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  • 1. Austrin, L.
    et al.
    Torabzadeh Tari, Mohsen
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Larsson, A.
    Analysis of a feasible pulsed-power supply system for an Unmanned Aerial Vehicle2006In: ICAS-Secretariat, 2006, p. 3605-3612Conference paper (Refereed)
    Abstract [en]

    More Electric Aircraft technology enables the power supply of electric energy weapons such as high-power microwave and laser weapons. Aspects of electric power generation, energy storage, distribution and pulse-conditioning systems for the power supply of directed energy weapons in Unmanned Aerial Vehicle are addressed in this paper. A trend in aircraft design is to electrify more parts of the aircraft via the concept of More Electric Aircraft (MEA) and its technology which allows for increased electric power consumption. Thus, MEA technology enables the power supply of weapons and protection systems that are using electric energy. Among these devices directed energy weapons such as high-power microwave (HPM) and laser weapons are feasible. Such systems require high power pulsed electric energy with, thus imposing new requirements of on-board power supplies. In the demonstrated concept it is important to analyze power losses and efficiency as well as weight and volume in order to evaluate the possibility to adapt the system in an UAV.

  • 2. Austrin, Lars
    et al.
    Torabzadeh-Tari, Mohsen
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A new high power density generation system2006In: ICAS-Secretariat, 25th Congress of the International Council of the Aeronautical Sciences 2006, 2006, p. 3600-3604Conference paper (Refereed)
    Abstract [en]

    A trend of increased Electric Power in Aircraft stresses the need of robust, low weight systems with low losses. New hard and soft magnetic materials have made it feasible to work with high speed and high frequency. Applications of new soft magnetic materials and hard magnetic materials like NeFeB magnets have enabled high density power generation systems. A new concept comprising a high speed PM-generator system and a magnetic amplifier control is presented. Magnetic amplifiers are used in the power supply of the Electronic Flight Control System in the Swedish "Gripen" fighter-aircraft. This technology is attractive in More Electric Aircraft (MEA) systems due to the possibility to achieve a compact, robust and a highly reliable system with low losses. Applications of new soft magnetic materials, such as amorphous magnetic alloys, have enabled the use of magnetic amplifier (magamp) technology in the design of competitive electric power converters. This paper presents a studied design on a 20-40 kW generator system including a +/- 270V controlled output, performed by magnetic amplifier technology. This work addresses the power generator, and the power converter. High speed PM-generators are offering high power density. The impact of operating a generation system with higher frequency and an increasing number of poles as well as the advantages with new soft magnetic materials is studied. The iron losses and the copper losses are analyzed for the generator, and the power converter.

  • 3.
    Torabzadeh-Tari, Mohsen
    KTH, School of Electrical Engineering (EES).
    Analysis of Electro-Meachanical Actuator Systems in More Electric Aircraft Applications2005Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Conventional hydraulic actuators in aircraft are demanding regarding maintenance which implies high operation costs. In recent years the focus therefore has been set on electro-hydrostatic and electro-mechanical actuators.

    The aim of this work is to analyze and evaluate the possibility of introducing electro-mechanical actuators (EMAs) in more electric aircraft applications. The major goal is to optimize the weight of such actuator systems including the electro-machine (electric motor) gear mechanism and power converter, without loss of reliability. Other optimisation criteria on such solutions are low losses and good thermal properties.

    A quasi-static model approach of EMAs is used here in order to decrease the simulation time. It is possible because the low (mechanical) and high (electrical) frequency components are separated in the model, see [1]. The inverters and converters are described as fictive DC-DC transformers with corresponding efficiencies, see [2]. By introducing an object oriented approach the model is flexible and re-usable and can be used as a framework in the future build-up of models of entire MEA aircrafts, see [3].

    Power density, cost and weight of the actuator systems are some of the important key factors for comparing purpose and as a platform for the dimensioning of the aircraft. The next issue becomes the scalability of the model and the key factors, because of the diversity of the actuators used in different parts of the MEA aircraft. Therefore the ambition is set to build up a database of different scalable actuator solutions which among others returns these key factors as output.

  • 4.
    Torabzadeh-Tari, Mohsen
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dimensioning Tools of MEA Actuator Systems, Including Modeling, Analysis and Technology Comparison2008Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    Aircraft design is an example of complex engineering where dimensioning tools can be valuable for the designers and decision makers in the early stage of the development process. These tools can be in form of a database over key numbers for different components or technologies.

    One of the critical parts of an aircraft is the actuator system. Conventional hydraulic actuators are demanding regarding maintenance which implies high operation costs. Therefore in recent years the focus has been set on electro-hydrostatic and electro-mechanical actuators.

    The aim of this work is to build a platform which can make it easier for designers and decision makers to analyze, compare and optimize different technologies regarding the actuator system.

    For this reason a simplified quasi-static actuator model, including reactive power consumption has been developed. This model makes it possible to reduce the complexity of the actuator models to such extent that the resulting computional tool can be used for studies of the system performance during entire flight missions and/or for optimization. Power density, cost and weight of the actuator systems are some of the important key numbers for comparing purpose and as a platform for the dimensioning of the aircraft. The ambition is then to build up a database of different actuator solutions with the key technical parameters mentioned above, that can be used in modeling and dimensioning of an aircraft.

    In order to avoid time consuming finite element calculations when analyzing an electrical machine a reluctance network model can be used. The basic idea of the proposed network model is to divide the rotor and the stator into a grid of small reluctance elements and provide those that correspond to the permanent magnet and the air gap between the magnets with time varying reluctances. The suggested computationally approach constitute a fast way to evaluate permanent magnet electrical machines with the respect to their performance.

    A preferred electrical machine provided with balance teeth and concentrated windings showed good electromechanical and thermal behavior. A balance tooth is a tooth without winding between each adjacent phases that has a cooling effect on the nearest windings, resulting in less copper losses. The balance teeth increases the voltage-time area, leading to higher induced voltage and higher torque production. Another advantage of the chosen design is its redundancy and fault tolerance capabilities. The machine comprises two independent half machines that also offers a high level of redundancy with two separate power channels.

  • 5. Torabzadeh-Tari, Mohsen
    et al.
    Austrin, Lars
    Larsen, Martin
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Optimization and characterization by finite element method of an electromechanical actuator for more electric aircraft applications2006In: Proceedings for Actuator 2004 conference, 2006Conference paper (Refereed)
    Abstract [en]

    The future More Electric Aircraft (MEA) technology focus on increasing the use of electrical equipment to a larger extent, e.g. replacing conventional hydraulic and pneumatic actuators with electromechanical or electro hydrostatic actuators to reduce weight, cost and maintenance. Advances in enabling technologies of electric power generation, distribution, and utility equipment have made the use of electric actuators more competitive. Electric actuation can be based on Electro Hydrostatic (EHA), ElectroMechanical (EMA), or Magnetostrictive Actuator (MA) concepts. In this paper the experiences from a performed electromechanical actuator demonstrator program are presented together with a motor optimization method intended for future programs. The desccribed actuator demonstrator is designed for an Unmanned Aerial Vehicle (UAV) application. The important key design criteria?s for the demonstrator have been reliability, redundancy, torque density, and reduced maintenance.

  • 6.
    Torabzadeh-Tari, Mohsen
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Austrin, Lars
    Tidblad-Lundmark, Sonja
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Simulation and analysis of a new high power density generator2006In: ICAS-Secretariat - 25th Congress of the International Council of the Aeronautical Sciences 2006, Curran Associates, Inc., 2006, Vol. 5, p. 3332-3337Conference paper (Refereed)
    Abstract [en]

    When high power electrical machines are required, an increase in the mechanical frequency and/or number of poles is suggested. The analyzed electrical machine produces a high torque density due to a concentrated winding arrangement, in combination with the increased width of the stator teeth. It is a permanent magnet synchronous generator, [1] and is intended for operation at high speed and high power applications. The large cross-sectional area of the magnetic core flux paths is one of the reasons of the generators good performance. In this paper the impact on output power and losses by increasing number of poles and generated input speed is treated. New soft magnetic material also is addressed. The feasibility of using key parameters of the involved electrical machine, estimated by FEM-analyses and condensed into a quasi-static model, [2] is also addressed in this paper. These extracted parameters constitute a platform for a scaleable model.

  • 7.
    Torabzadeh-Tari, Mohsen
    et al.
    KTH, School of Electrical Engineering (EES).
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A PORTABLE IMPLEMENTATION OF A MODEL OF ELECTROMECHANICAL ACTUATORS USED IN MORE ELECTRIC AIRCRAFT DIMENSIONING TOOLS2004In: Proceedings of Actuator 2004, 2004Conference paper (Refereed)
    Abstract [en]

    Modelling of the electric power systems of a More Electric Aircraft (MEA) is multidisciplinary and quite CPU demanding. This paper suggests a modelling approach of the electromechanical actuators implemented in a portable code constituting a reasonable compromise between required CPU-time and accuracy. The approach is to divvide the actuator model in three partitions, namely an current control rectifier, electromachine and gear model. By using only quasi-stationary electrical state variables [1] the variations within the electrical power cycles are neglected. The involved electromachines are modelled in terms of their efficiencies, moment of inertia, torque and back EMF constants. The rectifiers are desccribed in terms of equivalent load dependent loss resistances corresponding to their efficiencies [2,3]. The gears are desccribed in terms of efficiencies and gear ratios. The model is designed in the modelling language Modelica with the objective that the model, i.e. the implementation of the model, should be flexible, extensible, portable to MATLAB and object oriented. The proposed modelling approach is considered to constitute a framework in future build-up of models of entire MEA aircrafts [4].

  • 8.
    Torabzadeh-Tari, Mohsen
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Engdahl, Göran
    KTH, Superseded Departments, Electrical Systems.
    A quasi-static modelling approach of electromechanical actuators2004In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 272, p. E1705-E1707Article in journal (Refereed)
    Abstract [en]

    This paper presents a suggested modelling approach of an electromechanical actuator, where the performance of involved semiconductor devices and tentative motors as PM, transversal, torus, and switched reluctance electrical machines are condensed into look-up tables. Current and voltages are then desccribed in form of quasi-static rms values quantities, and the actuator mechanical outputs in momentary forces and velocities. The proposed modelling approach is considered to be one ingredient in future build-up of models of entire MEA aircrafts.

  • 9.
    Torabzadeh-Tari, Mohsen
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Time Domain Frequency Separation, TDFS-Model Approach Including Reactive Power of a Novel Electromechanical Actuator for MEA Applications2008In: ACTUATOR 08, CONFERENCE PROCEEDINGS / [ed] Borgmann H, 2008, p. 945-948Conference paper (Refereed)
    Abstract [en]

    Future More Electric Aircraft (MEA) technology focuses on increasing the use of electrical equipment to a larger extent, e.g. replacing conventional hydraulic and pneumatic actuators with more electric components to reduce weight, cost and maintenance. Advances in enabling technologies of electric power generation, distribution, and consumption have made the use of electric actuators more competitive. Electric actuation can be based on Electro Hydrostatic (EHA), Electro Mechanical (EMA), or Magnetostrictive Actuator (MA) concepts. The governing idea in the TDFS model approach is to separate the high (electrical) and low (mechanical) frequency parts of the model and thereafter only consider the low frequency part. Electrical components as current and/or voltage converters/inverters are then described in terms of RMS-vales of currents and voltages and efficiencies or in circuit diagrams in form of load dependent resistors and in electromachines by means of load dependent loss resistances equivalent with their electromechanical efficiencies. Step-down and step-up voltage converters are described as fictive DC/DC transformers. The reactive power drawn by the motor is accounted for by a parallel electrical branch comprising a Current sink. This approach makes it possible to reduce the complexity of power system models of tentative systems to such extent that the resulting computational tool easily can be used for studies of the whole system performance during entire flight missions and/or for optimization. The electrical machine of the studied actuator is a permanent magnet synchronous machine intended for operation at relatively low speed and high torque. The continuous output power is 1 [kW] with a voltage level of 270 VDC at the DC-bus. This machine shows promising performance for more electric aircraft applications. The modeling approach in this paper shows that it is possible to perform simulations on entire flight missions. This feature constitutes a valuable tool for decision making, when different technologies are to be compared. The use of described actuator model is illustrated for an Unmanned Airborne Vehicle (UAV) application.

  • 10. Torabzadeh-Tari, Mohsen
    et al.
    Engdahl, Göran
    Austrin, Lars
    Krah, Julius
    A QUASI-STATIC MODELLING APPROACH OF AIRBORNE POWER SYSTEMS2003In: Proc. NaCoMM 2003, 2003Conference paper (Refereed)
    Abstract [en]

    Modelling the whole power system of an airborne system requires very high computational capacity. This paper presents a possible approach to overcome this obstacle when considering new technology and topologies in airborne systems. Using controlled current converters and electromechanical actuators for rudder control are examples of such new technology. The governing idea is to separate the high (electrical) and low (mechanical) frequency parts [1] of the model and thereafter only consider the low frequency part. Electrical components as current and/or voltage converters/inverters are then desccribed in terms of efficiencies or in circuit diagrams in form of load dependent resistors [2] and in electromachines by means of load dependent loss resistances equivalent with their electromechanical efficiencies [3]. Step-down and step-up voltage converters are desccribed as fictive DC/DC transformers. This approach makes it possible to reduce the complexity of power system models of tentative systems to such extent that the resulting computational tool can be used for studies of the system performance during entire flight missions and/or for optimisation.

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