The expressions of the material derivative of differential forms in the language of vector analysis are introduced. These formulae allow us to describe naturally the electromechanical coupling, and the coupling term appears to be a volume integral. A general approach to compute forces is then proposed, which takes that fact into consideration. The method is applicable in 2D and 3D with dual formulations. Numerical evidences of its efficiency are given.

The eggshell approach for the computation of electromagnetic forces in 2D and 3D

More efficient cooling systems are an enabler for the increase in power density in an electric traction motor. Contemplating to existing reviews, this article presents a comprehensive collection of heat transfer mechanisms for the different heat removal techniques used in electric traction motors. In this article, an overview of various cooling concepts in existing and future traction motors is presented, and the cooling approaches are compared. The following literature review compiles geometry-based calculation formulas of the different mechanisms of cooling heat transfer applied in motor technology. Furthermore, general heat transfer phenomena appearing in electric traction motors are reviewed and compiled for easy access. Various specifically relevant aspects, including rotor shaft cooling, different spray cooling concepts, different air convection phenomena, bearing heat transfer, and the stator-housing contact, are examined in more detail. For validation of the review result, based on a well-known motor design, thermal analysis and comparison of the different cooling methods are carried out. Modeling is done with a lumped parameter thermal network (LPTN). This article concludes by demonstrating the advantages and disadvantages of the different cooling concepts based on the collection of modeling data.

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Traction Motor Cooling Systems: A Literature Review and Comparative Study

A critical review on thermal management technologies for motors in electric cars

This paper gives a comprehensive review of advanced cooling schemes and their applications to the permanent magnet synchronous motors (PMSMs), as well as investigating the electrical motor’s topologies its thermal design issues, materials and performances. Particularly, the electromagnetic and electric performances, machine sizing, together with the structural design, are given. In addition, the work addresses the motor’s material design and properties along with its insulation performance, which is the main goal of optimization. Mainly, thermal mapping with analysis is provided according to the different cooling methods, including air-cooling, water-cooling, oil-cooling, heat-pipe-cooling, potting silicon gelatin cooling, and as well as cooling strategies for tubes and microchannels. The most common special features and demands of the PMSMs are described in the appearance of the motor’s failures caused by uncontrolled temperature rise. In addition, heat sources and energy losses, including copper loss, core loss versus motor speed, and output power, are analyzed. The review of the proposed cooling methods that will achieve the required heat transfer of the PMSM is presented with numerical simulations and measurements data. A review of numerical methods and results, including the finite element methods (FEM), such as the Ansys CFD software, to obtain a high-accuracy thermal mapping model of the PMSM system is given. The revived methods and design requirements due to PMSM temperature profile and cooling flow at different rotor speeds and torque loads are investigated. Finally, the motor design recommendations, including the newly developed cooling solutions, which enable it to effectively redistribute the temperature and heat transfer, increasing the efficiency of the PMSM machine, are laid out.

Thermal Mapping of a High-Speed Electric Motor Used for Traction Applications and Analysis of Various Cooling Methods—A Review

Thermal effects and manufacturing processes of different potting strategies are studied in this paper. In the first small prototype, winding is impregnated traditionally with a standard epoxy-based material and then potted using a thermally conductive epoxy. In the motor with global potting, a single material and process is used to enhance heat transfer from the copper conductors in the winding to the housing where the cooling ducts are located. The potted motors are then compared to a reference motor without potting and impregnated using standard resins. Steady-state and transient thermal measurements are made, and a comparative investigation is performed on the built prototypes. Moreover, influence of traction motor design on thermal effects of potting is studied and presented in this paper. Using the results achieved on the tested prototypes, end winding potting is applied to a real-size traction motor designed and built for electric off-road vehicles and thermal effects are investigated in a test setup where the potted and unpotted motor are placed back-to-back running in an identical operating point and under the same cooling conditions. Additionally, measurements on specific duty cycles are run with the aim of investigating the potting thermal performance in operating condition.

Thermal and Manufacturing Aspects of Traction Motors Potting: A Deep Experimental Evaluation

At low vehicle speed typical for urban areas the thermal limits of the electrical machine are mostly not reached due to the thermal time constants being much higher than the short time spans of high power demand However in a highway scenario a higher power is required continuously Due to rotor iron losses caused by the high frequency of the modern traction drive and the thermally insulating air gap at high speeds the rotor is the crucial element in terms of temperature In this paper the effect of an interior rotor air cooling to improve the thermal utilization is studied

Thermal Analysis of an Electrical Traction Motor with an Air Cooled Rotor

In dieser Arbeit wird am Beispiel eines Antriebsstrangs eines Serien-Elektrofahrzeugs eine Methode vorgestellt, welche das elektrotechnische mit dem strukturdynamischen Teilsystem ruckwirkungsbehaftet recheneffizient verbindet. Das transiente, nichtlineare Systemmodell berucksichtigt auf elektrotechnischer Seite Regelung, Leistungselektronik und das Verhalten der elektrischen Maschine unter dem Einfluss von Fertigungsabweichungen und strukturdynamischen Ruckwirkungen wie dynamischer Exzentrizitat, Torsion und Biegung des Rotors. Auf strukturdynamischer Seite ist der vollstandige Antriebsstrang inklusive. Wellensystem, Getriebe und Gehause in einer elastischen Mehrkorpersimulation zur Berechnung transienter Vorgange im Zeitbereich abgebildet. Die Methode erlaubt die Berechnung des nichtlinearen, akustischen Systemverhaltens und wird anhand von Prufstandsmessungen validiert. Die Moglichkeiten, durch Variantenrechnungen die Sensitivitaten des NVH-Verhaltens zu untersuchen oder Komponenten im Auslegungsprozess auf Systemebene zu optimieren, werden aufgezeigt.

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Die Kopplung elektrotechnischer und strukturdynamischer Domänen zu einem NVH-Systemmodell eines elektrischen Antriebsstrangs

Mit elektrischem Antrieb und modellbasierter Systemanalyse nahezu lautlos in die Zukunft

The accurate computation of multi-coupled electric drive systems is a complex process. In order to consider a variety of physical effects, their interactions as well as the interactions of different components, multiple fields of science have to be addressed. Numerical simulations help to compute these complex systems and to design machines in the best possible way for its specific application. The numerical computation scheme proposed in this study consists of six main sectors: the rough machine design, the preparation of the finite element method including the characterisation and modelling of materials, the electromagnetic simulation, the mechanical simulation, the control and power electronics and the thermal design and simulation. In each of the main sectors, different effects affecting the machine and the system behaviour can be considered and calculated. Depending on the application, they can be added or removed modularly in order to adapt the simulation effort and the simulation accuracy to the application. A detailed insight into the computation methods and approaches in each of these main sectors and their coupling is given in this study.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-smt.2019.0413

Markus Jaeger

Papers

Thermal Analysis of an Electrical Traction Motor with an Air Cooled Rotor

Die Kopplung elektrotechnischer und strukturdynamischer Domänen zu einem NVH-Systemmodell eines elektrischen Antriebsstrangs

Mit elektrischem Antrieb und modellbasierter Systemanalyse nahezu lautlos in die Zukunft

Complete and accurate modular numerical computation scheme for multi-coupled electric drive systems

Comprehensive model for the assessment of the NVH-behavior of electric vehicles