Electric Machine Comparison for Mild Hybrid Light Vehicles with Respect to Performance and ...

97 Pages·2017·17.89 MB·English

Electric Machine Comparison
for Mild Hybrid Light Vehicles
with Respect to Performance
and Thermal Capability
Master’s Thesis in Electrical Power Engineering
SEBASTIAN LARQVIST
HANNES ÖSTERGREN
Department of Energy and Environment
CHALMERS UNIVERSITY OF TECHNOLOGY
Gothenburg, Sweden 2017
Master’s thesis 2017
Electric Machine Comparison
for Mild Hybrid Light Vehicles
with Respect to Performance
and Thermal Capability
SEBASTIAN LARQVIST AND HANNES ÖSTERGREN
Department of Energy and Environment
Division of Electric Power Engineering
Chalmers University of Technology
Gothenburg, Sweden 2017
Electric Machine Comparison for Mild Hybrid Light Vehicles
with Respect to Performance and Thermal Capability
Sebastian Larqvist & Hannes Östergren
© SEBASTIAN LARQVIST & HANNES ÖSTERGREN, 2017.
Supervisors:
Stefan Skoog, Chalmers University of Technology
Patrik Stridh, Volvo Car Corporation
Alexander Robertsson, Volvo Car Corporation
Examiner:
Torbjörn Thiringer, Chalmers University of Technology
Master’s Thesis 2017
Department of Energy and Environment
Division of Electric Power Engineering
Chalmers University of Technology
SE-412 96 Gothenburg
Telephone [phone]
Cover: Field plots over magnetic flux density in four studied machine topologies:
PMSM, SynRM, PMSynRM and IM.
Gothenburg, Sweden 2017
iv
Electric Machine Comparison for Mild Hybrid Light Vehicles
with Respect to Performance and Thermal Capability
SEBASTIAN LARQVIST
HANNES ÖSTERGREN
Department of Energy and Environment
Chalmers University of Technology
Abstract
In this thesis, various electric machine topologies have been modeled and optimized
according to constraints related to mild hybrid applications. With the assistance of
electromagnetic field calculation software using FEM simulations, the performance
characteristics as well as thermal capability have been analyzed. By utilizing full
vehicle simulations, the machines have been evaluated and the performance quan-
tified when they are implemented in a 48 V mild hybrid system. Moreover, power
losses for whole operating regions in various machine components have been speci-
fied, which are used as input data for the thermal models. From the thermal model,
the temperature distribution within the machines have been determined during con-
tinuous operation. In this work, four machine topologies were chosen to be studied:
PMSM, SynRM, PMSynRM and IM. A number of operating points relevant to mild
hybrid systems were selected to be used as basis for the performance comparison.
From the simulations, it was found that the 8-pole PMSM has the highest op-
erating efficiency of 96.9 %. The implemented ferrite magnets of the PMSynRM
improve the highest operating efficiency by 1 % and increase the maximum torque
by 7 Nm compared to the SynRM. The PMSM and the IM fulfill the cold crank
torque requirement, and all machines can be operated at 10 kW continuously without
exceeding the critical temperature limits. The SynRM has the most environmen-
tal friendly design in terms of material combination, emissions are 53 % less in
comparison the 4-pole PMSM.
To conclude, due to beneficial properties such as high power and torque density,
along with great performance in the specified operating points and solid thermal
characteristics, the PMSM topology is found to be an interesting option to be uti-
lized in mild hybrid traction applications. Furthermore, the ferrite magnets in the
PMSynRM makes likewise this machine topology an interesting alternative to be
applied in mild hybrids, due to the overall high operating performance in relation
to its low material cost and CO2 equivalent per produced machine.
Keywords: Mild Hybrid, Electric Vehicle, Electric Machine, PMSM, SynRM,
IM, FEM, Operating Efficiency, Thermal Capability.
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Acknowledgements
First of all, we would like thank our main supervisor Stefan Skoog for his vital
support, feedback, and for sharing his inspiring research in the field of mild hybrid
applications with us. We would also like to express our sincere gratitude towards
our examiner Professor Torbjörn Thiringer, for always dedicating his time and his
great encouragement during the thesis work. Furthermore, we would like to thank
our supervisors at Volvo Cars, Patrik Stridh and Alexander Robertsson, for their
commitment and for deepen our knowledge within the field of electrified vehicles.
In addition, we would like to address our appreciation to Andreas Andersson for
his helpful advice regarding FEM simulations, and to Emma Arfa Grunditz for her
guidance concerning thermal modeling of electric machines.
I, Sebastian, would like to thank my family and friends for the continuous love
and encouragement throughout the years, your support means everything.
I, Hannes, give my warmest thanks to my family, especially my dear fiancée
Emma for the endless love and support through all the years.
Sebastian Larqvist & Hannes Östergren, Gothenburg, June 2017
vii
List of Abbreviations
BEV Battery Electric Vehicle
BSG Belt Driven Starter-Generator
emf Electromotive Force
FEM Finite Element Method
HEV Hybrid Electric Vehicle
ICE Internal Combustion Engine
IM Induction Machine
IPMSM Interior Permanent Magnet Synchronous Machine
ISG Integrated Starter-Generator
MTPA Maximum Torque Per Ampere
PM Permanent Magnet
PMSynRM Permanent Magnet Assisted Synchronous Reluctance Machine
PMSM Permanent Magnet Synchronous Machine
SRM Switched Reluctance Machine
SynRM Synchronous Reluctance Machine
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