Analysis of Permanent Magnet Synchronous Machine for Integrated Starter-Alternator-Booster Applications Florin Nicolae Jurca, Mircea Ruba, Claudia Martis Department of Electrical Machi
Trang 1Analysis of Permanent Magnet Synchronous Machine for Integrated Starter-Alternator-Booster Applications
Florin Nicolae Jurca, Mircea Ruba, Claudia Martis Department of Electrical Machines and Drives Technical University of Cluj-Napoca
Romania florin.jurca@emd.utcluj.ro, mircea.ruba@emd.utcluj.ro, claudia.martis@emd.utcluj.ro
Abstract—In the last decade due to their high efficiency and
reliability, permanent magnet synchronous machine are widely
used in automotive applications There are two main reasons for
this trend: the reduction of the fuel consumption and the increase
of the travel comfort In this study we consider the approaches of
electromagnetic design of a special topology of permanent
synchronous machine (radial flux machine with outer rotor)
suited for automotive applications The study design requires
some analytical analysis, followed by a numerical one in order to
attain the performances of the proposed machine in all three
cases (starter-alternator-booster) A thermal analysis is required
in order to determine the thermal requirements for the
automotive applications
Keywords— permanent magnet motor; electromechanical system;
hybrid vehicule
I INTRODUCTION
Current research efforts related to electric cars have
problems mainly related to the accumulation of electricity In
this context (low autonomy, lack of fast charging stations) the
use of this type of machine is limited to urban trails Initially
considered as a transition between conventional vehicles and
the electric ones, the hybrid vehicles remain an alternative that
is gaining more ground by combining the advantages of both
types of vehicles Of the two types of series and parallel
hybrid vehicles, alternative series provides a simpler
connection between the two engines and transmission
powertrain Passing to the present path of development of
hybrid vehicles involves increasing the role in the operation of
the electrical machines by increase its power and
"responsibility" (starter-alternator-booster) The first steps
were be made by using a single electric machine as a
generator (alternator) and motor (starter) for starting the
internal combustion engine, but for a hybrid car a second
electrical machine is used for the electric propulsion The
simplification of this structure involves the use of a single
electric machine incorporating three operating modes:
starter-alternator-booster (ISAB) In this case ISAB will initially be
able to start internal combustion engine, then when turned on
will switch to a generator and will supply the electricity
consumers and the electricity storage system Due to the
control strategies used, electrical machine is capable to move
quickly from generator to motor (booster) and back to help
the internal combustion engine for a short period of time (maximum 2 minutes), in situations where additional mechanical energy is necessary (overruns, ramps etc) [1, 2] The ISAB can be connected to a gasoline or diesel engine either directly through crankshaft or indirectly through belt drive, and they are accordingly called the belt-driven starter alternator (BAS) and normal ISAB, respectively The permanent synchronous machine with outer rotor is an innovative solution of direct connection to the internal combustion engine in both cases in the context of minimal mechanical losses Comparative whit other types of electrical machines, the permanent magnet (PM) synchronous machines have some important advantages like high power density, high efficiency and the possibility to work in high overload [3] The present paper approaches the design and analysis of a special topology of interior permanent magnet synchronous machine (IPMSM) suited for automotive application, shown in Fig.1 This machine is characterized by anisotropic rotor, that
is benefit when flux-weakening operations are required The motor torque is due to two components: one is due to the PM flux and the other to the rotor saliency In addition, the anisotropic rotor is advantageous in order to detect the rotor position without using a position sensor [3]
Fig.1 Structure of the ISAB: 42-slot 14 pole IPM machine
Trang 22015 International Conference on Electrical Drives and Power Electronics (EDPE) The High Tatras, 21-23 Sept 2015
A preliminary design procedure will be performed using
SPEED program and the results will be implemented in a FEM
based software in order to analyze the performances of the
machine: magnetic field density, induced emf, torque and
current After that a thermal analysis is required because the
thermal behavior can drastically influence the machine's
performances Thus a special attention should be paid on the
heat transfer within the active and non-active parts of the
machine
II PRELIMINARY DESIGN
The initial phase of the design was conducted using SPEED
software The SPEED software allows very fast performance
estimation of the electrical machine The software is mainly
based on analytical computations The motor structures were
refined using ranging analysis that helps to determine the
influence of geometrical and electrical parameters on the
motor performance
In order to improve the electrical machines performances,
several winding topologies will be analyzed The output
performances of the studied motor are: P – 7 (kW); rated
voltage Un – 72 (V); rated speed n n – 500 rpm; pole pair
number p – 14 The rotor has three flux barriers per pole The
dimensions of the PMs are equal to 2 x 10 mm, 2.5 x 16 mm,
3 x 18 mm The obtained main dimensions and the results for
the operation at rated point are shown in Table1
TABLE I GEOMETRIC AND RESULTS PARAMETERS FOR THE
DESIGED MACHINE Stator outer diameter [m] 0.210
Rotor outer diameter [m] 0.150
PM residual flux density [T] 1.42
III MAGNETIC FIELD ANALYSIS
The finite element method (FEM) is a powerful tool for the
design of the electrical machines and others electromagnetic
devices FEM is a simple, robust and efficient widely used
method of obtaining a numerical approximate solution for a
given mathematical model of the machine This analysis has
been carried out using Flux2D software
The magnetic flux density map in the cross-section of the
machine is presented in Fig.2 and the flux lines distribution in
Fig 3
For no-load condition, the air-gap magnetic flux density distribution is depicted in Fig 4, giving an average value of 0.72 T
Fig 2 Map of flux density
Fig.3 Flux lines distribution
Fig 4 Air-gap magnetic flux density
-1.5 -1 -0.5 0 0.5 1 1.5
rotor angle [o]
Trang 3The regime operation in load condition will be simulated in
order to obtain de torque value at rated speed
Fig 5 Torque variation in time
In order to evaluate the efficiency of the machine in starter
an alternator mode the iron losses was computed for obtained
the efficiency map of ISAB The machine efficiency for over
the entire torque (current)/speed of starter and alternator
regime, considering the copper losses (80oC) can be seen in
Fig.6 and Fig.7 From this efficiencies map, the machine
losses can be extracted and used as input data for a thermal
simulation of the machine
Fig.6 Starter efficiency map
Fig.7 Alternator efficiency map
Because this structure is proposes to automotive
application, we are trying to find a solution to reduce the
torque ripples Theoretically, skewing the stator and rotor core
might produce very smooth torque wave For that, we have
analyzed the proposed machine with the Flux/Skewed
computation module In this case it is easier to make rotor in
Skewed technology
Fig.8 Skewing the IPMSM: flux density repartition
The geometry of the IPMSM 42/14 was drawn in 2D and after that we have considered an angle of incline of 1 slot (360/42) The effect on rotor sheets incline, as well as the core flux density repartition, is shows in Fig 8 Now, one can verify the torque repartition for the skewed machine, Fig.9 The torque varies between 153 and 158, meaning that the torque ripple corresponds to 3.2% This is an important decrease of torque ripple content This gain can be decisive while preparing the control of the IPMSM
Fig 9 IPMSM, torque ripples: with or without skewing effect
For the proposed machine Flux program (Skew module) was used in order to observe the behavior of the machine in all operating regimes (starter-alternator-booster) Thus, we accomplished a simulation scenario in which the proposed machine is analyzed in the three considered operating regimes
In order to do this the circuit presented in Fig 10 was implemented
Fig 10 The circuit model of ISAB regime
100
110
120
130
140
150
160
170
180
190
Time [s]
7
.35
24
72.9
429
74.5
3
.53
76.1
38
.12
77
.7
43
79.3 48
8 89
57
57
.48
62
762
.0
67
85.6
667
.66
87.2
571
87.2
571
8 25
88.8
476
88.8
476
8 84
90.4381 90.4381
90.4
381
90.4
381
9 43
92.0286
86
9 02
93.619
9
93.619
95.2095
Speed [rpm]
40
60
80
100
120
140
160
84.8714
85.5667
85.5667
86.2619
86.9571
87.65 24
87.6524
87.6524
88.34
88.3 4 76
88.3476
88.3476
8
4
.04
8 04
89.0429
89.0429
.73
.73
8 73
89.7381
90.4333
90.4333
9 43
2
.12
.12
91.8238
.82
9
1
.51
92
.519
.21
93.2143
.90 93.2143
Speed [rpn]
10
15
20
25
30
35
0 20 40 60 80 100 120 140 160 180
time [s]
IPMSM IPMSM-skewed
Trang 42015 International Conference on Electrical Drives and Power Electronics (EDPE) The High Tatras, 21-23 Sept 2015 The behavior of the machine in all three regimes is
presented (starter-alternator-booster) in Fig 11 (torque
profile), Fig 12, 13 (phase voltage and current on the
machine), Fig 14 (dc voltage and current obtained on the
load)
Fig 11 ISAB torque profile
Fig.12 Three phase voltage obtained in ISAB regime
Fig.13 Three phase current obtained in ISAB regime
Fig.14 DC voltage and current obtained in alternator regime
IV THERMAL ANALYSIS
In automotive applications with combustion engine, the
thermal behavior can drastically influence the machine's
performances Thus a special attention should be paid on the
heat transfer within the active and non-active parts of the
machine The heat sources on the machine are: the cooper
loss, the iron loss and the mechanical loss The thermal analysis for the proposed machines was carried out using dedicated software Motor-CAD After implementing the geometry, the winding, the materials, iron and joule losses, the cooling condition and torque profile depending on time are defined In our case we consider the force cooling using water jacket
Usually the starter procedure lasts about 1 second, so in Motor-CAD we have set it to 10 second in order to obtain relevant results about the obtained temperature in the machine
in starter mode For starter mode we have considered 15 second in condition of variable load, and for booster we set 10 second The analysis was made for 40 duty cycles Highest temperatures were obtained the winding and stator back iron (91 C0),while in the permanent magnet the temperature is around 92 C0
a) radial view
b) axial view
Fig.15 IPMS temperature values
-40
-20
0
20
40
60
80
100
120
140
160
time [s]
ALTERNATOR
STARTER
BOOSTER
-60
-40
-20
0
20
40
60
time [s]
-60
-40
-20
0
20
40
60
time [s]
-10
0
10
20
30
40
50
60
70
80
90
100
time [s]
DC Voltage
DC Current
Trang 5Fig 16 Duty cycle configuration
Fig 17 Thermal analysis of the proposed machine, with Motor-CAD:
temperatures variation on duty cycle's
V CONCLUSIONS
In this paper a structure of permanent magnet synchronous
machine with outer rotor, suitable for automotive application
(integrated starter-alternator-booster) is presented The
preliminary design model of the machine was developed
followed by a simulation with finite element method in Flux
2D for ISAB regime The results obtained here provide
valuable information on the machine's behavior in all three
operating mode The thermal analysis for the proposed
machines was carried out in order to evaluate the thermal
stress of the ISAB
This work was supported by the:
1.Research-Development-Innovation Internal Projects of the
Technical University of Cluj-Napoca Strategic research topics for
young teams: DESIGN DESIGN, ANALYSIS AND CONTROL OF
PERMANENT MAGNET SYNCHRONOUS MACHINES AS
STARTER-ALTERNATOR-BOOSTER UNIT FOR HYBRID
ELECTRIC VEHICLES
2.Romanian Executive Agency for Higher Education, Research,
Development and Innovation Funding (UEFISCDI) under the
AUTOMOTIVE LOW-NOISE ELECTRICAL MACHINES AND
DRIVES OPTIMAL DESIGN AND DEVELOPMENT
(ALNEMAD) Joint Applied Research Project (PCCA) in the frame
of "Partnerships" projects (PN II – National Plan for Research,
Development and Innovation)
3 DEsign, Modellling and TESTing tools for Electrical Vehicles
(DEMOTEST), in the frame of FP7 IAPP Marie Curie Actions
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starter-alternator applications” Industry applications society annual
meeting (IAS), IEEE 386-393 (2004)
[2] M Barcaro, A Alberti, L.Faggion, M Sgarbossa, Dai Pr’e M, N
Binachi, S Bologni, “IPM machine drive design and tests for an
integrated starter-alternator application” Industry applications society
annual meeting (IAS), IEEE 1-8 (2008)
[3] M Barcaro, A Alberti, L.Faggion, M Sgarbossa, Dai Pr’e M, N
Binachi, “Expereimental tests on a 12-slot 8-pole integrated starter-alternator” Proceedings of the 2008 International Conference on
Electrical Machines 1-6
[4] Mirahki, H ; Moallem, M " Design improvement of Interior Permanent Magnet synchronous machine for Integrated Starter Alternator application ", Electric Machines & Drives Conference (IEMDC), 2013 IEEE International DOI: 10.1109/IEMDC.2013.6556279 Publication Year: 2013 , Page(s): 382 - 385 Cited by: Papers (1) IEEE Conference Publications
[5] M.Ruba, D.Fodorean : Analysis of Fault-Tolerant Multiphase Power Converter for a Nine-Phase Permanent Magnet, IEEE Trans On Industrial Applications, Vol 48, no 6, pp 2092-2101, ISSN:
0093-9994, 2012
[6] F.Jurca, R.P Hangiu, C MarĠiú -"Design and performances analysis of
an Integrated Starter-Alternator for Hybrid Electric Vehicles" Conference on Interdisciplinary Research in Engineering Steps towards Breakthrough Innovation for Sustainable Development, INTERIN, Cluj-Napoca 2013, pp 453-460, ISBN: 978-3-03785-785-4
JURCA Nicolae Florin: graduated
Electrical Engineering and received the PhD degree in Electrical Engineering from Technical University of Cluj-Napoca, Romania, in 2004 and 2009 respectively Since 2007 he is member
of the teaching staff of the Faculty of Electrical Engineering at Technical University of Cluj-Napoca He is currently Lecturer with the Department of Electrical Machines and Drives of the same university and him research is focused on electrical machines and drives design, modeling, analysis and testing for automotive, renewable energy-based and industrial applications
MARTIS Claudia: graduated Electrical
Engineering and received the PhD degree
in Electrical Engineering from Technical University of Cluj-Napoca, Romania, in
1990 and 2001 respectively Since 1996 she is member of the teaching staff of the Faculty of Electrical Engineering at Technical University of Cluj-Napoca She
is currently Professor with the Department of Electrical Machines and Drives of the same university and her research
is focused on electrical machines and drives design, modeling, analysis and testing for automotive, renewable energy-based
and industrial applications
Mircea Ruba He received B.Sc., M.Sc
and Ph.D degree from Technical University of Cluj in electrical engineering in 2007, 2008, respectively in
2010 He is a researcher working in the field of switched reluctance machines The results of his researches were published in more than 30 papers in journals and international conference proceedings