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  • 1.
    Abrahamsson, Curt Johan David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fregelius, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bladh, Johan
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Magnetic thrust bearing for a 10 MW hydropower generator with a Kaplan turbine2018Conference paper (Refereed)
  • 2.
    Evestedt, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Controlling airgap magnetic flux density harmonics in synchronous machines using field current injection2021In: Electrical engineering (Berlin. Print), ISSN 0948-7921, E-ISSN 1432-0487, Vol. 103, p. 195-203Article in journal (Refereed)
    Abstract [en]

    In this paper, a method to control the harmonic content of the magnetic flux density in the airgap of a synchronous machine is presented. Voltage harmonics in one phase as well as the exciting magnetic forces can be affected. Switched power electronics were used to provide the field current to a synchronous machine, the control added specific current harmonics to the DC field current in order to minimize either voltage harmonics or magnetic forces. The method is verified and compared with simulations and experiments on an existing electrical machine.

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  • 3.
    Evestedt, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Mitigation of Unbalanced Magnetic Pull in Synchronous Machines With Rotating Exciters2021In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 36, no 2, p. 812-819Article in journal (Refereed)
    Abstract [en]

    A magnetization system with active compensation of unbalanced magnetic pull for synchronous machines with rotating exciters is demonstrated. The system used switched power electronics and a digital control system to control the currents in four rotor pole groups, each consisting of 3 poles. It was mounted on the shaft of a synchronous machine, providing an interface between a permanent magnet outer-pole brushless exciter and the segmented field winding. Measurements of magnetic flux density on each pole face and current control made it possible to control the airgap magnetic flux density to balance the machine magnetically, thus removing flux density space harmonics in the airgap and also the unbalanced magnetic pull. The construction of the system is presented along with results from experiments and simulations. Tests were performed with the stator winding both in series and with two parallel circuits. Approximately 80% reduction of static forces and 60% reduction of dynamic forces between the stator and rotor were observed when the system was running.

  • 4.
    Evestedt, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jose. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. Johan. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Altering Flux Density Harmonics in the Air-gap of Synchronous Machines by Active Control of the Field CurrentIn: IEEE Transactions on Industrial Electronics, ISSN 0278-0046, E-ISSN 1557-9948Article in journal (Refereed)
    Abstract [en]

    Flux density harmonics in the air-gap of electrical machines create distorted voltage waveforms and can induce vibrations. These problems are difficult to mitigate when the machine is already in operation and therefore a lot of effort is made during the design phase to eliminate them. Still, many in-operation machines experience problems related to harmonics and often the solution is to mechanically reinforce and change modal shapes which is expensive and inconvenient. Using a current controlled switched power supply to excite a synchronous machine and adding specific harmonics to the DC-field current it is shown that it is possible to alter the harmonic content of the flux density in the air-gap, and thus affect  voltage harmonics and the exciting magnetic forces. The method is verified and compared with simulations and experiments on an existing electrical machine. 

  • 5.
    Felicetti, Roberto
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Pérez-Loya, Jesús J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Lundin, Claes U.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Simulation of Rapid Voltage Edge Related Voltage Surges in Highly Inductive Windings with Frequency Dependent Parameters2023In: Progress in Electromagnetics Research B, E-ISSN 1937-6472, Vol. 99, p. 1-21Article in journal (Refereed)
    Abstract [en]

    Many static and rotating electric energy converters make use of inductive coils as filters, reactive loads or exciters, where a sudden variation of the magnetizing current can produce severe overvoltage with potential subsequent insulation damage. In some applications the overvoltage is the result of a superposition of travelling voltage waves in a supplying line. Traditional tools for studying such phenomena are based on ordinary differential equations that can heavily handle variable parameters, especially if they change according to the rapidity of the observed overvoltage. In this paper the transient voltage distribution in the excitation winding of a salient pole synchronous generator is simulated by solving the problem entirely in the frequency domain, i.e., without any use of the traditional ordinary differential equations solvers. Thismakesit possible to tune the parameters of a simplified electric model to the frequency response of the studied winding. It is shown that for highly inductive windings a single transmission line model with frequency dependent parameters can reproduce voltage transients very accurately, in a broad interval of frequency, relevant for power electronics and electromagnetic compatibility applications. Furthermore, the paper presents the experimental setup which has been needed for generating the fast varying voltage edges.

  • 6.
    Hedlund, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Doktorand, Uppsala Universitet.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eddy Currents in a Passive Magnetic Axial Thrust Bearing for a Flywheel Energy Storage System2017In: International journal of applied electromagnetics and mechanics, ISSN 1383-5416, E-ISSN 1875-8800, Vol. 54, no 3, p. 389-404Article in journal (Refereed)
    Abstract [en]

    Two types of passive magnetic lift bearings were evaluated in terms of thrust force and eddy current losses. The first type of bearings were based on two sets of segmented Halbach arrays mounted in repulsive mode, and the second type was based on ring-magnets. The eddy-currents studied arose in the bearing due to manufacturing variations of magnetic remanence, and due to non-radial magnetization. Both a 3D time-dependent and a quasi-stationary Finite-Element Method (FEM) formulation were used, and the simulated results were compared with lift-force measurements from experiment. The losses were found (by FEM) to be in the order of 25 W at a rotational speed of 30000 rpm while lifting a 45 kg rotor with a stiffness of 359 N/mm.

  • 7.
    Hedlund, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Passive Axial Thrust Bearing for a Flywheel Energy Storage System2013Conference paper (Refereed)
  • 8.
    Kristiansen Nøland, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Univ Coll Southeast Norway, Fac Technol Nat Sci & Maritime Sci, N-3184 Borre, Norway.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Comparison of Thyristor Rectifier Configurations for a Six-Phase Rotating Brushless Outer Pole PM Exciter2018In: IEEE Transactions on Industrial Electronics, ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, no 2, p. 968-976Article in journal (Refereed)
    Abstract [en]

    Recent technological developments have caused a renewed interest in the brushless excitation system. With the application of wireless communication, the conventional diode bridge has been replaced with fully controllable thyristors on the shaft. It offers the same dynamic performance as the conventional static excitation system. The thyristor bridge of the conventional three-phase exciter needs to be controlled with a high firing angle in normal operation in order to fulfill a requirement of both a high ceiling voltage and a high ceiling current. A high firing angle causes high torque ripple to be absorbed by the exciter stator and a low power factor results in a low utilization of the designed exciter. In this contribution, we present a strategy that solves this problem by looking into combinations of thyristor configurations of a double-star six-phase connection of the exciter. Experimental results are used to verify the circuit models implemented for this investigation. A hybrid-mode 12-pulse thyristor bridge configuration seems to be a good solution for implementations in commercial apparatus. An additional switch interconnects two separate thyristor bridges from parallel- to series connection at the rectifier output, and utilizes the advantages of both topologies.

  • 9.
    Lundin, Urban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Pérez, José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Fregelius, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Nøland, Jonas Kristiansen
    NTNU, Norwegian University of Science and Technology.
    Start of a synchronous motor using rotor field polarity inversion and rotor back-emf sensing2020In: 2020 International Conference on Electrical Machines (ICEM), 2020, Vol. 1, p. 338-344Conference paper (Refereed)
    Abstract [en]

    Synchronous motors are hard to line start due to torque pulsations at zero rotor speed and low starting torque when started using induced current in a damper squirrel cage. By inverting the rotor pole polarity at appropriate times it is possible to, in principle, achieve uniform torque, albeit pulsating with twice the line frequency at zero initial rotor speed. This has been demonstrated in an earlier work. In this paper we demonstrate that high torque starting using the back-emf in the field winding as triggering signal for the rotor polarity inversion is possible. We further discuss the origin of the rotational energy and active and reactive power pulsations. Finally, we show that it is possible to operate a synchronous motors at continuous asynchronous speed by inverting the polarity of the rotor current and adjusting the field current accordingly, although down rated.

  • 10.
    Nøland, Jonas Kristiansen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, J. José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator2017In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 53, no 3, p. 2016-2027Article in journal (Refereed)
    Abstract [en]

    Generally, PM machines are used as PMG pre-exciters in 3-stage brushless excitations systems. This paperpresents the design, characterization and prototyping of a rotatingbrushless PM exciter used in a proposed 2-stage excitation systemfor a synchronous generator. The proposed design reduces thenumber of components compared with conventional systems.A comparison with the state-of-the-art conventional excitationsystems is given. The design of a fast-response, or high initialresponse, brushless exciter requires active rectification on therotating frame, replacing the non-controllable diode bridge. Theobjective was to construct an exciter with the capability of a50 Aoutput field current as well as a high value of the available ceilingvoltage and ceiling current. The final exciter was constructed to befitted into an in-house synchronous generator test setup. A finiteelement model of the exciter was validated with experimentalmeasurements. The exciter prototype is also compared with analternative armature design with non-overlapping single-layerconcentrated windings but with the same main dimensions.The paper includes a general design procedure suitable foroptimization of PM brushless exciters that fulfill the requirementsof their synchronous generators and the grid.

  • 11.
    Nøland, Jonas Kristiansen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Univ Coll Southeast Norway, Fac Technol & Maritime Sci, N-3184 Borre, Norway.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesus José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup2016In: Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup / [ed] IEEE Xplore, 2016, p. 259-265Conference paper (Refereed)
    Abstract [en]

    This paper deals with the characterization and construction of a rotating brushless PM exciter intended for synchronous generator excitation purposes. Traditionally, PM exciters are used as pre-exciters in synchronous generator excitations systems. In order to reduce the number of components and to increase the step time response of the system, a PM exciter is designed as an outer pole PM machine, with permanent magnets on the stator and armature windings on the rotor. The exciter was constructed electrically and mechanically to be fitted into an in-house synchronous generator test setup. A finite element model of the exciter was validated with no-load measurements of voltages and magnetic flux densities. The exciter was then characterized with unsaturated and saturated parameters.

  • 12.
    Nøland, Jonas Kristiansen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Univ Coll Southeast Norway, Dept Engn, Fac Technol & Maritime Sci, N-3184 Borre, Norway.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter2016In: Proceedings Of The IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, IEEE, 2016, p. 1924-1929Conference paper (Refereed)
    Abstract [en]

    his paper investigates the performance of different power electronic interfaces for a rotating brushless permanent magnet exciter, designed for a synchronous generator test setup. A passive rotating diode bridge is commonly used as the rotating interface on conventional brushless excitation systems. Those systems are known to be slow dynamically, since they cannot control the generator field voltage directly. Including active switching components on the rotating shaft, like thyristors or transistors, brushless excitation systems can be comparable to static excitation systems. Brushless excitation systems has the benefit of less regular maintenance. With permanent magnets on the stator of the designed exciter, the excitation system improves its field forcing capability. Results show that modern power electronic interfaces utilize the exciter machine optimally, increase the power factor, reduce the torque pulsations, maintain the available field winding ceiling voltage and improve the field winding controllability.

  • 13.
    Nøland, Jonas Kristiansen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Univ Coll Southeast Norway, Fac Technol Nat Sci & Maritime Sci, N-3184 Borre, Norway.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter2018In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 33, no 1, p. 59-67Article in journal (Refereed)
    Abstract [en]

    The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this paper, a six-phase outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A fast-response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents possible, improving the transient behavior of the synchronous generator. In this paper we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage and reduce the steady state torque ripple. Experimental results are given for validating the models implemented for the analysis.

  • 14.
    Perez-Loya, J. Jose
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Initial Performance Tests of a Permanent Magnet Thrust Bearing for a Hydropower Synchronous Generator Test-Rig2016Conference paper (Refereed)
  • 15.
    Perez-Loya, J. Jose
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Optimization of Force Between Cylindrical Permanent Magnets2014In: IEEE Magnetics Letters, ISSN 1949-307X, E-ISSN 1949-3088, Vol. 5, p. 0800404-Article in journal (Refereed)
    Abstract [en]

    We calculated analytically and with the finite-element method the force between two identical coaxial cylindrical magnets for nine different magnetic materials at separations of 1, 3, 5, 7, and 9 mm and for height-to-diameter ratios between 0.1 and 2. For the analytical calculations, we assumed homogeneous magnetization. For the nonhomogeneous case, we used the finite-element method taking into consideration the magnetic flux density vs. field (B-H) curves of the materials. The results show that, similarly for cuboid magnets, the maximum force for a given volume of permanent-magnet material was achieved for a height-to-diameter ratio around 0.4 for homogeneously magnetized (ideal) permanent magnets. We also show that this is not always true for the nonhomogeneous cases. The resulting forces are dependent on the B-H curve of the magnets. As the B-H curves of the materials deviate from their ideal counterparts, the aspect ratio that yields maximum force increases.

  • 16.
    Pérez-Loya, J. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Analysis and control of magnetic forces in synchronous machines2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In a synchronous machine, radial, tangential, and axial forces are generated. In this thesis, three different technologies to control them are proposed. The first one, involves the utilization of the radial forces that arise between the rotor and the stator. This is achieved by segmenting the rotor field winding into groups of poles and controlling their corresponding magnetization individually. This technology is particularly useful to achieve magnetic balance and to create controllable radial forces. The second technology, involves the control of the rotor field in order to influence the tangential forces that produce torque. This is achieved by inverting the rotor field winding polarity with respect to the stator field. With this technique, breaking and accelerating torques can be created. It is particularly useful to start a synchronous machine. Finally, the application of axial forces with a magnetic thrust bearing is discussed. The main benefits of this technology are higher efficiency and increased reliability.

    The work presented in this thesis was carried out within the Division of Electricity in the Department of Engineering Sciences at Uppsala University. It is based on original research supported by analytical calculations, computational simulations and extensive experimental work.

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  • 17.
    Pérez-Loya, J. J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. J. D.
    Lundin, U.
    Arrangement and method for force compensation in electrical machines2016Patent (Other (popular science, discussion, etc.))
  • 18.
    Pérez-Loya, J. J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. J. D.
    Lundin, U.
    Arrangement for supporting a rotatable body2016Patent (Other (popular science, discussion, etc.))
  • 19.
    Pérez-Loya, J. J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. J. D.
    Lundin, U.
    Fail-safe system for discharging a magnetic thrust bearing2016Patent (Other (popular science, discussion, etc.))
  • 20.
    Pérez-Loya, J. Jose
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. Johan. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Demonstration of active compensation of unbalanced magnetic pull in synchronous machines2017In: CIGRE Science & Engineering, Vol. 8, p. 98-107Article in journal (Refereed)
  • 21.
    Pérez-Loya, J. Jose
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. Johan. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Synchronous machine and method for operating a synchronous machine2017Patent (Other (popular science, discussion, etc.))
  • 22.
    Pérez-Loya, J. Jose
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Magnetic thrust bearing for a hydropower unit with a Kaplan turbine2017Manuscript (preprint) (Other academic)
  • 23.
    Pérez-Loya, J. José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, C. Johan D.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Demonstration of Synchronous Motor Start by Rotor Polarity Inversion2018In: IEEE Transactions on Industrial Electronics, ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, no 10, p. 8271-8273Article in journal (Refereed)
    Abstract [en]

    Synchronous motors are reliable and efficient, but it is relatively difficult to start them. In some cases, a variable frequency drive is utilized. In some other, asynchronous start is achieved by virtue of induced currents in a solid rotor, or a rotor damper cage installed for this purpose. In this contribution, a method to start a synchronous machine without a damper cage is presented. The starting was achieved by inverting the polarity of the rotor field winding in a timely manner with respect to the rotating stator field. The technique was verified with experiments performed on a 200 kVA experimental test rig and also simulated on a 20 MVA machine.

  • 24.
    Pérez-Loya, J. José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Abrahamsson, C. Johan D.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Electromagnetic losses in synchronous machines during active compensation of unbalanced magnetic pull2019In: IEEE Transactions on Industrial Electronics, ISSN 0278-0046, E-ISSN 1557-9948, Vol. 66, no 1, p. 124-131Article in journal (Refereed)
    Abstract [en]

    Unbalanced magnetic pull (UMP) is typically caused by rotor or stator shape defects, electrical short circuits, eccentric rotor/stator bores, as well as unreasonable pole-slot combinations. It leads to vibration and increases noise and energy losses of the machine. By actively controlling the magnetic fields and forces that arise between the rotor and stator by regulating the rotor field current of separated pole groups, it is possible to cancel it. In this paper, we measure and calculate the currents induced in the damper bars for a synchronous machine test rig under 20% static eccentricity with and without active compensation of UMP. This is done to validate our finite-element calculations. Afterward, we perform loss calculations for a 74-MVA synchronous generator with and without stator parallel circuits. We find that, with active compensation of UMP for an eccentric machine, the damper bar currents and stator parallel circuit circulating currents can be eliminated and the electromagnetic efficiency of the machine that has a static eccentricity fault increases.

  • 25.
    Pérez-Loya, J. José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Simple Method to Calculate the Force between Thin Walled Solenoids2016In: Progress In Electromagnetics Research M, ISSN 1937-8726, Vol. 51, p. 93-100Article in journal (Refereed)
    Abstract [en]

    We developed a simple method to calculate the axial force between concentric thin walled solenoids. To achieve this, the force between them was mapped as a function of their geometrical relations based on separation-to-diameter ratios. This resulted in an equation and a set of data. We used them together to calculate axial forces between two coaxial thin walled solenoids. With this method, direct evaluation of elliptical integrals was circumvented, and the forces were obtained with a simple expression. The results were validated against solutions obtained with an existing semi-analytical method and force measurements between high coercivity permanent magnets.

  • 26.
    Pérez-Loya, Jesus José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    de Santiago, Juan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Construction of a Permanent Magnet Thrust Bearing for a Hydropower Generator Test Setup2013Conference paper (Refereed)
  • 27.
    Pérez-Loya, Jesus José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Rodriguez, E.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Stephan, R. M.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Magnetic Modeling and Measurement of Forces Between Permanent Magnet Rings used as Passive Magnetic Bearings2013Conference paper (Refereed)
  • 28.
    Pérez-Loya, Jesús José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Performance tests of a permanent magnet thrust bearing for a hydropower synchronous generator test-rig2017In: ACES Journal, Vol. 32, no 8, p. 704-711Article in journal (Refereed)
    Abstract [en]

    Permanent magnets are an attractive material to be utilized in thrust bearings as they offer relatively low losses. If utilized properly, they have a long service lifetime and are virtually maintenance free. In this contribution, we communicate the results of the tests performed on a permanent magnet thrust bearing that was custom built and installed in a hydropower synchronous generator test-rig. Tridimensional finite element simulations were performed and compared with measurements of axial force. Spin down times and axial force ripple have also been measured. We found good correspondence between the measurements and the simulations.

  • 29. Rodriguez, Elkin
    et al.
    Pérez-Loya, Jesus José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Santiago, Juan de
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Costa, Felipe S
    Sotelo, Guilherme G
    Goncalves de Oliveira, Janaina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Stephan, R. M.
    Passive Magnetic Bearing System2014Conference paper (Refereed)
  • 30. Rodriguez, Elkin
    et al.
    Santiago, Juan de
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesus José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Costa, Felipe S
    Sotelo, Guilherme G
    Goncalves de Oliveira, Janaina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Stephan, Richard M
    Analysis of passive magnetic bearings for kinetic energy storage systems2014Conference paper (Refereed)
  • 31.
    Sahoo, Subrat
    et al.
    ABB Corp Res, Västerås, Sweden..
    Holmgren, Fredrik
    Contec Control Technol AB, Arboga, Sweden..
    Rodriguez, Pedro
    ABB Corp Res, Västerås, Sweden..
    Pérez, José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
    Damper Winding Fault Analysis in Synchronous Machines2018In: 2018 XIII international conference on electrical machines (ICEM), IEEE, 2018, p. 1789-1795Conference paper (Refereed)
    Abstract [en]

    A Damper winding performs an important function of protecting the Synchronous Motors (SMs) during transient operations. They also happen to be one source of concern for failure of SMs, which are otherwise quite reliable. The situation aggravates when the motors are fed by variable frequency drives, which brings additional stress on the damper bars. This paper presents theoretical simulations of a salient pole SM with twelve poles, containing three damper bars in each pole, during healthy as well faulty damper bar conditions. The current distribution is calculated in each damper bar. Experiments were conducted on the same SM and the current in the damper bars as well inter-connecting poles were measured and captured on a rotating wireless communication platform, both during healthy and faulty conditions of the damper bars with varying severity. The fault indicators are presented to detect damper bar failure conditions, thereby helping preventive maintenance of SMs.

1 - 31 of 31
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