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Number of results: 25
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Abstract

In industrialized countries cardiovascular diseases are the major cause of death. The last clinical therapy option for some patients, suffering from terminal heart diseases, is donor heart transplantation. As the available number of donor organs is decreasing, many patients die while waiting for a transplant. For this reason Ventricular Assist Devices (VADs), which can mechanically support the human heart to achieve a sufficient perfusion of the body, are under development. For an implantable VAD, design constraints have to be deduced from the physiological conditions in the human body. In case of a VAD drive, these constraints are for example dimensions, electric losses, which might result in an overheating of blood, and a long durability. Therefore a hybrid permanent magnet hydrodynamic bearing is designed in this paper, which works passively and contactless. Based on Finite Element simulations of magnetic fields, various permanent magnet topologies are studied in terms of axial forces and stiffness.

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Authors and Affiliations

André Pohlmann
Kay Hameyer
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Abstract

This paper presents a methodology for the calculation of the flux distribution in power transformer cores considering nonlinear material, with reduced computational effort. The calculation is based on a weak coupled multi-harmonic approach. The methodology can be applied to 2D and 3D Finite Element models. The decrease of the computational effort for the proposed approach is >90% compared to a time-stepping method at comparable accuracy. Furthermore, the approach offers a possibility for parallelisation to reduce the overall simulation time. The speed up of the parallelised simulations is nearly linear. The methodology is applied to a single-phase and a three-phase power transformer. Exemplary, the flux distribution for a capacitive load case is determined and the differences in the flux distribution obtained by a 2D and 3D FE model are pointed out. Deviations are significant, due to the fact, that the 2D FE model underestimates the stray fluxes. It is shown, that a 3D FE model of the transformer is required, if the nonlinearity of the core material has to be taken into account.

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Authors and Affiliations

Björn Riemer
Kay Hameyer
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Abstract

This paper describes the application of the skull melting method for an artificial generation of particulate material of inorganic compounds like CsOH, NaOH, SnO2 and UO2. The skull melting process is analyzed analytically. Thereby the electromagnetic field is calculated by a one dimensional time harmonic model. Thermal losses are estimated by simple analytical formulas. Finally an electromagnetic thermal field coupling is performed to calculate the temperature distribution inside the crucible, considering transient thermal effects. The skull melting process is simulated for the example of UO2. Under consideration of the given material properties it is shown that the skull melting method can be applied to fuse UO2.
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Authors and Affiliations

Björn Riemer
Enno Lange
Kay Hameyer
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Abstract

The purpose of this paper is to develop a dynamic thermal model of a permanent magnet excited synchronous motor (PMSM). The model estimates the temperature at specific points of the machine during operation. The model is implemented using thermal network theory, whose parameters are determined by means of analytical approaches. Usually thermal models are initialized and referenced to room temperature. However, this can lead to incorrect results, if the simulations are performed when the electrical machine operates under “warm” conditions. An approach is developed and discussed in this paper, which captures the model in critical states of the machine. The model gives feedback by online measured quantities to estimate the initial temperature. The paper provides an extended dynamic thermal model, which leads to a more accurate and more efficient thermal estimation.

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Authors and Affiliations

Christelle Piantsop Mbo’O
Kay Hameyer
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Abstract

A contactless energy transmission system is essential to supply onboard systems of electromagnetically levitated vehicles without physical contact to the guide rail. One of the possibilities to realise a contactless power supply (CPS) is by integrating the primary actuator into the guide rail of an electromagnetic guiding system (MGS). The secondary actuator is mounted on the elevator car. During the energy transmission, load dependent non-linear losses occur in the guide rail. The additional losses, which are caused by the leakage flux penetrating into the guide rail, cannot be modelled using the classical approach of iron losses in the equivalent circuit of a transformer, which is a constant parallel resistance to the mutual inductance. This paper introduces an approach for modelling the load dependent non-linear losses occurring in the guide rail using additional variable discrete circuit elements.

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Authors and Affiliations

Aryanti Kusuma Putri
Rüdiger Appunn
Kay Hameyer
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Abstract

In the electromagnetic field simulation of modern servo drives, the computation of higher time and space harmonics is essential to predict torque pulsations, radial forces, ripple torques and cogging torque. Field computation by conformal map ping (CM) techniques is a time-effective method to compute the radial and tangential field components. In the standard CM approach, computational results of cogging torque simulations as well as overload operations observe deviations to nonlinear finite element (FE) simulations due to the neglection of slot leakage and saturation effects. This paper presents an extension of the classical CM. Additional CM parameters are computed from single finite element computations so as to consider both effects listed above in the model over a wide operation range of the electrical drive. The proposed approach is applied to a surface permanent magnet synchronous machine (SM-PMSM), and compared to numerical results obtained by finite element analysis (FEA). An accuracy similar to that of FE simulations is obtained with however the low computation time that is characteristic for analytical models.

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Authors and Affiliations

Martin Hafner
David Franck
Kay Hameyer
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Abstract

The drive train of a small scale magnetically levitated train reveals the principles of a mechatronic system and offers challenges related to design, construction and control. Therefore, it is used at the Institute of electrical Machines (IEM) of the RWTH Aachen University as a demonstrator for engineering solutions. Instead of being a part of a static predefined student laboratory, the small scale magnetically levitated train is part of dynamic individual student projects. This approach provides the advantage that the students are directly involved in the engineering process and gain motivation out of their personal ideas becoming reality.
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Authors and Affiliations

Gregor Glehn
Rüdiger Appunn
Kay Hameyer
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Abstract

The free piston linear generator is a new range extender concept for the application in a full electric vehicle. The free piston engine driven linear generators can achieve high efficiency at part and full load which is suitable for the range extender application. This paper presents requirements for designing a linear generator deduced from a basic analysis of a free piston linear generator.

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Authors and Affiliations

Un-Jae Seo
Björn Riemer
Rüdiger Appunn
Kay Hameyer
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Abstract

This paper focuses on the design and control of an active suspension system, where a tubular linear motor is integrated into a spring damper system of a vehicle. The spring takes up the weight of the vehicle. Therefore the electric linear motor can be designed very compact as it has to provide forces to adjust the damping characteristic only. Design and construction of the active suspension system, a control strategy and validation measurements at a test bench are presented.
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Authors and Affiliations

Andreas Thul
Daniel Eggers
Björn Riemer
Kay Hameyer
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Abstract

In this paper a scaling approach for the solution of 2D FE models of electric machines is proposed. This allows a geometrical and stator and rotor resistance scaling as well as a rewinding of a squirrel cage induction machine enabling an efficient numerical optimization. The 2D FEM solutions of a reference machine are calculated by a model based hybrid numeric induction machine simulation approach. In contrast to already known scaling procedures for synchronous machines the FEM solutions of the induction machine are scaled in the stator-current-rotor-frequency-plane and then transformed to the torque- speed-map. This gives the possibility to use a new time scaling factor that is necessary to keep a constant field distribution. The scaling procedure is validated by the finite element method and used in a numerical optimization process for the sizing of an electric vehicle traction drive considering the gear ratio. The results show that the scaling procedure is very accurate, computational very efficient and suitable for the use in machine design optimization.

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Authors and Affiliations

Martin Nell
Jonas Lenz
Kay Hameyer
ORCID: ORCID
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Abstract

The purpose of this paper is to focus on the loss separation of non-grain-oriented electrical steels used for speed-variable rotating electrical machines. The impact of laser-cutting, used in prototype manufacturing and of flux density harmonics, occurring locally in the lamination, on the loss distribution is studied in detail. Iron losses occurring under operation can physically be separated in different loss components. In this paper, a frequency-based loss model with parameters identified for single-sheet tester specimens, cut in strips of different widths, is therefore used. Moreover, a time-domain approach considers loss distributions occurring from higher harmonics. Hysteresis losses having high sensitivity to cut edge effects are calculated by the well-known Jiles-Atherton model adapting the frequency-based loss parameters. The model is validated by free-curve measurements at a single-sheet tester. It has been shown that the studied elliptical hysteresis model becomes inaccurate particularly for specimens with small strip widths with similar dimensions as teeth of electrical machine laminations. The incorrect mapping of losses occurring from minor hysteresis loops due to higher harmonics is concluded. The results showconsequently that both, the impact of a cut edge effect and local distributions of flux density harmonics need to be considered in terms of accurate iron loss prediction of electrical machine design.

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Authors and Affiliations

Christoph Mülder
Silas Elfgen
Kay Hameyer
ORCID: ORCID
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Abstract

Variable speed and low voltage electrical drives are commonly operated by frequency converters. According to recent developments, there is a trend in the area of semi-conductors, that switching frequency and voltage slew rate will increase significantly. The aim of these semiconductors is to reduce the switching losses and to increase the switching frequency, which enables to reduce the size of passive components in the power- electric circuit. This results in less material effort and lower cost, for the power electronic component. However, electric motors operated by high slew rate inverters show problems in the winding insulation, which have to be analyzed. Such problems are well known for high voltage machines. Due to the increasing slew rate, this problematic occurs in low voltage machines nowadays as well. Here, the influence of fast switching semiconductors on the winding insulation system is studied, using accelerated ageing tests with fast switching high-voltage generators.

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Authors and Affiliations

Florian Pauli
Andreas Ruf
Kay Hameyer
ORCID: ORCID
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Abstract

Total Artificial Hearts (TAHs) are required for the therapy of terminal heart diseases as heart transplants are only a limited option due to the available number of donor hearts. For implantation TAHs have to meet constraints regarding its dimensions, weight, perfusions and electrical losses. An innovative linear driven TAH is presented, which meets all constraints except weight. Therefore the geometry of the linear drive is optimised to reduce its weights while simultaneously limiting the electrical losses as much as possible. In order to calculate the losses, this paper introduced a combined calculation chain consisting of FEM simulations and analytical equations. Based on this chain the linear drive is optmised by the method of parameter variations. The results yield a hierachic order of parameters which are most suitable for the weight reduction of the drive for low losses. By this the weight of the linear drive is reduced by 25%. As the allowable loss limit is not exceeded yet, room for further weight reduction achieved by an optimisation of the axial geomtry parameters is given.
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Authors and Affiliations

André Pohlmann
Thomas Schmitz-Rode
Marc Lessmann
Thomas Finocchiaro
Andreas Fritschi
Ulrich Steinseifer
Kay Hameyer
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Abstract

Different buried permanent magnet arrangements in rotors are compared based on electrical machines found in literature regarding high-speed capability. An analytical approach is presented to analytically calculate mechanical stresses in the bilateral and central bridge of V arrangements in order to determine the achievable circumferential velocity of a rotor geometry. The mechanical model is coupled to an analytical model which can determine the flux density in the main air gap under consideration of flux leakage within the rotor. The multi-domain model enables the analytical design of high-speed rotors with buried permanent magnets in V-arrangement.
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Authors and Affiliations

Maximilian Lauerburg
1
ORCID: ORCID
Polkrit Toraktrakul
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen UniversitySchinkelstr. 4, D-52062 Aachen, Germany
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Abstract

This paper studies the influence of different cooling technologies on the power density of a traction machine for heavy-duty distribution transport. A prototype induction machine is built with a housing cooling jacket, potted end-windings, entire winding cooling, and shaft cooling. Electromagnetic finite element and thermal lumped-parameter models are parameterized and verified using test bench measurements. The influence of each thermal resistance along the heat paths is studied and discussed. The results are used for studying different cooling technologies. The results indicate an improvement of the continuous power density up to 108% using shaft cooling and up to 15.6% using entire winding cooling.
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Authors and Affiliations

Benedikt Groschup
1
ORCID: ORCID
Daniel Butterweck
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Schinkelstraße 4, 52062 Aachen, Germany
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Abstract

The accurate prediction of iron losses has become a prominent problem in electromagnetic machine design. The basis of all iron loss models is found in the spatial field-locus of the magnetic flux density (B) and magnetic field (H). In this paper the behavior of the measured BH-field-loci is considered in FEM simulation. For this purpose, a vector hysteresis model is parameterized based on the global measurements, which then can be used to reproduce the measurement system and obtain more detailed insights on the device and its local field distribution. The IEM has designed a rotary loss tester for electrical steel, which can apply arbitrary BH-field-loci occurring during electrical machine operation. Despite its simplicity, the proposed pragmatic analytical model for vector hysteresis provides very promising results.

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Authors and Affiliations

Fabian Müller
Gregor Bavendiek
Benedikt Schauerte
ORCID: ORCID
Kay Hameyer
ORCID: ORCID
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Abstract

Accurate demagnetization modelling is mandatory for a reliable design of rare-earth permanent magnet applications, such as e.g. synchronous machines. The magnetization of rare-earth permanent magnets requires high magnetizing fields. For technical reasons, it is not always possible to completely and homogeneously achieve the required field strength during a pulse magnetization, due to stray fields or eddy currents. Not sufficiently magnetized magnets lose remanence as well as coercivity and the demagnetization characteristic becomes strongly nonlinear. It is state of the art to treat demagnetization curves as linear. This paper presents an approach to model the nonlinear demagnetization in dependence on the magnetization field strength. Measurements of magnetization dependent demagnetization characteristics of rare-earth permanent magnets are compared to an analytical model description. The physical meaning of the model parameters and the influence on them by incomplete magnetization are discussed for different rare-earth permanent magnet materials. Basically, the analytic function is able to map the occurring magnetization dependent demagnetization behavior. However, if the magnetization is incomplete, the model parameters have a strong nonlinear behavior and can only be partially attributed to physical effects. As a benefit the model can represent nonlinear demagnetization using a few parameters only. The original analytical model is from literature but has been adapted for the incomplete magnetization. The discussed effect is not sufficiently accurate modelled in literature. The sparse data in literature has been supplemented with additional pulsed-field magnetometer measurements.

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Authors and Affiliations

Gregor Bavendiek
Fabian Müller
Jamshid Sabirov
Kay Hameyer
ORCID: ORCID
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Abstract

To reduce the losses of the power electronic inverter, the voltage slew rate (d u/d t) of the electric motors supplying voltage is increasing. As steep voltage slopes excite high frequencies in the megahertz range, transient phenomena in the winding of the electrical machine occur. To design the insulation system, the maximum electric potential difference between the conducting elements must be predicted. General design rules can lead to a significant overengineering of the interturn insulation, particularly when considering smaller stators with a known wire distribution. Therefore, two different winding topologies are studied comparing the voltage distribution in a round-wire winding and a winding with preformed coils.
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Authors and Affiliations

Florian Pauli
1
Niklas Driendl
1
Sebastian Mönninghoff
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Germany
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Abstract

Production deviations have a remarkable effect on the radiated sound of electrical machines, introducing additional signal components besides the fundamental field waves which significantly change and enrich the subjectively perceived sound characteristic. In literature these harmonics are mainly traced back to dynamic eccentricity, which modulates the fundamental fieldwaves. In this paper a thorough mechanic and electromagnetic analysis of a modern, well-constructed traction drive (permanent magnet synchronous machine) is performed to showthat for this typical rotor configuration dynamic eccentricity is negligible. Instead, deviations in the rotor magnetization are shown to be the dominant cause for vibration harmonics.
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Bibliography

[1] Nahlaoui M.A., Steins H., Kulig S., Exnowski S., Comparison of numerically determined noise of a 290 kW induction motor using FEM and measured acoustic radiation, Archives of Electrical Engineering, vol. 62, pp. 195–207 (2013), DOI: 10.2478/aee-2013-0015.
[2] Gieras J.F., Wang C., Cho Lai J., Noise of polyphase electric motors, CRC Press Taylor and Francis Group (2006).
[3] Hu Y., Wei H., Chen H., Sun W., Zhao S., Li L., Vibration Study of Permanent Magnet Synchronous Motor Base on Static Eccentricity Model, 22nd International Conference on Electrical Machines and Systems (ICEMS), Harbin, China, pp. 1–5 (2019), DOI: 10.1109/ICEMS.2019.8922162.
[4] LiY.,Wu H.,Xu X., CaiY., Sun X., Analysis on electromechanical coupling vibration characteristics of in-wheel motor in electric vehicles considering air gap eccentricity, Archives of Electrical Engineering, vol. 5, pp. 851–862 (2019), DOI: 10.24425/bpasts.2019.130882.
[5] Lundin U., Wolfbrandt A., Method for Modeling Time-Dependent Nonuniform Rotor/Stator Configurations in Electrical Machines, IEEE Transactions on Magnetics, vol. 45, iss. 7, pp. 2976–2980 (2009), DOI: 10.1109/TMAG.2009.2015052.
[6] Zhang M., Macdonald A., Tseng K.-J., Burt G.M., Magnetic Equivalent Circuit Modeling for Interior Permanent Magnet Synchronous Machine under Eccentricity Fault, 48th International Universities’ Power Engineering Conference (UPEC), Dublin, Ireland, pp. 1–6 (2013), DOI: 10.1109/UPEC.2013.6715044.
[7] Ebrahimi B.M., Faiz J., Roshtkhari M.J., Static-, Dynamic-, and Mixed- Eccentricity Fault Diagnoses in Permanent-Magnet Synchronous Motors, IEEE Transactions on industrial electronics, vol. 56, no. 11, pp. 4727–4739 (2009), DOI: 10.1109/TIE.2009.2029577.
[8] Rosero J.A., Cusido J., Garcia A., Ortega J.A., Romeral L., Broken Bearings and Eccentricity Fault Detection for a Permanent Magnet Synchronous Motor, 32nd Annual Conference on IEEE Industrial Electronics (IECON), Paris, France, pp. 964–969 (2006), DOI: 10.1109/IECON.2006.347599.
[9] Ilamparithi T., Nandi S., Saturation independent detection of dynamic eccentricity fault in salient-pole synchronous machines, IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives (SDEMPED), Valencia, Spain, pp. 336–341 (2013), DOI: 10.1109/DEMPED.2013.6645737. [10] Goktas T., Zafarani M., Akin B., Discernment of Broken Magnet and Static Eccentricity Faults in Permanent Magnet Synchronous Motors, IEEE Transactions on Energy Conversion, vol. 31, iss. 2, pp. 578–587 (2016).
[11] Coenen I., van der Giet M., Hameyer K., Manufacturing Tolerances: Estimation and Prediction of Cogging Torque Influenced by Magnetization Faults, IEEE Transactions on Magnetics, vol. 48, iss. 5, pp. 1932–1936 (2012), DOI: 10.1109/TMAG.2011.2178252.
[12] Gasparin L., Fiser R., Cogging torque sensitivity to permanent magnet tolerance combinations, Archives of Electrical Engineering, vol. 62, pp. 449–461 (2013), DOI: 10.2478/aee-2013-0036.
[13] International Organization for Standardization, ISO 1940-1: Mechanical vibration — Balance quality requirements for rotors in a constant (rigid) state, Geneva, Switzerland (2003).
[14] https://www.smalley.com/wave-springs/bearing-preload, accessed March 2020.
[15] Henrotte F., Felden M., van der Giet M., Hameyer K., Electromagnetic force computation with the Eggshell method, 14th International Symposium on Numerical Field Calculation in Electrical Engineering (IGTE), Graz, Austria (2010).
[16] Herold T., Franck D., Schröder M., Böhmer S., Hameyer K., Transientes Simulationsmodell für die akustische Bewertung elektrischer Antriebe, e & i Elektrotechnik und Informationstechnik, vol. 133, no. 2, pp. 55–64 (2016).

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Authors and Affiliations

Markus Jaeger
1
Pascal Drichel
2
Michael Schröder
1
Joerg Berroth
2
Georg Jacobs
2
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Germany
  2. Institute of Systems Engineering and Machine Elements (MSE), RWTH Aachen University, Germany
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Abstract

Varying ohmic loss in the winding of electrical machines, which are operated at various operating points, results in temperature changes during operation. Particularly, when the temperature is varying dynamically, the insulation system suffers from repeated thermalmechanical stress, since the thermal expansion coefficients of the insulating materials and copper conductors are different. For the appropriate design of an insulation system, the effect of thermal-mechanical stress must be known. In the present work, motorettes are subjected to repeated thermal cycles. The expected lifetime is estimated and compared to the lifetime which is achieved by applying a lifetime-model which only considers thermal aging while ignoring thermal-mechanical stress effects. In addition, the hotspot temperature is simulated, the lifetime at the hotspot is estimated as theworst case. As expected, the results indicate that the thermal-mechanical stress plays a significant role during dynamic thermal aging of the winding insulation system. To better understand the thermal-mechanical stress effect, the resulting thermal-mechanical stress in a single wire is analyzed by the finite element method. A preliminary analysis of the aging mechanism of materials due to cyclic thermal-mechanical stress is performed with the theory of material fatigue.
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Bibliography

[1] Stone G.C., Boulter E.A., Culbert I., Dhirani H., Electrical insulation for rotating machines: design, evaluation, aging, testing, and repair, John Wiley & Sons (2004).
[2] Rothe R., Hameyer K., Life expectancy calculation for electric vehicle traction motors regarding dynamic temperature and driving cycles, 2011 IEEE International Electric Machines and Drives Conference (IEMDC), Niagara Falls, ON, Canada, pp. 1306–1309 (2011).
[3] Huang Z., Modeling and testing of insulation degradation due to dynamic thermal loading of electrical machines, Licentiate Thesis, Lund University, Lund (2017).
[4] Chen W., Nelson C., Thermal stress in bonded joints, IBM Journal of Research and Development, vol. 23, no. 2, pp. 179–188 (1979).
[5] Arrhenius S., On the heat of dissociation and the influence of temperature on the degree of dissociation of the electrolytes, Zeitschrift für Physikalische Chemie (in German, Über die Dissociationswärme und den Einfluss der Temperatur auf den Dissociationsgrad der Elektrolyte), vol. 4, no. 1, pp. 96–116 (1889).
[6] Dakin T.W., Electrical insulation deterioration treated as a chemical rate phenomenon, Transactions of the American Institute of Electrical Engineers, vol. 67, no. 1, pp. 113–122 (1948).
[7] Ruf A., Pauli F., Schröder M., Hameyer K., Lifetime modelling of non-partial discharge resistant insulation systems of electrical machines in dynamic load collectives, e & i Elektrotechnik und Informationstechnik (in German, Lebensdauermodellierung von nicht-teilentladungsresistenten isoliersystemen elektrischer maschinen in dynamischen lastkollektiven), vol. 135, no. 2, pp. 131–144 (2018).
[8] Pauli F., Schröder M., Hameyer K., Design and evaluation methodology for insulation systems of low voltage drives with preformed coils, 2019 9th International Electric Drives Production Conference (EDPC), Esslingen, Germany, pp. 1–7 (2019).
[9] Madonna V., Giangrande P., Lusuardi L., Cavallini A., Gerada C., Galea M., Thermal overload and insulation aging of short duty cycle, aerospace motors, IEEE Transactions on Industrial Electronics, vol. 67, no. 4, pp. 2618–2629 (2019).
[10] Sciascera C., Galea M., Giangrande P., Gerada C., Lifetime consumption and degradation analysis of the winding insulation of electrical machines, 2016 8th IET International Conference on Power Electronics, Machines and Drives (PEMD), Glasgow, UK, pp. 1–5 (2016).
[11] IEC 60505, Evaluation and qualification of electrical insulation systems (2011).
[12] Ruf A., Paustenbach J., Franck D., Hameyer K., A methodology to identify electrical ageing of winding insulation systems, 2017 IEEE International Electric Machines and Drives Conference (IEMDC), Miami, FL, USA, pp. 1–7 (2017).
[13] Pauli F., Ruf A., Hameyer K., Low voltage winding insulation systems under the influence of high du/dt slew rate inverter voltage, Archives of Electrical Engineering, vol. 69, no. 1, pp. 187–202 (2020).
[14] IEC 60034–18–41, Rotating electrical machines – Part 18–41: Partial discharge free electrical insulation system (Type I) used in rotating electrical machines fed from voltage converters – Qualification and quality control tests (2014).
[15] Nikolova G., Ivanova J., Interfacial shear and peeling stresses in a two-plate structure subjected to monotonically increasing thermal loading, Journal of Theoretical and Applied Mechanics, vol. 51 (2013).
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Authors and Affiliations

Liguo Yang
1
ORCID: ORCID
Florian Pauli
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Schinkelstraße 4, 52062 Aachen, Germany
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Abstract

Due to speed-dependent centrifugal forces, the support of the torque, static mechanical stress introduced by manufacturing processes the laminated core of rotating electrical machines is exposed to considerable mechanical stress. The resulting stress distribution changes the magnetic properties of the electrical steel. To take this into account, a magnetization model is constituted on the basis of vector magneto-mechanical measurements that include the magnetic permeability as a function of the mechanical stress and the angle between magnetization - and the maximum principal stress direction. Subsequently, the model is integrated into the finite element simulation of a permanent magnet excited synchronous machine at different rotational speeds.
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Authors and Affiliations

Benedikt Schauerte
1
ORCID: ORCID
Xiao Xiao
1
Kevin Jansen
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Schinkelstr. 4, D-52062 Aachen, Germany
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Abstract

Rare-earth permanent magnets are coated in order to avoid corrosion. When considering the rated geometrical properties of a sample, the coating thickness has to be known precisely as it wrongly enlarges the magnetically active volume which in turn affects the accuracy of the measured magnetic properties. In this work, the sensitivity of hard magnetic material property measurements regarding the consideration of different coating thicknesses is evaluated. Moreover, the impact of eddy current effects on the magnetic properties is studied when measuring in an open circuit. Additionally, an outlook for a measurement-based determination of the electric conductivity of permanent magnet samples is given.
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Authors and Affiliations

Alexander Kern
1
ORCID: ORCID
Nora Leuning
1
ORCID: ORCID
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Schinkelstr. 4, D-52062 Aachen, Germany
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Abstract

An integration of the electrical machine and the gearbox is attracting particular attention for the design of modern electric and hybrid drive trains, since it saves overall space and subsequently increases the power density. Another benefit of a high level of integration is that it enables a combined application of oils as both cooling fluid for the electrical machine and as lubrication fluid for the transmission system. In this way, the power density of the integrated drive train can be further increased. During the oil cycling, conductive contaminations may be introduced and subsequently have an influence on the function of the insulation system of the electrical machine. In the present work, the influences of the cooling oil and its conductive contaminations, conductive particles as well as their combination with humidity, on the electrical and dielectric properties of the insulation system are studied. The results show that by application of the cooling oil, the partial discharge inception voltage (PDIV) of the winding insulation increases significantly so that an electrical breakdown is prone to happen before a partial discharge (PD) occurs. With increasing particle contamination, the PDIV of the insulation system decreases significantly, while the capacitance increases. Besides, conductive particles and humidity decrease the surface resistance and surface breakdown voltage of the insulation papers significantly. The results indicate that the conductive particle contaminations can play an important role for the electrical degradation of the insulation system.
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Bibliography

[1] Lehmann R., Petuchow A., Moullion M., Künzler M., Windel C., Gauterin F., Fluid Choice Based on Thermal Model and Performance Testing for Direct Cooled Electric Drive, Energies, vol. 13, no. 22, 5867 (2020), DOI: 10.3390/en13225867.
[2] Popescu M., Staton D.A., Boglietti A., Cavagnino A., Hawkins D., Goss J., Modern heat extraction systems for power traction machines – A review, IEEE Transactions on Industry Applications, vol. 52, no. 3, pp. 2167–75 (2016), DOI: 10.1109/TIA.2016.2518132.
[3] Tighe C., Gerada C., Pickering S., Assessment of cooling methods for increased power density in electrical machines, 2016 XXII international conference on electrical machines (ICEM), Lausanne, Switzerland, pp. 2626–2632 (2016), DOI: 10.1109/ICELMACH.2016.7732892.
[4] Ponomarev P., Polikarpova M., Pyrhönen J., Thermal modeling of directly-oil-cooled permanent magnet synchronous machine, 2012 XXth International Conference on Electrical Machines, Marseille, France, pp. 1882–1887 (2012), DOI: 10.1109/ICElMach.2012.6350138.
[5] Dan M., Hao J., Qin W., Liao R., Zou R., Mengzhao Z., Liang S., Effect of different impurities on motion characteristics and breakdown properties of insulation oil under DC electrical field, 2018 IEEE International Conference on High Voltage Engineering and Application (ICHVE), Athens, Greece, pp. 1–4 (2018), DOI: 10.1109/ICHVE.2018.8642256.
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Authors and Affiliations

Liguo Yang
1
ORCID: ORCID
Florian Pauli
1
Shimin Zhang
2
Fabian Hambrecht
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Aachen, Germany
  2. Lubricant Division, TotalEnergies One Tech Solaize, France

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