Table Of ContentZhiguang Cheng
Norio Takahashi
Behzad Forghani Editors
Modeling and Application
of Electromagnetic
and Thermal Field in
Electrical Engineering
Modeling and Application of Electromagnetic
and Thermal Field in Electrical Engineering
Zhiguang Cheng Norio Takahashi
(cid:129) (cid:129)
Behzad Forghani
Editors
Modeling and Application
of Electromagnetic
and Thermal Field
in Electrical Engineering
123
Editors
Zhiguang Cheng NorioTakahashi (deceased)
Institute of Power Transmission Okayama,Japan
andTransformation Technology
Baobian Electric Co.,Ltd.
Baoding, Hebei,China
Behzad Forghani
Mentor Infolytica, aSiemens Business
Montreal,QC, Canada
ISBN978-981-15-0172-2 ISBN978-981-15-0173-9 (eBook)
https://doi.org/10.1007/978-981-15-0173-9
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Foreword
The distribution and use of electrical energy is fundamental to the functioning of
modern society. From the discovery of electromagnetic energy around 200 years
ago to the present, devices based on converting energy between electromagnetic,
mechanicalandthermalformshavebecomesoprevalentthattheyarehardlygiven
a second thought and yet every one of those devices from large industrial
machinery; through land, air and sea transportation to domestic devices ranging
from washing machines to stoves, has to be designed, manufactured and tested. In
addition,agenerationanddistributionsystemforelectricalenergywhichisreliable,
robustandefficient,hastobeconstructed.In2017,about26,000TWhofelectrical
energy wasgenerated, distributedandusedglobally.Tominimize thelosses inthe
transmission and distribution system and reduce the costs of the infrastructure,
electricalenergyisusually transmitted ata veryhigh voltage, while it isgenerated
andusedatsignificantlylowerlevels. Thisimpliestheneedfor devicescapableof
changing voltages, i.e. transformers. It is interesting to consider that every Wh of
electrical energy delivered through the distribution system and subsequently used
has passed through at least two and probably nearer to ten, transformers.
Fromtheverybeginningoftheelectromagneticera,theneedfordesigntoolshas
beenparamount.Buildingphysicalprototypesisprohibitivelyexpensivebothinthe
costofeachprototypeandinthetimetakentorealizeafinaldevice.Simpledesign
tools based more on experience than theory evolved relatively quickly in the
nineteenth century and the development of electromagnetic field theory provided
the explanation of the physics underlying the operation of such devices. In effect,
designers from the start have been using whatever tools and representations they
can to create a virtual model of the device to determine the probable performance
and explore the design space. With the advent of digital computers, the possibility
ofsolvingthefieldequationstosimulatetheactualperformanceofadevicemoved
fromaconcept toreality. Overthepasthalfcentury,boththecomputinghardware
and the numerical methods necessary for solving the partial differential equations
togetherwithadvanced representations ofmaterial properties,etc., havedeveloped
to a point where the simulations may now be considered accurate “digital twins”
ofthephysicaldeviceallowing,inmanycases,moredetailedexplorationsofdevice
v
vi Foreword
performance than is possible on the physical system. These twins not only enable
thetotalelapsedtimefromspecificationtofulldesigntobedecreaseddramatically
(along with a substantial reduction in costs) but also allow for manufacturing
questions to be answered during the construction process and for performance
monitoringduringtheoperationofthephysicaldevicetoidentifydevelopingfaults
before they become critical. This is a fundamental component of the concepts
involved in moving to an “Industry 4.0” based world.
However, there are many requirements placed on the digital twin. First, it must
representtheperformanceoftherealdevicetothelevelofaccuracyneededbythe
designer.This can varythrough thedesignprocess and, typically,follows thewell
known“V-cycle”,i.e.intheinitialphasesofadesign,asystemlevelrepresentation
ofthedeviceisneeded—sometimesreferredtoasaReducedOrderModel—which
incorporatesasmuchofthemulti-physicsoperationofthedeviceaspossiblewhile
allowing a fast exploration of the design space. This is sometimes referred to as
“Front-Loading”thedesignprocess.Asthedesignprogresses,thesimulationneeds
tobecomemoredetailedtoanswerquestionssuchasthedistributionoflocallosses
in the device, the temperature rise in various components due to the losses, the
forces on various components, etc. However, while it is tempting to just build
extremely large models involving millions or tens of millions of degrees of free-
dom, the time taken to generate the performance of the twin and to explore the
design space is critical. To be competitive, it is important that the overall design
time is reduced as much as possible.
Fromtheabovediscussion,thedigitaltwinofanelectromagneticdeviceshould
involve an appropriate numerical representation of the electromagnetic field. Since
the behaviour of the field is controlled by the magnetic, electric, thermal and
structuralperformanceofthematerialsusedtoconstructthedevice,itiscrucialthat
anysimulationsystemmodelsthepropertieseffectively.Inaddition,becauseallthe
areasofphysics—magnetics,thermal,structural—arelinkedthroughthematerials,
avalidsimulationmustincludeafullmulti-physicsrepresentationand,becausethe
losses impact the thermal performance, the most important is an effective
magnetic-thermal representation of the device. However, the behavior of the field
also impacts the construction. For example, reducing losses in ferromagnetic
components leads to a need to laminate the cores carrying the magnetic fluxes.
These laminations are usually sub-millimeter in thickness while the dimensions
oftheentiredevicemayoftenbemeasuredinmeters.Theissuesofscalecanleadto
hugenumericalsystemsifallthedetailsofthedevicearemodeledaccurately.This,
in turn, can lead to extremely long simulation times. However, by representing
some of the smaller components of the device with compact models, the problem
sizes can be reduced significantly with no real loss in accuracy but with a massive
gain in simulation speed allowing the digital twin to run on significantly smaller
hardware systems.
This book provides an overview of the state-of-the-art for many of the issues
describedearlier.Ithasbeencreatedbyauthorswhohavesignificantexperiencein
eachoftheareascriticaltoconstructingandverifyingthevalidityofadigitaltwin.
Theyarerecognizedinternationalauthoritiesineachoftheirareasandseveralhave
Foreword vii
been involved in organizations such as the International Compumag Society, the
IEEE and standards organizations. They have made fundamental contributions to
the representation and solution of electromagnetic field problems, the accurate
modeling of materials, the measurement of material properties under the actual
operating conditions experienced within a device, the construction of simulation
systems,thedevelopmentofverificationandvalidationmodelsforsoftwareandthe
development of optimization processes for an effective search of the design space.
The book has been edited by three internationally recognized experts in the field:
Dr. Zhiguang Cheng who has decades of experience in electromagnetic analysis,
thevalidationofmodelingandsimulationtools,themeasurementandpredictionof
material properties and, together with a large research and development team, has
been involved in developing some of the world’s largest transformers (with
Baobian Electric, China); Prof. Norio Takahashi (from Okayama University,
Japan),whoreceivedtheNikolaTeslaawardfromtheIEEEin2013forhisworkin
modeling and design of electrical machines and was one of the leading developers
of numerical formulations of electromagnetic field problems as well as having
considerable expertise in material modeling; and Mr. Behzad Forghani who has
been involved in the development of industrial software tools for electromagnetics
design since the early 1980’s (with Infolytica, Canada—now Mentor-Infolytica, A
SiemensBusiness)andhasbeenamemberoftheInternationalCompumagSociety
Board for more than two decades. The resulting text represents man-centuries of
experience in efficient modeling, numerical simulation and experimental verifica-
tion of the complex engineering problems encountered in real electromagnetic
devicesandexplainsandidentifiestheissuesthatarecrucialtoanyonedeveloping
or using digital twin representations of such systems.
Althoughthecontentshavebeencreatedwiththetransformerdesignerinmind,
much applies to almost any low frequency electromagnetic device. The initial
chaptersinthefirstpartdiscussthemostoftenusedapproachestakentodeveloping
anumericalrepresentationofthemagneticfield.Theissuesandadvantagesofeach
approach are discussed, and the reader is provided both with the theoretical
development and with computational experiments which demonstrate the effec-
tivenessoftheapproachesintermsoftheproblemsizesandtypicalsolutiontimes.
While the representations deal with the basic field equations, constructing an
effective system requires the introduction of knowledge and understanding to
minimize the problem sizes without sacrificing accuracy. Thus, the next sections
deal with issues which are of engineering importance, including optimization
processesforexploringthedesignspace.Thethemehereisverymuch“howcanwe
develop an effective design tool?”. This highlights the needs of the practicing
designer of both speed of simulation and accuracy of solution. However, the
importanceoflinkingthethermalandmagneticfieldcalculationsisstressedand,in
manydevices,itisthethermalimpactofthemagneticfieldthatcausessomeofthe
most severe design issues and leads to many of the engineering problems which
must be solved. The culmination of these discussions is demonstrated by the
simulation system, “SimcenterTM MAGNETTM”. This is an example of a com-
mercialtoolthatimplementsmanyoftheconceptsdiscussedpreviously.However,
viii Foreword
no tool can provide for every possibility that a designer wants so the ability to
develop customizations, or shells, shows how the power of the digital twin can be
leveraged for specific performance requirements. Finally, recognizing that the
transientperformanceofdevicesisbecomingevermoreimportant,anapproachfor
accelerating these computations is discussed.
Possibly the most interesting component of this book is the detailed review of
materialpropertiesandtheirmodeling.Materialpropertiesdominateinthesolution
offield problems and an understanding of the issues involved, from the behaviour
under non-sinusoidal conditions, in the presence of dc bias and with rotational
fluxes, to the impact of temperature on the behavior is critical in developing an
effective and accurate simulation. An understanding of the properties and their
variancescanalsohelpanengineertounderstandwhatlevelsofaccuracyitmakes
sense to request from the system. This section of the book draws on expertise in
materialpropertyandmeasurementwhichissecondtononeintheworld.Thework
of Prof. Norio Takahashi (Okayama, Japan) and Prof. Johannes Sievert
(Braunshweig, Germany) is internationally recognized. In addition, the practical
information on making measurements, the effect of core structures on properties
and the design of experimental facilities, based on industrial experience, is extre-
mely valuable in understanding what can realistically be done. This work is very
timely—it deals with issues that are arising because of geomagnetically induced
currents (a problem that all transformers must now be designed to survive),
renewable energy systems, such as wind generation, that create huge time varying
effects and high voltage dc (HVDC) transmission systems. Iffor no other reason,
thisbookstandsoutinthewayitdiscussestheissueswithmaterialperformancein
a real device.
Notwithstanding the above, no digital twin is acceptable unless its performance
has been validated and verified. The authors of this book have been involved, for
about two decades, with the development of a series of variations of an interna-
tionally accepted test model for software performance validation. The model,
TEAM problem 21, includes many of the basic features found in a large power
transformer and the experimental version of the problem has been built, and its
performance modeled and measured, as co-research projects, jointly organized by
Zhiguang Cheng, Norio Takahashi and Behzad Forghani.
Whilemuchoftheinformationprovidedinthebookisofgeneralusetoanyone
workingonthedesignoflowfrequencyelectromagneticdevices,thelastpartdeals
specifically with issues encountered in large modern power transformers expected
tooperatewithinthenewgridarchitecturesthatarebeingproposed.Theexperience
and knowledge embedded here is likely to be immensely valuable to anyone
involved in transformer design to meet current operational requirements and
international standards.
Overall, this work is an extremely comprehensive review of issues encountered
in the design process for electromagnetic devices. It is a book which is targeted at
both the research engineer and the practicing designer who want to understand the
basisandcapabilitiesofmodernsimulationsystemsforelectromagnetics.Thebook
contains knowledge and information from experts in the field developed over
Foreword ix
decades ofboth research work and practical experience. With over 450references,
the book contains one of the most comprehensive lists available of the key publi-
cations in the area of electromagnetic-thermal modeling and provides the reader
with the opportunity to dig deeper into each of the areas covered.
David A. Lowther
Ph.D., A.K.C., C.Eng.(UK), P.Eng. (Ont), F.I.E.T., F.C.A.E., F.I.E.E.E.
Professor of Electrical Engineering
Department of Electrical and Computer Engineering
McGill University
Montreal, QC, Canada
e-mail: [email protected]
Preface
The co-research of theauthorsof this book, mainly involving 3-D electromagnetic
and thermal modeling and simulation, measurement and prediction of material
properties under standard and non-standard operating conditions, engineering-
oriented benchmarking, based on well-established and collaborative research plat-
forms, and transformer-related industrial applications, goes back to 30 years ago.
This co-publication is based on its former version published in 2009, but is con-
siderably extended, including the authors’ major recent co-research works.
Motivation
Theunprecedented high voltageandhigh capacity oftoday’selectrical equipment,
the economic pressures, as well as considerations, such as, the environmental
protection, and high reliability within the life cycle, increasingly impose new and
stringentrequirementsfortheefficientandaccurateanalysisanddesigntechniques,
inparticularwithregardstothesimulationofelectromagneticandthermalbehavior,
in large electromagnetic devices.
Modeling and prediction of the electromagnetic and thermal field behavior of
large electrical equipment, especially in the UHV transmission and transformation
engineering, lay the foundation for the in-depth study of topics, such as, vibration
andnoise,heatingandcoolingeffects,underactualoperatingconditions.Itinvolves
material property modeling, large-scale multi-physics, multi-scale numerical anal-
ysis under complex conditions, and validation based on benchmark models,
product-level models, and/or experiments with actual products.
This book aims to report the research works related to the above key projects,
includingmany valuable measurement andsimulation results, to motivateresearch
teams to promote and participatein cooperation and exchangesin these fields, and
to stimulate the exploration and discussion on future challenging topics.
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