compared to the initial design HEFSM.
vi
ABSTRAK
Motor Pensuisan Fluks (FSMs) adalah motor berkelas yang digunakan dalam industri
automotif yang baru dan telah dibangunkan dalam tahun kebelakangan. FSMs ini
boleh dibahagikan kepada tiga kumpulan iaitu Motor Pensuisan Fluks Magnet Kekal
(PMFSM), motor pensuisan fluks pengujaan medan (FEFSM) dan motor pensuisan
fluks pengujaan hybrid (HEFSM). Antara ketiga-tiga kumpulan ini, HEFSM
mempunyai beberapa ciri-ciri yang menarik dan menawarkan kelebihan struktur
rotor teguh bersama dengan keupayaan kawalan pembolehubah sentiasa berubah-
ubah. Kelebihan ini menjadikan mesin ini lebih menarik untuk diaplikasikan pada
sistem pacuan motor yang berkelajuan tinggi. Projek ini adalah penambahbaikan
kepada reka bentuk 12 slot-14 pole motor pensuisan fluks pengujaan hybrid
(HEFSM) dengan magnet kekal 1.0 kg (PM) untuk pengangkutan elektrik hybrid
(HEVs). Sasaran reka bentuk adalah tork maksimum adalah 333Nm, kuasa
maksimum lebih daripada 123kW, dan ketumpatan kuasa maksimum lebih daripada
3.5kW / kg. Prestasi mesin yang dicadangkan ini untuk reka bentuk awal dan
rekabentuk penambahbaikan akan dianalisis menggunakan 2-D finite element
analisis (FEA). Keputusan akhir menunjukkan bahawa rekabentuk penambahbaikan
dapat menjana tork maksimum yang lebih tinggi berbanding rekabentuk awal.
vii
CONTENTS
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
CONTENTS vii
LIST OF FIGURES x
LIST OF TABLES xii
LIST OF ABBREVIATIONS AND SYMBOLS xiv
CHAPTER 1 INTRODUCTION 1
1.1 Project Background 1
1.2 Problem Statement 3
1.3 Objectives 5
1.4 Scopes 5
viii
CHAPTER 2 OVERVIEW OF FLUX SWITCHING
MACHINES (FSMs)
6
2.1 Introduction 6
2.2 Classifications of Flux Switching 7
Machine (FSM)
2.3 Permanent Magnet Flux Switching 7
Machine (PMFSM)
2.4 Field Excitation Flux Switching 9
Machine (FEFSM)
2.5 Hybrid Excitation Flux Switching 12
Machine (HEFSM)
CHAPTER 3 METHODOLOGY 19
3.1 Design Restrictions and 19
Specifications
3.2 Flowchart of Project 24
3.3 JMAG Designer Software 25
3.4 Design Methodology for improvements 37
3.4.1 Parameter sensitivity of the simplified 37
design
CHAPTER 4 DATA ANALYSIS AND RESULT 41
4.1 Initial result of the proposed HEFSM 41
4.1.1 No- load analysis 42
4.1.1.1 12 and 3Coil Tests 42
4.1.1.2 UVW test 45
ix
4.1.1.3 Cogging Torque and Flux Strengthening 48
4.1.1.4 Flux Line and Flux Distributions 50
4.1.2 Load Analysis 52
4.1.2.1 Torque and power versus Je 53
at various Ja
4.1.2.2 Torque and power versus 59
speed characteristics
4.2 Result and performances of the 60
improvements design 12S-14P HEFSM
4.2.1 Torque versus Ja at various Je 60
4.2.2 Torque and power versus speed 62
characteristics
4.2.3 Flux density distribution and flux path 64
of final improvement design
4.2.4 Weight of machine 67
CHAPTER 5 CONCLUSION 69
5.1 Conclusion 69
5.2 Future Work 70
REFERENCES 71
x
LIST OF FIGURES
1.1 Cross sections of traction motors 2
2.1 Classification of flux switching machine (FSMs) 7
2.2 3-phase PMFSMs 8
2.3 Operation principle of PMFSM 9
2.4 (a) 1-phase 4S-2P FEFSM (b) 3-phase 12S-8P 10
2.5 12S-10P FEFSM 11
2.6 Principle operation of FEFSM 12
2.7 Various stator slot and rotor pole of HEFSM 13
2.8 The operating principle of the proposed HEFSM 14
2.9 Original design of 12S-10P HEFSSM 16
2.10 Improved design of 12Slot-10Pole HEFSSM with 1.0kg
permanent magnet
16
2.11 Design parameter defined as D1 to 17
3.1 Main machine dimension of the proposed HEFSM for
HEV applications
20
3.2 Design parameter defined as D1 to D10 23
3.3 General flow diagram of deterministic design approach 23
3.4 Flowchart of project 24
3.5 Flowchart to design machine by using JMAG designer. 25
3.6 Design of 14-Pole rotor 27
3.7 Design of 12-Slot rotor 29
3.8 Armature coil 31
3.9 12 Permanent Magnet 33
xi
3.10 Field Excitation Coil (FEC) 34
3.11 Full design of 12 Slot-14 Pole HEFSM 35
3.12 UVW circuit Implementation 35
3.13 FEC circuit implementation 36
3.14 Design parameter defined as D1 to D10 37
3.15 Torque versus rotor radius, D1 38
3.16 (a) Torque versus rotor pole width, D2 (b) Torque
versus rotor pole depth, D3
38
3.17 (a) Torque versus rotor pole width, D2 (b) Torque
versus rotor pole depth, D3
39
4.1 Result of 12 coil test 42
4.2 The maximum flux of 12 coil test 43
4.3 The result of 3 coil test 44
4.4 Zero rotor position 44
4.5 Winding arrangement of FEC coil 45
4.6 UVW test for PM only 46
4.7 UVW test for FEC only 46
4.8 UVW test for PM+FEC 47
4.9 Comparison of U-phase Flux linkages 47
4.10 Cogging torque result 48
4.11 U-phase flux linkage at various DC FEC current
densities
49
4.12 The result of flux strengthening 50
4.13 Flux lines of the machine 51
4.14 Flux distributions of the machine 52
4.15 Instantaneous torque profile at Ja = 30Arms/mm2, Je =
30A/mm2
53
4.16 Torque versus Je at various Ja 54
4.17 Power versus Je at various Ja 54
4.18 Flux vector diagram at Ja = 30Arms/mm2 56
4.19 Flux path diagram at Ja = 30Arms/mm2 58
xii
4.20 Torque and power vs speed 59
4.21 Instantaneous torque profile at Ja = 30Arms/mm2, Je =
30A/mm2
60
4.22 Instantaneous torque profile of Initial and Final Design 61
4.23 Torque versus Je at various Ja 62
4.24 Torque and power vs speed of final design 63
4.25 Torque vs speed of final design 63
4.26 Flux vector diagram of final design at Ja = 30Arms/mm2 65
4.27 Flux path of the final design at open circuit condition 66
xiii
LIST OF TABLES
2.1 HEFSSM Design Restrictions And Specifications For
Hybrid Electric Vehicle Applications
15
2.2 Initial And Final Design Parameters Of 12slot-10pole
HEFSSM For HEV Applications
17
2.3 Performance Comparison of Finally Designed 12Slot -
10Pole HEFSSM For HEV Applications
18
3.1 Design restrictions and specifications of the proposed
12S-14P HEFSM
21
3.2 Initial design parameters of 12S-14P HEFSM 22
4.1 Estimated weight, power and torque density of initial and
final design HEFSM
67
4.2 Initial and final design parameters of 12S-14P HEFSM 68
xiv
LIST OF SYMBOLS AND ABBREVIATIONS
BRICs Brazil, Russia, India, China and South Africa
EV Electric Vehicles
FEC Field Excitation Coil
FEFSM Field Excitation Flux Switching Machine
FSM Flux-switching Machine
FSPM Flux-switching permanent magnet
HEFSM Hybrid Excitation Flux Switching Motor
HEV Hybrid Electric Vehicles
ICE Internal Combustion Engine
IM Induction Motor
IPMSM Interior Permanent Magnet Synchronous Motor
kW Kilo- Watt
mm Milimeter
Nm Newton metre
PM Permanent Magnet
PMFSM Permanent Magnet Flux Switching Machine
r/min Revolutions Per Minute
1
CHAPTER 1
INTRODUCTION
This chapter introduces the idea and concept of the project. It consists of project
background and the overview of the project.
1.1 Project Background
Conventional internal combustion engine (ICE) was equipped in vehicles and
have been used as a personal transportation for over 100 years. As demand of the
private vehicles are also increasing due to the rates of world population. This trend
will only intensify with the catching up of developing countries like BRICs [1]. The
main problems due to these demands are related to emissions, fuel economy and
global warming. Also the prices of fossil fuels keep rising. The greenhouse effect,
also known as global warming, is an issue that all people have to face. This matter
encouraged people to look at EV’s as a possible alternative mode of transportation as
well as the cost and limitations supply of gasoline products.
Electric vehicles have been existence for a very long time. Electric vehicles give
very low acoustic noise and zero emissions. The propulsion system for electric
2
vehicles consists of batteries, electric motors with drives, and transmission gears to
wheels.
At present, the major types of electric motors under serious consideration for
HEVs as well as for EVs are the dc motor, the induction motor (IM), the permanent
magnet synchronous motor (PMSM), and the switched reluctance motor (SRM).
Based on the exhaustive review on state of the art of electric-propulsion systems, it is
observed that investigations on the cage IMs and the PMSMs are highly dominant,
whereas those on dc motors are decreasing but SRMs are gaining much interest. Due
to the large torque capability and high torque (power) density, Flux-switching
permanent magnet (FSPM) machines have attracted considerable attention in recent
years, as well as compact and robust structure since both the locations of magnets
and armature windings are located in stator instead of rotor as those in the
conventional rotor-PM machines [3].
a) b)
Figure 1.1: Cross sections of traction motors (a) PM brushless motor (b) switch
reluctance motor
This project deals with a design optimization of hybrid excitation flux switching
motor (HEFSM) with 0.4kg permanent magnet. Among various types of HEFSSM,
the machine with both permanent magnet (PM) and field excitation coil (FEC) on the
stator has the advantages of robust rotor structure together with variable flux control
3
capabilities that make this machine becoming more attractive to apply for high-speed
motor drive systems.
However, for solely PMs excited machines, it is a traditional contradiction
between the requests of high torque capability under the base speed (constant torque
region) and wide speed operation above the base speed (constant power region).
Hence, hybrid-excitation flux-switching machines (HEFSM) are proposed in which
the magnet dimensions were reduced to save room for the introduced field excitation
coil (FEC) windings. It is obvious that with variable dc FEC, the air gap field of
HEFSM can be easily controlled and is favorable for Electric Vehicle (EV)
applications [4].
1.2 Problem statement
With the issue of the global warming become an important issue in the 21st
century, it concerns about environmental protection and energy conservation where
carbon dioxide (CO2) gas emissions should be reduced to maintain the air quality.
With the advent of more stringent regulations related to emissions, fuel economy,
and global warming, as well as energy resource constraints, electric, hybrid, and fuel-
cell vehicles have attracted increasing attention from vehicle manufactures,
governments, and consumers. The demand toward vehicles for personal
transportation has increased due to the increase of world population. To maintain and
develop these energy consuming technologies, availability of sustainable energy
sources and their effective utilization through efficiency improvements are of
paramount importance. This increase has mainly come from new demands for
personal-use vehicles powered by conventional internal combustion engines (ICEs)
[1]. Government agencies and organizations have developed more stringent
standards for fuel consumption and emissions due to the environmental problems.
Oil consumption of the transportation sector has grown at a higher rate than any
other sector in these decades. The prices of oil also continue increase dramatically
while tougher regulations and policies on permitted exhaust gasses are being
instituted in major cities of the world. These related issues are compelling vehicle
4
manufacturers to come up with fuel efficient vehicles that called hybrid electric
vehicles. Electric (battery) vehicles exist for a long time and give very low acoustic
noise and zero emissions. One of the most valuable achievements in power
electronics is to introduce degree of freedom to variable frequency from the fixed
value of the generated electrical power supplies. Over 60% of the generated energy is
consumed by electric motors. Variable speed drive, which regulates the speed of the
motor by controlling the frequency, can significantly reduce the energy consumption,
particularly in heavy-duty systems. Thus, improvements in efficiency of the drive
systems are the most effective measures to reduce primary energy consumption, and
thereby reduce CO2 gas emissions which cause global warming [5-6].
The complex management of power distribution which required for hybrid
electric vehicle (HEV) with two power sources of engine and battery is not needed
because of the power source of HEV is only battery. In addition, most of commercial
HEV used single motor and transmission gears coupled to the wheels. This system
composed of many components and lead to transmission losses and also less
efficiency and reliability. To enable HEV to directly compete with gasoline vehicles,
an electric motor installed on HEV aims to pursue high-efficiency, high power and
torque density, high controllability, wide speed range and maintenance-free
operation, thus reducing the gas emissions. [7].
To meet this challenge, many automotive companies have been commercializing
HEV, in which IPMSM using rare-earth magnet has been employed as their main
traction drives. This is due to the restriction of motor size to ensure enough passenger
space and the limitation of motor weight to reduce fuel consumption [7]. Although
the torque density of each motor has been hardly changed, a reduction gear has
enabled to elevate the axle torque necessary for propelling the large vehicles such as
RX400h and GS450h [7]. From this trend, IPMSM design tends to be difficult
because all PMs used in IPMSM are on the rotor part and hence, to ensure the
mechanical strength of rotor relies on the number of bridges and rib thickness
between PMs. Therefore, this researches and developments on a new machine with
high power density, robust rotor structure for high-speed operation, and with no or
less-rare-earth magnet machines would be very important [7].
5
1.3 Objectives
The objectives of this project are:
i) To design improvements of 12 slot-14 pole hybrid excitation flux
switching motor synchronous machine (HEFSSM) with 1.0kg permanent
magnet
ii) To analyze performances of the design motor under no load, load and
torque speed.
iii) To improve the initial design of 12 Slot-14 Pole until the performances
are achieved.
1.4 Scopes
The scopes of the project are:
i) Design by using software JMAG Designer version 13.0
ii) The outer diameter, the motor stack length, the shaft radius and the air gap of
the main part of the machine design being 264mm, 70mm, 30mm and 0.8mm.
iii) Electrical restriction to field excitation current density(Je), armature current
density (Ja) and the limit of the current density is set to the maximum of 30
Arms/mm2 for armature winding and 30 A/mm
2 for FEC. The armature coil
current (Ia) is set to 360A/mm2.
6
CHAPTER 2
OVERVIEW OF FLUX SWITCHING MACHINES (FSMs)
2.1 Introduction
Flux switching machine is a new class of brushless motor as an alternative to
the permanent magnet brushed motor used in the automotive industry. It is the
combination of switch reluctance machine (SRM) and synchronous machine. This
new flux switching motor is a very simple motor to manufacture and coupled with a
power electronic controller and requiring only two power semiconductor switches. It
has the potential to be extremely low cost in high volume applications. The
advantages of this machine are high-power density and relative high efficiency in a
smaller and lighter package. Another advantage is the simplicity of the rotor, which
allows for easy manufacture and attainment of relatively high speeds in operation.
The shape of the rotor is designed to present a variable reluctance to the windings on
the stator as it rotates, modulating the flux in defined sections of the stator to produce
bipolar AC flux linkages of the armature windings. The FSM incorporates the
features of a conventional switched reluctance (SR) machine and a conventional dc
machine.
7
2.2 Classifications of Flux Switching Machine (FSM)
The FSMs can be divided into three groups which are permanent magnet flux
switching machine (PMFSM), field excitation flux switching machine (FEFSM) and
hybrid excitation flux switching machine (HEFSM). PMFSM and FEFSM has only
PM and field excitation coil (FEC) as their main flux sources. HEFSM combines
both PM and FEC as main flux sources. Figure 2.1 below, illustrates the
classifications of FSMs.
Figure 2.1: Classification of flux switching machine (FSMs)
2.3 Permanent Magnet Flux Switching Machine (PMFSM)
Development of Permanent Magnet Flux Switching Machines (PMFSM) for
electric vehicle applications has gained popularity. The principle of PMFSM has
been studied for several decades. Both permanent magnets and armature windings
are located in the stator in PMFSM and a robust rotor similar to that of Switched
Reluctance Machines (SRM) is employed. The permanent magnet flux switching
(PMFS) machine is a less common type of PM machines comprising a passive and
Flux Switching Machines
(FSMs)
Field Excitation
(FE) FSM
Permanent Magnet
(PM) FSM
Hybrid Excitation
(HE) FSM
8
robust salient-pole rotor and a complex salient-pole stator with armature windings
and permanent magnets.
Figure 2.2 shows a typical 6S-5P PMFSM and 12S-10P PMFSM. The
concentrated windings employed in the PMFSM are also similar to those in the SR
motor. In the PMFSM machine a concentrated coil is wound around two adjacent
teeth with a piece of permanent magnet (PM) between them, and the two teeth and
the magnet form a stator pole. This leads to low copper consumption and low copper
loss due to the short end-windings. The magnets are tangentially magnetized, with
the opposite direction in the adjacent magnets. Therefore, the number of stator poles
must be even, and also must be integral times 3 for the 3-pole PMFSM.
The stator armature winding consists of concentrated coils and each coil
being wound around the stator tooth formed by two adjacent laminated segments and
a magnet. In the same figure, all armature coil phases such as A1, B1, C1, A2, B2
and C2 have the same winding configuration and are placed in the stator core to form
12 slots of windings. The slot area is reduced when the magnets are moved from the
rotor to the stator, it is easier to dissipate the heat from the stator and the temperature
rise in the magnet can be controlled by proper cooling system.
a) 6S- 5P b) 12S- 10P
Figure 2.2: 3-phase PMFSMs
The general operating principle of the PMFSM is illustrated in Fig. 2.3,
where the black arrows show the flux line of PM as an example. The PM flux which
is linked in the coil goes out of the coil and into the rotor tooth in figure 2.3 (a) then
9
the flux-linkage corresponds to one polarity. The PM flux goes out of the rotor tooth
and into the stator tooth when the rotor moves forward to the direction in Fig. 2.3 (b),
keeping the same amount of flux-linkage whilst reversing the polarity. Consequently,
as the rotor moves, the flux-linkage in the windings will change periodically, and
back-EMF will be induced. Both the PM flux-linkage and back-EMF can be
sinusoidal versus the rotor position as long as the machine is properly designed, thus
it can be driven in the blushless ac (BLAC) mode.
Figure 2.3: Operation principle of PMFSM
The problem of such kind of machine is the rotor mechanical strength which
needs to be considered if the machine is applied for high speed applications. In
addition, the summary of various types of PMFSMs are also discussed in [8].
2.4 Field Excitation Flux Switching Machine (FEFSM)
The PM excitation on the stator of conventional PMFSMs can be replaced by
DC FEC to form FEFSMs. Various types of FEFSM are shown in figure 2.4. The
machine consists of only field excitation coil (FEC) and armature coil allocated on
the stator part. The rotor consists of only single piece iron, becoming more robust
and more suitable for high speed operation. The concept of the FEFSM involves
changing the polarity of the flux linking with the armature coil windings, with
respect to the rotor position. Both armature coil and FEC windings are placed in the
stator which overlapped each other as seen in a figure. The novelty of the invention
10
is that the single-phase ac configuration could be realized in the armature windings
by deployment of DC FEC and armature winding, to give the required flux
orientation for rotation. The torque is produced by the variable mutual inductance of
the windings.
(a) (b)
Figure 2.4: (a) 1-phase 4S-2P FEFSM (b) 3-phase 12S-8P
The term flux switching is to describe machines in which the stator tooth flux
switches polarity following the motion of a salient pole rotor. All excitation sources
are located on the stator with the armature coils and FECs allocated to alternate stator
teeth. In the 12Slot-10Pole machine, the FECs produce six north poles interspersed
between six south poles. The three-phase armature coils are accommodated in the 12
slots for each 1/4 stator body periodically. The fluxes generated by mmf of FECs link
with the armature coil alternately as the rotor rotates. For the rotor rotation through
1/10 of a revolution, the flux linkage of the armature has one periodic cycle and thus,
the frequency of back-emf induced in the armature coil becomes ten times of the
mechanical rotational frequency.
11
Figure 2.5: 12S-10P FEFSM
The operating principle of the FEFSM is illustrated in Figure 2.6. The
direction of the FEC fluxes into the rotor shown in Fig. 2.6 (a) and (b) while Fig. 2.6
(c) and (d) illustrate the direction of FEC fluxes into the stator which produces a
complete one cycle flux. The flux linkage of FEC switches its polarity by following
the movement of salient pole rotor which creates the term “flux switching” similar as
PMFSM. Each reversal of armature current shown by the transition between Fig.
2.6(a) and (b), will cause the stator flux to switch between the alternate stator teeth.
The flux does not rotate but shifts clockwise and counterclockwise with each
armature-current reversal. With rotor inertia and appropriate timing of the armature
current reversal, the reluctance rotor can rotate continuously at a speed controlled by
the armature current frequency. The armature winding requires an alternating current
reversing in polarity in synchronism with the rotor position. The cost of the power
electronic controller must be as low as possible for automotive applications.
12
Figure 2.6: Principle operation of FEFSM (a) θe=0° and (b) θe=180° flux moves
from stator to rotor (c) θe=0° and (d) θe=180° flux moves from rotor to stator
The disadvantage of FEFSM when compared to PMFSM is the design of this
machine is too complicated. The low performance also one of the disadvantages of
this machine when compare to HEFSM.
2.5 Hybrid Excitation Flux Switching Machine (HEFSM)
Hybrid Excitation Flux Switching machine (HEFSM) has both PM and FEC
in the stator. It can be referred as “hybrid stator- PM with field excitation machine” It
utilize primary excitation by PMs as well as DC FEC as a secondary sources.
HEFSM have advantages where both PM machine and DC FEC synchronous
machine is combine. This advantages overcome the problem exist in PMFSM where
13
the disadvantage of increase in copper loss and reducing the efficiency, reduced
power capability, and also possible irreversible demagnetization of the PMs. With all
the active parts that consist of PM, DC FEC and armature coil at the stator, HEFSM
has been popular among the researcher. HEFSM more suitable for high-speed drive
applications due to its robust rotor structure and also similar to the switch reluctance
machine (SRM) compared to IPMSM. Another advantage of this machine is FEC
that can be used to control flux with variable flus capabilities and also produce high
performance.
Various type of this machine with combinations of stator slots and rotor plots
can be referred to figure 2.7. The operating principle of the proposed HEFSM is
illustrated in figure 2.8. The red and blue line indicate the flux from PM and FEC. In
figure 2.8(a) and (b), both fluxes are combined and move together into the rotor since
the direction of both PM and FEC fluxes are in the same polarity, hence producing
more fluxes with a so called hybrid excitation flux. Furthermore in Fig. 2.8(c) and
(d), where the FEC is in reverse polarity, only flux of PM flows into the rotor while
the flux of FEC moves around the stator outer yoke which results in less flux
excitation. As one advantage of the DC FEC, the flux of PM can easily be controlled
with variable flux control capabilities as well as under field weakening and or field
strengthening excitation.
a) 6 Slot-8Pole HEFSM b)12Slot-10Pole HEFSM
Figure 2.7: Various stator slot and rotor pole of HEFSM
14
Figure 2.8: The operating principle of the proposed HEFSM (a) θe=0° - more
excitation (b) θe=180° - more excitation (c) θe=0° - less excitation (d) θe=180° - less
excitation.
For the design HEFSSM by using 12 Slot-10 Pole with 0.4kg permanent
magnet, the specifications and parameters design on the paper can be a reference to
this project [7]. The machine in this research is composed of 12 PMs and 12 FECs
distributed uniformly in the midst of each armature coil. The term, “flux switching”,
is created to describe machines in which the stator tooth flux switches its polarity by
following the motion of a salient pole rotor. In this 12Slot-10Pole machine, the PMs
and FECs produce six north poles interspersed between six south poles. The three-
phase armature coils are accommodated in the 12 slots for each 1/4 stator body
periodically. The presence of excitation coil makes these types of machines more
attractive in terms of modulating the PM flux.
The design restrictions and target specifications of the proposed machine for
HEV applications are listed in Table I. The table includes the available and estimated
specifications of the HEFSSM for same items with IPMSM for LEXUS RX400h as
in [9]. The electrical restrictions related with the inverter such as maximum 650V
DC bus voltage and maximum 240V inverter current are set. Assuming that only a
15
water cooling system is employed as the cooling system for the machine, the limit of
the current density is set to the maximum of 20Arms/mm2 for armature winding and
20A/mm2 for FEC. The outer diameter, the motor stack length, the shaft radius and
the air gap of the main part of the machine design being 264mm, 70mm, 30mm and
0.8mm respectively, are identical with those of IPMSM. Under these restrictions, the
weight of the PM as an important design target value is set to be less than 1.0kg [7].
Table 2.1: HEFSSM Design Restrictions And Specifications For Hybrid Electric
Vehicle Applications
The target maximum power is set to be more than 123kW and the motor
weight to be designed is less than 35kg, resulting in that the proposed machine
promises to achieve the maximum power density of 3.5kW/kg similar to that
estimated of IPMSM in LEXUS RX400h. Commercial FEA package, JMAG-Studio
ver.10.0, released by Japanese Research Institute (JRI) is used as 2D-FEA solver for
this design. The PM material used for this machine is NEOMAX 35AH whose
residual flux density and coercive force at 20C0 are 1.2T and 932kA/m, respectively
while the electrical steel 35H210 is used for rotor and stator body [7].
Basically, the design parameters are divided into four groups such as those
related to rotor core, FEC slot shape, armature coil slot shape and PM. The rotor
parameters are rotor radius (D1), rotor pole height (D2), and rotor pole width (D3).
The FEC slot shape parameters are PM height (D4), FEC pitch (D5) and stator outer
core thickness (D6). The armature coil slot shape parameters are armature coil height
(D7), and armature coil width (D8) respectively. The distance between air gap and
16
PM (D9) and distance between FEC slot and PM (D10) are parameters associated
with air gap at inner and outer PM. These parameters are varied to reduce PM
demagnetization.
Figure 2.9: Original design of 12S-10P HEFSSM
Figure 2.10: Improved design of 12Slot-10Pole HEFSSM with 1.0kg permanent
magnet
17
Figure 2.11: Design parameter defined as D1 to D10
Table 2.2: Initial And Final Design Parameters Of 12slot-10pole HEFSSM For HEV
Applications
18
Table 2.3: Performance Comparison of Finally Designed 12Slot -10Pole HEFSSM
For HEV Applications
19
CHAPTER 3
METHODOLOGY
3.1 Design Restrictions and Specifications
The original design of 12S-10P HEFSM is magnified so that the main
machine geometrical dimensions such as outer diameter, motor stack length and shaft
diameter are identical with IPMSM used in HEV. As well for 12S-14P HEFSM
follow the same geometrical dimensions for this project. The enlarged motor with
the initial dimension of main machine parts including air gap, stator outer and inner
diameter, rotor outer and inner diameter and shaft diameter show in figure 3.1, while
the motor stack length is set to 70mm similar with IPMSM.
Table 3.1 shows the design restrictions and specifications of the 12S-14P
HEFSM for HEV application. The table includes available and estimated
specifications of the 12S-14P HEFSM for same items with IPMSM for Lexus
RX400h [7]. The geometrical design dimensions of main machine part of the
proposed 12S-14P HEFSM are set in which the PM volume is approximately 1.0kg
and it is similar with the PM volume in IPMSM. Under these restrictions, the weight
of the PM as an important design target value is set to be less than 1.0kg. For the
input voltage and current, the electrical restrictions related with the inverter is set to
maximum 650V DC bus voltage and maximum 360 Arms current is set to inverter
current. For the current density, the maximum 30Arms/mm2 for armature coil and
30A/mm2 for FEC are set. The target of maximum torque is 210 Nm. The target
20
maximum operating speed is similar to the maximum operating speed in IPMSM of
20,000r/min, while the target maximum power is set to be more than 123kW. The
target motor weight to be designed is set to be less than 35kg. The proposed motor is
expected to achieve a maximum power density of more than 3.5kW/kg compared to
that estimated in IPMSM for Lexus RX400h. To design this machine, commercial
FEA package, JMAG-DESIGNER ver.13.0, released by JSOL Corporation is used as
2D-FEA solver for this design. The PM material used for this machine is NEOMAX
35AH whose residual flux density and coercive force at 20C0 are 1.2T and 932kA/m,
respectively, while the electrical steel 35H210 is used for rotor and stator body.
Figure 3.1: Main machine dimension of the proposed HEFSM for HEV applications
Dshaft= 30mm
Dro= 84.2mm
Armature coil
Shaft
Field excitation coil
Dsi= 85mm
Dso= 264mm
ag=0.8mm
Permanent Magnet
21
Items Unit IPMSM HEFSM
Geometrical
dimension and
volume
Stator outer diameter mm 264 264
Motor stack length mm 70 70
Shaft radius mm 30 30
Air gap length mm 0.8 0.8
PM weight kg 1.1 1.0
Input voltage and
current
Max DC-bus voltage
inverter V 650 650
Max. inverter current Arms Conf. 360
Maximum Ja Arms/mm2 Conf. 30
Maximum Je A/mm2 NA 30
Output
performances
Maximum torque Nm 333 >210
Reduction gear ratio - 2.478 4
Max. axle torque via
GR Nm 825 >840
Maximum speed r/min 12,400 20,000
Maximum power kW 123 >123
Machine weight kg 35 <35
Power density kW/kg 3.5 >3.5
Ja = armature current density, Je = FEC current density, GR = gear ratio
Table 3.1: Design restrictions and specifications of the proposed 12S-14P HEFSM
Figure 3.2 shows the design parameter defined as D1 to D10. Table 3.2
shows the initial and final design parameters of 12 Slot-14Pole HEFSM. Figure 3.3
shows general flow diagram of deterministic design approach.
22
Parameter Details Initial
1.0PM volume (kg) 1.0
D1 Rotor radius (mm) 84.2
D2 Rotor pole height (mm) 21.2
D3 Rotor pole width (mm) 10
D4 PM height (mm) 20.1
D5 FEC slot pitch (mm) 19.0
D6 Stator outer core thickness (mm) 6.0
D7 Armature coil width (mm) 5.5
D8 Armature coil height (mm) 27.9
D9 Distance between air gap and PM (mm) 0.6
D10 Distance between FEC and PM (mm) 0.3
Na No. of turns of armature coil 6
ATe FEC ampere turn (AT) 2529.3
Sa Armature coil slot area (mm2) 153.53
SE FEC slot area (mm2) 210.8
T Torque (Nm) 221.17
P Power (kW) 122.7
pf Power factor 0.655
D PM Demagnetization (%) 0.0
FEC = Field excitation coil, PM = Permanent magnet
Table 3.2: Initial design parameters of 12S-14P HEFSM
23
Figure 3.2: Design parameter defined as D1 to D10
Figure 3.3: General flow diagram of deterministic design approach
Yes
Start
Change Rotor Parameters
D1,D2,D3
Change Field Excitation
Parameters D4,D5,D6
Change Armature Slot
Parameters D7,D8
P=123kW, T=333Nm
D=0%
Reduce PM
volume
End
No
Change Demagnetization
Parameters D9,D10
24
3.2 Flowchart of Project
Figure 3.4: Flowchart of project
START
Project background
Research & Problem
Statement
Design of initial design 12S-14P
HEFSM using JMAG designer
software
Simulation and analysis
P=123kW T=333Nm D=0%?
Final Report &
Presentation
Yes
Reduce Permanent Magnet Volume
END
No
71
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