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  • 1.
    Acquaviva,, Alessandro
    et al.
    Chalmers University of Technology, Department of Electrical engineering, Göteborg, Sweden.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Grunditz, Emma
    Chalmers University of Technology, Department of Electrical engineering, Göteborg, Sweden.
    Lundmark, Sonja
    Chalmers University of Technology, Department of Electrical engineering, Göteborg, Sweden.
    Thiringer, Torbjörn
    Computationally efficient modeling of electrical machines with cooling jacketIngår i: Artikel i tidskrift (Refereegranskat)
  • 2.
    Bessman, Alexander
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Soares, Rúdi Cavalerio
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Svens, P.
    Investigating the aging effect of current ripple on lithium-ion cells2015Ingår i: ECS Transactions, Electrochemical Society, 2015, Vol. 69, nr 18, s. 101-106Konferensbidrag (Refereegranskat)
    Abstract [en]

    We have built an experimental setup which exposes twelve cells to a well-defined ripple current. It consists of a system for cycling high capacity cells in parallel with a triangular current waveform superimposed on top of the direct current. The frequency of the waveform is variable up to 50 Hz, and the sum of the DC and AC components can have a magnitude of -40 A to 40 A. Current is measured over a 500 μω shunt resistor. The voltage and current of each cell is read simultaneously at a sample rate up to 4 MS/s, allowing for precise impedance measurements even for high frequency harmonics. The cells are cycled at 40 °C. The experiment has been designed to eliminate indirect effects of the AC harmonics as far as possible. This system is being used to test whether or not AC harmonics affect Li-ion aging.

  • 3.
    Bessman, Alexander
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Soares, Rúdi
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Vadivelu, Sunilkumar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Svens, Pontus
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Challenging Sinusoidal Ripple-Current Charging of Lithium-Ion Batteries2018Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, nr 6, s. 4750-4757Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sinusoidal ripple-current charging has previously been reported to increase both charging efficiency and energy efficiency and decrease charging time when used to charge lithium-ion battery cells. In this paper, we show that no such effect exists in lithium-ion battery cells, based on an experimental study of large-size prismatic cells. Additionally, we use a physics-based model to show that no such effect should exist, based on the underlying electrochemical principles.

  • 4.
    Bessman, Alexander
    et al.
    KTH.
    Soares, Rúdi
    KTH.
    Wallmark, Oskar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Svens, Pontus
    KTH.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Aging effects of AC harmonics on lithium-ion cellsManuskript (preprint) (Övrigt vetenskapligt)
  • 5.
    Bessman, Alexander
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Soares, Rúdi
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Svens, Pontus
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Aging effects of AC harmonics on lithium-ion cells2019Ingår i: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 21, s. 741-749Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the vehicle industry poised to take the step into the era of electric vehicles, concerns have been raised that AC harmonics arising from switching of power electronics and harmonics in electric machinery may damage the battery. In light of this, we have studied the effect of several different frequencies on the aging of 28 Ah commercial NMC/graphite prismatic lithium-ion battery cells. The tested frequencies are 1 Hz, 100 Hz, and 1 kHz, all with a peak amplitude of 21 A. Both the effect on cycled cells and calendar aged cells is tested. The cycled cells are cycled at a rate of 1C:1C, i.e., 28 A during both charging and discharging, with the exception of a period of constant voltage at the end of every charge. After running for one year, the cycled cells have completed approximately 2000 cycles. The cells are characterized periodically to follow how their capacities and power capabilities evolve. After completion of the test about 80% of the initial capacity remained and no increase in resistance was observed. No negative effect on either capacity fade or power fade is observed in this study, and no difference in aging mechanism is detected when using non-invasive electrochemical methods of post mortem investigation.

  • 6.
    Daniel, Wanner
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Nybacka, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Experimental implementation of a fault handling strategy for electric vehicles with individual-wheel drives2016Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015, CRC Press, 2016, s. 147-152Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a fault handling strategy for electric vehicles with four individual-wheel drives, which are based on wheel hub motors. The control strategy to handle the faults is based on the principle of control allocation and is implemented in an experimental vehicle. Experimental tests has been performed with the experimental vehicle and with simulation. The results show that the directional stability of such a vehicle can be improved for the analysed manoeuvre and failure mode, and the tendencies of the experimental results correspond with the simulation results. It has been found that the lateral and yaw motion could be strongly improved. 

  • 7.
    Du-Bar, Christian
    et al.
    KTH.
    Mann, A.
    Wallmark, Oskar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Werke, M.
    Comparison of Performance and Manufacturing Aspects of an Insert Winding and a Hairpin Winding for an Automotive Machine Application2019Ingår i: 2018 8th International Electric Drives Production Conference, EDPC 2018 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, two stators with different winding concepts but with the same rotor of an interior permanent magnet synchronous machine (IPMSM) type are presented. Both concepts are investigated based on their performance and their respectively stator cost and stator manufacturing aspects for a yearly production rate of 1 million units.

  • 8.
    Dubar, Christian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Eddy Current Losses in a Hairpin Winding for an Automotive Application2018Ingår i: Proceedings - 2018 23rd International Conference on Electrical Machines, ICEM 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, s. 710-716Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is well known that the effect of eddy current loss increases with a greater cross-sectional area of a wire exposed to a time-varying magnetic field. When using hairpin windings instead of conventional windings, the cross-sectional area of the strands is increased. However, conductors inside a slot are exposed to several simultaneous sources of time-varying magnetic fields that induce eddy currents. The aim of this paper is to study the non-uniform current distributions and the origin of the eddy current losses in such strands, considering typical dimensions and frequencies that are found in an electrical machine for an automotive application.

  • 9. Hagbin, Saeid
    et al.
    Alukula, Mats
    Khan, Kashif
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Lundmark, Sonja
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Carlson, Ola
    An integrated charger for plug-in hybrid electric vehicles based on a special interior permanent magnet motor2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    For a plug-in hybrid electric vehicle (PHEV), the battery needs to be charged from the grid while the vehicle is parked. The traction system components are normally not engaged during the charging time so there is a possibility to use them in the charger system to develop an integrated charger. An innovative high power isolated three-phase bi-directional integrated charger with unit power factor operation is introduced for PHEVs based on a special configuration of the ac motor. The winding of the machine is re-arranged in charging mode to have a three-phase boost based high power battery charger. The system configuration, the device model (machine with multiple windings), traction and charging system functionality and charger control are presented in this paper.

  • 10. Hagbin, Saeid
    et al.
    Khan, Kashif
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Lundmark, Sonja
    Alukula, Mats
    Carlson, Ola
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Integrated chargers for EV's and PHEV's: Examples and new solutions2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    The battery is an important component in an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV) and it should be charged from the grid in a cost efficient, preferably fast and definitely safe way. The charger could be an on board or an off board charger. For an on board charger it is possible to use available hardware of the traction system, mainly the inverter and the electric motor, in the charger circuit. This is called an integrated charger. In this paper, different examples of integrated chargers are reviewed and explained. Additionally, other possible solutions of integrated chargers are described.

  • 11.
    Harnefors, Lennart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Hinkkanen, Marko
    School of Electrical Engineering, Aalto University, Espoo, Finland.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Guest editorial - Special issue on permanent-magnet synchronous reluctance machines and their applications2016Ingår i: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 10, nr 5, s. 311-Artikel, forskningsöversikt (Övrigt vetenskapligt)
  • 12.
    Hui, Zhang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Limitations and constraints of eddy-current loss models for interior permanent-magnet motors with fractional-slot concentrated windings2017Ingår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper analyzes and compares models for predicting average magnet losses in interior permanent-magnet motors with fractional-slot concentrated windings due to harmonics in the armature reaction (assuming sinusoidal phase currents). Particularly, loss models adopting different formulations and solutions to the Helmholtz equation to solve for the eddy currents are compared to a simpler model relying on an assumed eddy-current distribution. Boundaries in terms of magnet dimensions and angular frequency are identified (numerically and using an identified approximate analytical expression) to aid the machine designer whether the more simple loss model is applicable or not. The assumption of a uniform flux-density variation (used in the loss models) is also investigated for the case of V-shaped and straight interior permanent magnets. Finally, predicted volumetric loss densities are exemplified for combinations of slot and pole numbers common in automotive applications.

  • 13. Jansson, Magnus
    et al.
    Harnefors, L.
    Wallmark, Oskar
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Synchronization at startup and stable rotation reversal of sensorless nonsalient PMSM drives2006Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 53, nr 2, s. 379-387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a variant of the well-known voltage model is applied to rotor position estimation for sensorless control of nonsalient permanent-magnet synchronous motors (PMSMs). Particular focus is on a low-speed operation. It is shown that a guaranteed synchronization from any initial rotor position and stable reversal of rotation can be accomplished, in both cases under load. Stable rotation reversal is accomplished by making the estimator insensitive to the stator resistance. It is also shown that the closed-loop speed dynamics are similar to those of a sensored drive for speeds above approximately 0.1 per unit, provided that the model stator inductance is underestimated. Experimental results support the theory.

  • 14.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Analysis of power losses in power MOSFET based stacked polyphase bridges converters2016Ingår i: 2016 IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia), Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 3050-3055Konferensbidrag (Refereegranskat)
    Abstract [en]

    The ability to accurately predict power semiconductor losses is essential for converter design and can provide a reference for thermal management. Based on a stacked polyphase bridges converter, a simplified but accurate loss model is used in this paper to calculate the power losses of power MOSFETs and experimentally verified. A special focus of the analysis is the ringing loss calculation since it is inevitable in the switching process of power MOSFETs. In addition, this paper presents a comparison of power losses between Si MOSFET and GaN FET based converters by using the analytical model.

  • 15.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Serial communication based distributed control of the stacked polyphase bridges converter2016Ingår i: 8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016), IET , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In recent years, the stacked polyphase bridges converter has gained increasing interest due to its modularity and scalability for different power and voltage levels. To maintain the advantages from this architecture, distributed control system is required instead of centralized control system. A serial communication protocol based distributed control architecture for an SPB converter consisting of four submodules is presented and experimentally verified in this paper. Moreover, the sensitiveness of the distributed control system to modulation effect, communication delay, and communication speed is also investigated.

  • 16.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Apostolopoulos, Nikolaos
    Communication-Based Distributed Control of the Stacked Polyphase Bridges Converter2018Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, nr 2, s. 1011-1020Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stacked polyphase bridges converter has gained increasing interest in recent years due to its modular design and easy adaption to different power levels. The real-time control and dynamic data transmission of a stacked polyphase bridges converter consisting of a number of submodules are challenging tasks. For the reason that the distributed control architecture can maintain the benefit of modularity, such an approach dedicated for the stacked polyphase bridges converter is presented in this paper. Suitable communication techniques and synchronization techniques for the presented architecture are discussed. In addition, based on a dynamic model of the converter, the sensitiveness of the distributed control system to communication bandwidth and delay is studied on an experimental prototype.

  • 17.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Apostolopoulos, Nikolaos
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Modulation and Power Losses of a Stacked Polyphase Bridges Converter2017Ingår i: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, E-ISSN 2168-6785, Vol. 5, nr 1, s. 409-418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents and analyzes modulation and power losses of a stacked polyphase bridges converter - a modular topology potentially allowing increased compactness and fault tolerance for automotive drive systems. In particular, an analysis of the impact of modulation on the harmonic content of the dc-link current of the converter is made. Due to the possibility of using higher switching frequency devices, the current ripple of the stacked polyphase bridges converter can be smaller than that of the two-level three-phase converter with the same dclink capacitor. However, higher switching frequency will result in higher switching losses per fundamental period. Therefore, this paper also investigates the reduction in the dc-link ripple current achieved by interleaving the modulation between the different converter submodules. The amount of reduction can be predicted using an analytical model whose results are demonstrated to be in good agreement with results from corresponding simulations and from an experimental setup. Furthermore, based on the experimentally verified analysis, the stacked polyphase bridges converter in a typical automotive drive system is discussed and compared to a conventional two-level three-phase converter.

  • 18.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nikouei Harnefors, Mojgan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Control and modulation of the stacked polyphase bridges inverter2014Ingår i: IEEE Energy Conversion Congress and Exposition, IEEE, 2014, s. 3023-3029Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to meet the requirements of future electric vehicle (EV) drive systems, new converter topologies are required. The stacked polyphase bridges (SPB) inverter is a new topology which is well adapted to the needs for future EVs. In addition to low power losses, the SPB inverter also has fault tolerance ability and good dynamic behavior. This paper presents a further analysis of the control and modulation concept of the SPB inverter. Simulation results are used to verify the analysis conclusions.

  • 19.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Zhang, Hui
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Evaluation of a Multiphase Drive System in EV and HEV Applications2015Ingår i: 2015 IEEE INTERNATIONAL ELECTRIC MACHINES & DRIVES CONFERENCE (IEMDC), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 941-945Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multiphase machine drive systems have been applied in many electric propulsion fields such as aerospace and electric vehicle applications. With the development of SiC semiconductors, its superior characteristic makes compact multiphase converters possible. Moreover, by using a single chip in each switch, problems caused by an uneven current split between paralleled devices can be avoided. This paper presents a performance evaluation for a 50 kW multiphase EV/HEV drive system with 1.2 kV SiC MOSFETs. Power loss calculation, cost comparison and system simulation are provided to illustrate the feasibility of the proposed concept.

  • 20.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Staffan, Norrga
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Communication-based distributed control of the stacked polyphase bridges converterIngår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stacked polyphase bridges (SPB) converter has gained increasing interest in recent years due to its modular design and easy adaption to different power levels. The realtime control and dynamic data transmission of an SPB converter consisting of a number of submodules are challenging tasks. For the reason that the distributed control architecture can maintain the benefit of modularity, such an approach, dedicated for the SPB converter is presented in this paper. Suitable communication techniques and synchronization techniques for the presented architecture are discussed. In addition, based on a dynamic model of the converter, the sensitiveness of the distributed control system to communication bandwidth and delay is studied on an experimental prototype.

  • 21.
    Jin, Lebing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Zhang, Hui
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Comparison and Evaluation of Modular Integrated Electric Drives for Automotive Traction ApplicationsIngår i: IEEE Transactions on Transportation Electrification, ISSN 2332-7782Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to increase the competitiveness of the integrated motor drives (IMDs), alternative topologies have been developed for electric and hybrid electric vehicles. Within this framework, the integrated modular motor drive (IMMD) concept has been proposed, aiming to make the system more compact and fault-tolerant. Potential converter topologies for an IMMD are reviewed in this paper, with particular focus on the stacked polyphase bridges converter, the parallel-connected polyphase bridges converter and the modular high frequency converter. The machine topologies that are the best candidates to be used in such drive systems are also presented. Based on the FreedomCar 2020 specifications, a comparative evaluation of the studied topologies is presented and discussed in terms of machine design, power losses, energy storage requirements, and cell redundancy. The conventional two-level three-phase drive system is utilized as the reference. Finally, predicted costs of the studied drive systems are compared for both fault-tolerant designs and non-fault tolerant designs.

  • 22. Jonasson, Mats
    et al.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Centrum för elkraftteknik, EKC2.
    Control of electric vehicles with autonomous corner modules: implementation aspects and fault handling2008Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 3, nr 3, s. 213-228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, vehicle dynamics for electric vehicles equipped with in-wheel motors and individual steering actuators are studied adopting the principles of optimal tyre-force allocation. A simple method for describing the constraints owing to tyre and actuator limitations is described. The control architecture is evaluated by investigating its response to realistic fault conditions. The evaluation demonstrates that the control architecture's ability to ensure vehicle stability generally is good. However, during major faults and extreme driving situations, vehicle stability is not maintained unless the constraints in the optimisation process used for tyre-force allocation are adapted to the specific fault.

  • 23.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Wallmark, Oskar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Stability of an electric vehicle with permanent magnet in-wheel motors during electrical faults2007Ingår i: World Electric Vehicle Journal, ISSN 2032-6653, E-ISSN 2032-6653, Vol. 1, s. 100-107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an analysis of the stability of an electric vehicle equipped with in-wheel motors of permanent-magnet type during a class of electrical faults. Due to the constant excitation from the permanent magnets, the output torque from a faulted wheel cannot easily be removed if an inverter shuts down, which directly affects the vehicle stability. In this paper, the impact of an electrical fault during two driving scenarios is investigated by simulations; using parameters from a 30 kW in-wheel motor and experimentally obtained tire data. It is shown that the electrical fault risks to seriously degrading the vehicle stability if the correct counteraction is not taken quickly. However, it is also demonstrated that vehicle stability during an electrical fault can be maintained with only minor lateral displacements when a closed-loop path controller and a simple method to allocate the individual tire forces are used. This inherent capacity to handle an important class of electrical faults is attractive; especially since no additional fault-handling strategy or hardware is needed.

  • 24.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Stability of an electric vehicle with permanent-magnet in-wheel motors during electrical faults2006Konferensbidrag (Refereegranskat)
  • 25.
    Khan, Kashif
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Haghbin, Saeid
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Design and performance analysis of a permanent-magnet assisted synchronous reluctance machine for an integrated charger application2010Ingår i: 19th International Conference on Electrical Machines, ICEM 2010, 2010, s. 5607905-Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a plug-in hybrid electric vehicle equipped with an integrated charger, the electric machine and the inverter, which in traction mode are used to propel the vehicle and recover energy during braking, are also used to charge the battery from the grid while the vehicle is at rest [1]. This paper studies the design and performance of a permanent-magnet assisted synchronous reluctance machine (PMaSynRM) both in traction and charging mode. Designing a PMaSynRM in order to obtain optimal reluctance and magnetic torque components is a complex task since rotor dimensioning for one torque component (magnet or reluctance torque) limits the possibility to optimize the other torque component. This paper identifies and relates the design parameters that influence these torque components and the performance of the machine using simulations based on the finite element method. The results are compared based on developed torque, torque ripple and relative values of the resulting magnet and reluctance torque.

  • 26.
    Khan, Kashif
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Design aspects on magnet placement in permanent-magnet assisted synchronous reluctance machines2010Ingår i: IET Conference Publications, Institution of Engineering and Technology, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    The design of permanent-magnet assisted synchronous reluctance machines (PMRSMs) for optimum reluctance and magnetic torque components is a complex task since rotor dimensioning for one torque component (magnet or reluctance torque) limits the possibility to optimize the other torque component. This paper identifies and relates the design parameters that influence these torque components. It describes the influence of insulation ratio, magnet size and magnet placement on the performance of the machine using finite element (FEM) based simulations. The results are compared based on developed torque, torque ripple and relative values of the resulting magnet and reluctance torque.

  • 27.
    Krings, Andreas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Mousavi, Seyedali
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Temperature Influence of NiFe Steel Laminations on the Characteristics of Small Slotless Permanent Magnet Machines2013Ingår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 49, nr 7, s. 4064-4067Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High performance electrical machines can operate at temperatures of 100 degrees C and beyond in rotor and stator cores. However, magnetic properties are generally measured at room temperatures around 23 degrees C to 25 degrees C according to the standards, even if it is known that the magnetization of some materials is substantially influenced by increasing temperatures. This paper investigates the thermal influence on the magnetic properties and iron losses in the stator cores of small slotless permanent magnet synchronous machines (PMSMs). The stator stack is made of thin nickel iron (NiFe) lamination sheets. Magnetic measurements of the stator core are conducted for different frequencies and flux densities at several temperatures between 25 degrees C and 105 degrees C. The obtained measurement data is afterwards used in finite element method (FEM) simulations to investigate the influence of the magnetic property change on the machine performance. For the PMSM in consideration, the FEM simulations show that an increased stator core temperature reduces the electromagnetic torque considerably; approximately 1/3 of the torque reduction due to increased rotor magnet and stator core temperatures (from 25 degrees C to 100 degrees C) can be attributed to the increased stator core temperature.

  • 28.
    Krings, Andreas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nategh, Shafigh
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Stening, Alexander
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Grop, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Measurement and Modeling of Iron Losses in Electrical Machines (Invited Paper)2012Ingår i: Proceedings of the 5th International Conference Magnetism and Metallurgy WMM'12, Gent, Belgium: Gent University , 2012, s. 101-119Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This paper gives an overview of nowadays used simulation models and measurement methods in order to determine iron losses in electrical machinery. The paper provides machine designers and system engineers with an overview of suitable iron loss models applicable for the machine design process and simulations. Furthermore, possible methods for iron loss measurements in electrical machines are presented from ongoing research projects. Besides standard electrical power measurements, iron losses are determined by thermal and magnetic property measurements, taking into account different IEC and IEEE standards.The goal is to emphasize the different possibilities of iron loss measurement methods and possible application areas for electrical machinery.

  • 29.
    Krings, Andreas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nategh, Shafigh
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Influence of the Welding Process on the Magnetic Properties of a Slot-less Permanent Magnet Synchronous Machine Stator Core2012Ingår i: Proceedings of the 2012 XXth International Conference on Electrical Machines, IEEE conference proceedings, 2012, s. 1331-1336Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, the influence of the welding processduring the manufacturing of small, slot-less permanent magnetsynchronous machines (PMSMs) is studied. The focus lies onthe change of the magnetic properties and the iron losses inthin, high quality Si-alloyed electrical steel sheets (NO 20). It isshown that the welding process changes the magnetic materialproperties significantly and increases the specific iron losses.Experimental results are provided for magnetic flux densitiesup to 1.3 T and frequencies in the range of 0.1Hz to 200Hz.

  • 30.
    Krings, Andreas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nategh, Shafigh
    SmartMotor AS, Rolls-Royce Group, Norway .
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Influence of the Welding Process on the Performance of Slotless PM Motors With SiFe and NiFe Stator Laminations2014Ingår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 50, nr 1, s. 296-306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the welding process during the manufacturing of small slotless permanent-magnet synchronous machines (PMSMs) is studied in this paper. The focus lies on the change of the magnetic properties in high-quality silicon-iron (SiFe) and nickel-iron (NiFe) electrical steel sheets with thicknesses of 0.1 and 0.2 mm. It is shown that the welding process changes the magnetic material properties significantly and increases the specific iron losses. Experimental results are provided for magnetic flux densities up to 1.5 T and frequencies from quasi-static to 200 Hz. The obtained measurement data is afterward used in finite-element method (FEM) simulations to investigate the influence of the magnetic property changes on the motor performance, particularly with regard to stator core losses.

  • 31.
    Krings, Andreas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nategh, Shafigh
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Local Iron Loss Identification by Thermal Measurements on an Outer-Rotor Permanent Magnet Synchronous Machine2012Ingår i: Proceedings of the 15th International Conference on Electrical Machines and Systems (ICEMS 2012), Sapporo: Institution of Electrical Engineers of Japan (IEEJ), 2012, s. 6401970-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the experimental determination of iron losses in an outer-rotor permanent magnet synchronous machine (PMSM) by using an inverse thermal model (ITM) in connection with transient thermal measurements. First, the theory and assumptions lying behind the method are presented. Afterwards, 3D finite element method (FEM) based simulations are used to determine the flux density distribution and iron losses in the magnetic steel parts of the investigated machine. Thermal measurements are conducted to determine local iron losses in the stator tooth tips using the ITM. Finally, measurement and FEM simulation results are compared.

  • 32.
    Krings, Andreas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Influence of PWM Switching Frequency and Modulation Index on the Iron Losses and Performance of Slot-less Permanent Magnet Motors2013Ingår i: Proceedings of the 16th International Conference on Electrical Machines and Systems, Busan: KIEE - The Korean Institute of Electrical Engineering , 2013, s. 474-479Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the influence of switching frequency and modulation index on the iron losses in thin silicon-iron (SiFe) lamination sheets of a small slot-less permanent magnet synchronous machine (PMSM). First, measurements are conducted on one welded and one non-welded stator core for switching frequencies between 1 kHz and 20 kHz and modulation indices of 0.4, 0.7, and 0.9, keeping constant fundamental flux density peak values. The obtained measurement data is afterwards used in finite element method (FEM) simulations to investigate the switching frequency influenceon the performance of the PMSM.

  • 33.
    Krings, Andreas
    et al.
    ABB AB Corporate Research, Sweden .
    Soulard, Juliette
    ABB AB Corporate Research, Sweden .
    Wallmark, Oskar
    ABB AB Corporate Research, Sweden .
    PWM Influence on the Iron Losses and Characteristics of a Slot-less Permanent Magnet Motor with SiFe and NiFe Stator Cores2015Ingår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, nr 2, artikel-id 6891228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the influence of switching frequency and modulation index combined with welding on the iron losses in thin silicon-iron and nickel-iron lamination sheets of a small slot-less permanent magnet synchronous machine. First, measurements are conducted on welded and non-welded stator ring cores for switching frequencies between 1 kHz and 20 kHz and modulation indices of 0.4, 0.7, and 0.9, keeping constant fundamental flux density peak values. This is possible by changing the DC link voltage of the inverter. The obtained measurement data is afterwards used in finite element method (FEM) simulations to investigate the inverter influence on the performance of the permanent magnet synchronous machine.

  • 34.
    Millinger, Jonas
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik. Atlas Copco Industrial Technique AB.
    Bacco, Giacomo
    Manzolini, Virginia
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bianchi, Nicola
    Design and Evaluation of a Short-Circuit Rotor-Ring for Enhanced Self-Sensing Capability in a Slotless PM Motor2019Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper deals with the design and evaluation of a short-circuit rotor-ring for enhanced self-sensing capability in a 2-pole slotless permanent-magnet motor. High-frequency rotor anisotropy is enabled by adding as hort-circuited rotor-ring. Optimal ring-dimensions are determined by parametric numerical studies. An effective high-frequency saliency of up to 1.8 is demonstrated. The steady-state estimation error is within ±2◦, practically unaffected by current level (in contrast to slotted self-sensing electrical machinery) due to the large effective air-gap. The proposed observer performs properly also during dynamic load changes. Fall-times from 3000 to 0 rpm in less than 50 ms with negligible overshoot are demonstrated. Also parasitic effects such as power losses, heating and torque ripple are analyzed.

  • 35.
    Millinger, Jonas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Influence of Shaft Relative Permeability on Rotor Losses in 2-pole Slotless High-Speed Motor2016Ingår i: Proceedings - 2016 22nd International Conference on Electrical Machines, ICEM 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 405-411, artikel-id 7732558Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a time-efficient transient numerical method for three-dimensional analysis of rotor losses in a three-phase 2-pole high-speed permanent-magnet synchronous machine. The motor has axially stacked ring shaped permanent magnets (PM). The influence of shaft material properties on rotor harmonic losses and loss distribution between the rotor shaft and magnets is investigated in the frequency range 10100 kHz. It is found that the shaft magnetic properties have a significant impact not only on the total rotor losses, but on the magnet losses and inductance as well.

  • 36.
    Millinger, Jonas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Soulard, J.
    Influence of lamination thickness on harmonic losses in 2-pole slotless permanent-magnet motors2017Ingår i: 2017 IEEE International Electric Machines and Drives Conference, IEMDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 8002064Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an original theoretical and experimental investigation of the iron losses for three different commercially available non-oriented silicon-iron (SiFe) steel grades (with lamination thicknesses 0.1, 0.2 and 0.3 mm) in a 2-pole slotless permanent magnet motor. The study is conducted over a wide frequency range (10-100 kHz), which is a novelty. The corresponding winding losses are succesfully identified for this purpose. The impact of temperature is also studied. The results show that that iron losses compose a significant share of the total losses beyond 50 kHz. Stator harmonic iron losses at 100 kHz can be decreased with 30% by using NO10 instead of NO30.

  • 37.
    Millinger, Jonas
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Soulard, J.
    Thermal Modeling of Slotless PM Motor for Industrial Hand Tools2018Ingår i: Proceedings - 2018 23rd International Conference on Electrical Machines, ICEM 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, s. 2695-2701Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a time-efficient steady-state thermal model for a slotless PM motor has been developed. Harmonic losses due to inverter supply are also considered, and the impact of different inverter configurations are investigated. The importance of concentric motor manufacturing process control (enabling a shorter air-gap) is demonstrated from a system point of view. The paper has shown that the total system weight can be reduced by 38 % without performance impairment by deploying a shorter air-gap and carefully considering the inverter configuration.

  • 38.
    Millinger, Jonas
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik. KTH.
    Wallmark, Oskar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Soulard, Juliette
    KTH.
    High Frequency Characterization of Losses in FullyAssembled Stators of Slotless PM Motors2018Ingår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract—The recent emerge of wide band-gap (WBG) powertransistors enables higher switching frequencies in electricalmotor drives. Their full utilization from a system point ofview requires quantification of the corresponding time-harmonicmotor losses. As an initial step, this paper presents a uniquestudy of stator losses for three different commercially availablenon-oriented silicon-iron (SiFe) steel grades (with laminationthicknesses 0.1, 0.2 and 0.3 mm). The investigations cover awide frequency range (10-100 kHz) at different levels of DC-bias(up to 1.6 T). Iron losses are identified from measurements onfully assembled stators, deploying a novel technique. By utilizingfully assembled stators, no additional samples are required.Manufacturing influence is inherently incorporated. Results showthat measured iron losses are twice as high at 10 kHz comparedto Epstein test results, which emphasizes the need to incorporatemanufacturing influence on iron losses at high frequencies. Thelevel of DC-bias is also observed to have a significant impacton iron losses (up to 30 %). Even though thinner laminationsare known for reducing iron losses, the reduction is much lowerthan anticipated in the studied frequency range due to skin effect.Using 0.1 mm lamination gauge instead of 0.3 mm reduces lossesby 50 % at 10 kHz, while the same substitution at 100 kHz onlyreduces losses by 30 %. Future work includes loss separation incomplete converter-fed machines.

  • 39.
    Nategh, Shafigh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Huang, Zhe
    Krings, Andreas
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Thermal Modeling of Directly Cooled Electric Machines Using Lumped Parameter and Limited CFD Analysis2013Ingår i: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, nr 4, s. 979-990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a practical approach to model thermal effects in directly cooled electric machines. The main focus is put on modeling the heat transfer in the stator winding and to the cooling system, which are the two critical parts of the studied machines from a thermal point of view. A multisegment structure is proposed that divides the stator, winding, and cooling system into a number of angular segments. Thereby, the circumferential temperature variation due to the nonuniform distribution of the coolant in the cooling channels can be predicted. Additionally, partial computational fluid dynamics (CFD) simulations are carried out to model the coolant flow in the cooling channels and also on the outer surface of the end winding bodies. The CFD simulation results are used as input to the analytical models describing the convective heat transfer to the coolant. The modeling approach is attractive due to its simplicity since CFD simulations of the complete machine are avoided. The proposed thermal model is evaluated experimentally on two directly cooled induction machines where the stator winding is impregnated using varnish and epoxy, respectively. A good correspondence between the predicted and measured temperatures under different cooling conditions and loss levels is obtained.

  • 40.
    Nategh, Shafigh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Huang, Zhe
    Lunds tekniska högskola.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Krings, Andreas
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Thermal Modeling of Directry Cooled Electric Machenes Using Lumped Parameter and Limited CFD AnalysisArtikel i tidskrift (Övrigt vetenskapligt)
  • 41.
    Nategh, Shafigh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Krings, Andreas
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Huang, Zhe
    Lunds tekniska högskola.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Lindenmo, Magnus
    Evaluation of stator and rotor lamination materials for thermal management of a PMaSRM2012Ingår i: Proceedings of the 20th International Conference on Electrical Machines, ICEM 2012, 2012, s. 1309-1314Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, the thermal impact of using different steel laminations in the stator and the rotor of a permanentmagnet assisted synchronous reluctance machine designed for an automotive application is studied. In this regard, two main parameters of the steel lamination materials, thickness and amount of alloy content in weight percent, are studied. Frequency characteristics of the iron losses of the studied materials are used to estimate iron losses in the stator and rotor laminations. An accurate lumped parameter model including a housing water jacket cooling system is used to model thermal effects and estimate the temperature distribution in critical parts of the machine. The predicted temperature distributions in the machines show that using lamination materials with different amounts of alloy content leads to 2%-10% variation in the temperatures of rotor and winding. However, using materials with different thicknesses results in substantial temperature changes in critical parts of the machine (up to 75%).

  • 42.
    Nategh, Shafigh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Krings, Andreas
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Evaluation of Impregnation Materials for Thermal Management of Liquid-Cooled Electric Machines2014Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, nr 11, s. 5956-5965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the thermal impact of using different impregnation materials on high-performance liquid-cooled electric machines is studied. In this regard, varnish, Epoxylite, and a silicone-based thermally conductive material are considered. To study thermal effects of using different impregnation materials in theory, an advanced lumped-parameter thermal model of the studied electric machines is developed. In addition to the simulation studies, three identical induction machines using the aforementioned materials are manufactured and evaluated. Experimental tests are carried out at a wide range of current magnitudes and cooling conditions. A good agreement between the temperature measurements and corresponding simulation results is observed. It is demonstrated that using innovative thermally conductive materials in the stator slots and the end winding bodies of liquid-cooled electric machines results in a significant reduction in the winding hot spot temperature. Additionally, the influence of the critical parameters on the impregnation material performance, e. g., impregnation goodness and slot fill factor, is studied.

  • 43. Nategh, Shafigh
    et al.
    Lassila, Viktor
    Huang, Zhe
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Evaluation of alternative stator and rotor lamination materials for thermal management of permanent magnet machines2011Konferensbidrag (Refereegranskat)
  • 44.
    Nategh, Shafigh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Thermal analysis of permanent-magnet synchronous reluctance machines2011Ingår i: 14th European Conference on Power Electronics and Applications, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a thermal analysis of permanent-magnet synchronous reluctance machines (PM-SRM). Particular focus is put on the rotor and two lumped parameter (LP) thermal models of the rotor are implemented and evaluated. The results of the two LP thermal models are compared to thermal simulations using the finite element method (FEM). Induced eddy current losses in the permanent magnets are computed using three-dimensional (3D) FEM computations whereas the losses in the electrical steel are obtained using a 2D FEM model. Based on type of cooling system, two cases are evaluated and the agreement between the two LP thermal simulations and the thermal FEM simulation is generally good but particular differences are highlighted. In the first case, the water cooling system manages to effectively handle the dominating copper losses which results in only a minor temperature difference between the shaft and the inner part of the stator teeth. In the second case, it is assumed that there is a significant temperature difference between the rotor shaft and the stator.

  • 45.
    Nategh, Shafigh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Zhao, Shuang
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Thermal Analysis of a PMaSRM Using Partial FEA and Lumped Parameter Modeling2012Ingår i: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 27, nr 2, s. 477-488Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an advanced lumped parameter (LP) thermal model for a permanent-magnet assisted synchronous reluctance machine (PMaSRM) developed for propulsion in a hybrid electric vehicle. Particular focus is put on the stator winding and a thermal model is proposed that divides the stator slot into a number of elliptical copper and impregnation layers. The model is enabled by the derivation of an approximate analytical expression for the thermal resistance of an elliptical cylinder with constant thickness. The approach is attractive due to its simplicity and the fact that it closely models the actual temperature distribution for common slot geometries. Additionally, an analysis, using results from a proposed simplified thermal finite element model representing only one slot of the stator and its corresponding end winding, is presented in which the number of layers and the proper connection between the parts of the LP thermal model representing the end winding and the active part of winding is determined. The presented thermal model is evaluated experimentally on a PMaSRM equipped with a water cooling jacket, and a good correspondence between the predicted and measured temperatures is obtained.

  • 46. Nategh, Shafigh
    et al.
    Zhang, Hui
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Aldo, Boglietti
    Nassen, Tobias
    Bombardier Transportat, SE-72214 Vasteras, Sweden.
    Bazant, Martin
    Bombardier Transportat, CH-8050 Zurich, Switzerland.
    Transient thermal modeling and analysis of railway traction motors2018Ingår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 66, nr 1, s. 79-89, artikel-id 8328892Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a practical approach to modeland analyze transient thermal effects in open air-cooled electrictraction motors. The developed thermal modeling method enablesaccurate estimation of temperature in critical parts of the motorincluding winding and bearing. Advantages of both numericaland analytical modelling methods are exploited with the aim ofrealizing accurate estimation of hot spot temperatures in tractionmotors while keeping the computation time within a reasonablerange. Computational fluid dynamics (CFD) simulations arecarried out to model the cooling fan’s performance and airflow distribution in the motor in order to provide heat transferboundary inputs to the developed combined finite element (FE)and lumped parameter (LP) thermal model. The combinationof the FE and LP models keeps the size of the model relativelysmall and enables running transient calculations reasonably fast.Also, the developed model provides the possibility to studythe influence of stator and rotor duct blockages on the motorthermal performance which is a common root of failure intraction applications during operation in dirty environments. Theproposed thermal model is verified using experimental results ona traction motor equipped with temperature sensors in motorcritical parts and a good agreement between estimated andmeasured temperatures is achieved. Finally, a calibrated fullyanalytical model using the abovementioned developed model isimplemented to further reduce simulation running time andcalculate motor temperature under normal running condition.

  • 47.
    Nategh, Shafigh
    et al.
    Smartmotor AS.
    Övrebö, Sigurd
    Smartmotor AS.
    Mahdavi, Sara
    Department of Electrical Machines, RWTH Aachen University, Germany.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Thermal modelling of a permanent magnet machine built using litz wire2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers thermal modeling of a 2 MW permanent magnet machine designed and manufactured for marine applications. The main focus is placed on the winding made of the Litz wire, and a practical approach to model heat transfer is presented. The proposed thermal modeling method, named segment-layer, is compared to traditional thermal models used mainly for standard winding configurations. In order to evaluate the accuracy of the developed thermal model, both simulation and experimental results are presented. In the simulation study, the proposed and traditional modeling methods are compared to a detailed finite element model of the Litz wire. Temperature measurements are carried out on the 2 MW machine prototype and a good agreement between the measurements and corresponding thermal model results is achieved. The suggested method is user-friendly and enables both analytical and numerical modeling of the Litz wire. Also, the parameters that play an important role in the winding heat transfer, e.g. impregnation goodness, can be easily implemented in the model developed in this paper.

  • 48.
    Nikouei Harnefors, Mojgan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES).
    Harnefors, Lennart
    KTH, Skolan för elektro- och systemteknik (EES).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES).
    Operation Under Fault Conditions of the Stacked Polyphase Bridges Converter2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    The stacked polyphase bridges converter consists of several submodules that, on the input dc side, all are connected in series. Whereas controller designs presented in previous studies have been found promising for realizing equal voltage sharing between submodules, the survival and stability under fault conditions have not been studied. This paper presents a control strategy that enables survival of the converter after the occurrence of a sudden short circuit of a single transistor switch. The results are verified by simulations.

  • 49.
    Nikouie Harnefors, Mojgan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Jin, Lebing
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Harnefors, Lennart
    ABB Corporate Research, Västerås, Sweden.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Analysis of the dc-link stability for the stacked polyphase bridges converter2015Ingår i: 2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe), IEEE , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an analysis of the capacitor voltage stability for a stacked polyphase bridges (SPB)

    type converter. The SPB converter comprises of several submodules which are connected in series.

    Therefore, stability of the dc-link voltage is very important to investigate. From the analysis, a corresponding

    controller and an analytical expression for stability are derived. The proposed controller and

    the associated stability condition are verified in a simulation environment and on a small experimental

    setup.

  • 50.
    Nikouie Harnefors, Mojgan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Jin, Lebing
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Harnefors, Lennart
    ABB, Corporate Research, Sweden.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    DC-link stability analysis and controller design for the stacked polyphase bridges converter2017Ingår i: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 32, nr 2, s. 1666-1674, artikel-id 7451258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stacked polyphase bridges (SPB) converter consists of several submodules that all are connected in series to a voltage source. The total dc-link voltage should split in a balanced way among the submodules. This does not always occur inherently. This paper presents an analysis of the capacitor voltage stability for the SPB converter. From the analysis, criteria for stability are derived and three alternatives of a suitable balancing controller are designed. The proposed controller alternatives and their associated stability properties are verified on an experimental setup and by simulation.

12 1 - 50 av 98
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