Upcoming seminars at IEA
Friday February 10, at 10:15 a.m., hall M:B (Mechanical Engineering building, Ole Römers väg 1, Lund)
Ph.D. Defense and Presentation:
"Modeling and Testing of Insulation Degradation due to Dynamic Thermal Loading of Electrical Machines"
Electrical machines in electrified vehicles are subjected to dynamic loadings
at different driving conditions, which results in dynamic temperatures. The aging
of the Electrical Insulation System (EIS) in electrical machines is caused by these
dynamic temperatures, namely high average temperatures and temperature cycles.
In addition, the degradation of EIS affects the lifetime of the electrical machine.
In this thesis, three cornerstones for lifetime estimation of electrical machines
in electrified vehicles are identified and studied, which are the usage, the degradation
mechanisms and the lifetime model. A combination of computational simulation
and lab testing is required to design a comprehensive model. Furthermore,
the indicators of EIS degradations and the diagnostic methods of stator segments
(or motorettes) and electrical machines with aged insulations are studied.
A system thermal model, including a drivetrain model of vehicles, a loss and
cooling model and a thermal model of electrical machines, is proposed to predict
the temperature distribution inside the electrical machine of an electrified vehicle.
The estimated dynamic temperature at the hotspot is one of the inputs to a lifetime
model of the electrical machines.
To identify the degradation mechanisms of the EIS under the dynamic temperatures,
both enameled wires and motorette specimens are tested with accelerated
degradation tests. It is found that the aging of the EIS of an electrical machine subjected
to the dynamic temperature is not only caused by oxidation of insulations
with high average temperature, but also caused by the fatigue of insulations due
to thermal-mechanical stress induced by the temperature or thermal cycles. A revised
lifetime model of electrical machines is proposed, which covers both aging
mechanisms mentioned above. Another input to the lifetime model, the thermalmechanical
stress is estimated by Finite Element Analysis (FEA) using Ansys
The condition monitoring approaches are simulated by both electrostatic FEA
model and analytical model and implemented during the accelerated degradation
testings. These approaches assess the State of Health of the EIS of motorette specimens
. Insulation capacitance shows more consistent trends during aging at different
stress levels compared to insulation resistance. Insulation capacitance reduction
of 4 to 6% and 11 to 12% are found between winding and winding and
between winding and ground, respectively. A diagnostic method is proposed for
measuring the high frequency current with a voltage pulse simply set by the drive
of an electrical machine. The migration of both amplitude and frequency of the
current detected are indications of aging of the insulation system of an electrical
machine due to the decrease of the insulation capacitance.
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Prof. Mats Alaküla (Lund University, Sweden)
Senior Lecturer Avo Reinap (Lund University, Sweden)
Prof. Elias Strangas (Michigan State University, USA)
Prof. Pascal Maussion (Université de Toulouse, France)
Prof. Sture Eriksson (Sture Eriksson R&D consultancy)
Assoc. Prof. Sonja Lundmark (Chalmers, Göteborg)
Dr. Rafal Wrobel (University of Bristol, UK)
Assoc. Prof. Ulf Jeppsson (Lund University, Sweden)
Seminars are held in the IEA lecture room, ground floor in southeastern corner of the M-building, unless stated otherwise.
Seminar Announcer:Finn Landegren.