L. Alberti

Libera Università di Bozen-Bolzano, Bozen, Trentino-Alto Adige, Italy

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Publications (45)39.04 Total impact

  • N. Bianchi, O. Bottesi, L. Alberti
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    ABSTRACT: There is a growing interest in adopting electrical motors exhibiting high efficiency. Therefore, induction machines are often replaced by more efficient electrical drive solutions. Variable-speed drives are often chosen instead of the traditional grid-connected solutions, so as to avoid unefficient regulations at constant speed, when the machine operates at part load. This paper aims to compare different types of electric motor drives for high efficiency applications: an induction motor drive, a synchronous reluctance motor drive, and a permanent magnet assisted synchronous reluctance motor drive. The innovative field-oriented analysis technique is applied to estimate the motor drive performance. This method of analysis is particularly advantageous in comparing the induction motor performance to those of synchronous machines. The comparison among the capabilities of the three electric drives is carried out combining both analytical and finite element methods. The analysis strategy adopted has been arranged so as to obtain rapidly the motor drive capability.
    Ecological Vehicles and Renewable Energies (EVER), 2013 8th International Conference and Exhibition on; 01/2013
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    ABSTRACT: This paper focuses on the selection of a fractional-slot winding for permanent-magnet (PM) machines. The choice of the proper combination of the number of slots and number of poles, together with the corresponding winding layout, has a strong impact on the PM machine performance, in terms of torque density, torque ripple, magnetomotive force harmonic content, and induced rotor losses, as well as the capability to limit the short-circuit current and other fault-tolerance features. Considering these characteristics, this paper aims to help the PM machine designer to select the proper winding configuration, giving useful indications. The winding choice criteria are given using analytical equations, so that their implementation is easy. In this way, the collection of such criteria becomes a helpful tool in the design process.
    IEEE Transactions on Industry Applications 01/2013; 49(3):1316-1324. · 1.67 Impact Factor
  • L. Alberti, N. Bianchi, S. Bolognani
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    ABSTRACT: The variation of the self-sensing capability of different type of electrical machines due to parasitic effects is considered in this papers. Thanks to a specific simulation strategy the variations of the machine saliency and the error angle are computed considering different rotor positions and different working points. It is shown that a large variation occurs in particular working points. The presented approach is useful during the design process of the machine in order to assess the self-sensing capability of the machine and its impact on the control scheme adopted in the drive.
    Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE; 01/2013
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    ABSTRACT: This paper describes a thermal model for a duplex three-phase induction machine for fault-tolerant applications. The three- and six-phase variations of the duplex three-phase machine operation under fault conditions are considered. Different winding configurations are investigated. Thermal analysis is performed using analytical and finite-element models. An experimental validation is presented for load operating conditions.
    IEEE Transactions on Industry Applications 01/2013; 49(4):1523-1530. · 1.67 Impact Factor
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    ABSTRACT: An analysis of the magnetic behavior of different slot geometries is proposed by means of finite element (FE) software. An intentionally created anisotropy is introduced in the rotor bar geometry, so as to allows a sensorless detection of the IM rotor position. The proposed FE procedure allows to evaluate the sensorless control capability of the IM. The parameters of the induction motor (IM) are determined by means of a FE procedure, based on the d- and q- axis model of the machine. Such a procedure is quite rapid, since is based on the time harmonic response to a high frequency injected signal in the stator winding. This procedure is used to predict the variation of the IM parameters and it results to be useful for both analysis of the IM performance and the design step of the machine. A rotor geometry with an intentionally created magnetic saliency have been analyzed. The rotor prototype is under construction, in order to verify the predicted results.
    Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE; 01/2013
  • L. Alberti, N. Bianchi, S. Bolognani
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    ABSTRACT: The self-sensing capability of an inset permanent magnet machine is investigated in this paper. Thanks to a specific simulation strategy, the variations of the machine saliency and the error angle are computed considering different rotor positions and different loading conditions. Parasitic effects as saturation and eddy currents in both permanent magnets and lamination are also included in the analysis. The approach here presented is useful during the design process of the machine in order to assess the self-sensing capability of the machine and its impact on the drive control scheme.
    Sensorless Control for Electrical Drives and Predictive Control of Electrical Drives and Power Electronics (SLED/PRECEDE), 2013 IEEE International Symposium on; 01/2013
  • A. Fasolo, L. Alberti, N. Bianchi
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    ABSTRACT: Switching Flux Permanent Magnet machines compared with Interior Permanent Magnet machines are presented to be interesting solutions in terms of torque per volume density, compactness, active material layout and cooling capability. The flux linkage results to be bi-directional and voltage is almost sinusoidal. These machines are then interesting for AC drives and field weakening operation. Employing low cost magnet material must be carefully evaluated despite of the lack of torque capability adopting rare earths permanent magnet can be recovered with cost saving.
    Electrical Machines (ICEM), 2012 XXth International Conference on; 01/2012
  • L. Alberti, N. Bianchi
    Energy Conversion Congress and Exposition (ECCE), 2012 IEEE; 01/2012
  • L. Alberti, M. Barcaro, N. Bianchi
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    ABSTRACT: Among the Permanent Magnet (PM) machines, the Interior PM (IPM) machine is proposed, despite of a strong non linear behaviour and a complex design, as a good candidate thanks to its interesting peculiarities, i.e., higher torque in flux-weakening operation, higher fault-tolerance, and ability to adopt low cost PMs. A second trend in designing PM machines concerns the adoption of fractional-slot (FS) non-overlapped coil windings, which reduce the end winding length and consequently the Joule losses and the cost. Therefore, the adoption of IPM machine with a FS winding aims to combine both advantages: high torque and efficiency in a wide operating region. However, the combination of an anisotropic rotor and a FS winding stator causes some problems. The interaction of the MMF harmonics due to the stator current interact with the rotor anisotropy causing a very high torque ripple. This paper illustrates a procedure to design an IPM motor with FS winding exhibiting a low torque ripple. The design strategy is based on two consecutive steps: at first, the winding is optimized by taking a multi-layer structure, then the rotor geometry is optimized by adopting a non-symmetric structure. As an example, a 12-slot 10-pole IPM machine is considered, achieving a torque ripple lower than 1.5% at full load.
    Energy Conversion Congress and Exposition (ECCE), 2012 IEEE; 01/2012
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    ABSTRACT: This paper presents a novel strategy to compute the high-frequency signal injection response of an electrical machine adopted in a sensorless electric drive. Thanks to the proposed strategy the self-sensing capability of the machine can be evaluated during the design process. A small-signal model of the machine in the d-q reference frame is derived and adopted to perform suitable finite-element (FE) simulation to compute the machine parameters at the injection frequency. The proposed procedure is validated by the comparison with other simulation strategies as well as with experimental results.
    Electrical Machines (ICEM), 2012 XXth International Conference on; 01/2012
  • Luigi Alberti, Nicola Bianchi
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    ABSTRACT: This paper describes a set of experimental tests on a dual three-phase induction machine for fault-tolerant applications. Both three-phase and six-phase machine operations are considered. Different winding configurations are investigated and compared in case of both open-circuit and short-circuit faults. Experimental tests for each configuration are reported at no-load and under load operating conditions.
    IEEE Transactions on Industrial Electronics 01/2012; 59(5):2041-2048. · 6.50 Impact Factor
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    ABSTRACT: A novel strategy is presented to compute the high-frequency signal injection response of a ringed-pole electrical machine. The self-sensing capability of the machine is evaluated by means of a small-signal model of the machine in the d-q reference frame and finite-element simulations. The proposed procedure is validated by the comparison with other simulation strategies and experimental results.
    Sensorless Control for Electrical Drives (SLED), 2012 IEEE Symposium on; 01/2012
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    ABSTRACT: Purpose – The purpose of this paper is to investigate the impact of control strategy selection on the power performance of wave energy converters for different ratings of the Power Take-Off (PTO) system. Design/methodology/approach – The case of a point absorber equipped with an all-electric PTO is considered. The effect of control techniques and electrical generator design is analyzed from a theoretical standpoint and then veri?ed through integrated hydrodynamic-electric simulations. Findings – It has been proved that control parameters that maximize the power extraction from the waves can be derived based on the power and torque constraints imposed by the electrical machine. Originality/value – An optimized and integrated approach to the control strategy selection and generator design for point absorbers has been presented, which maximizes the electric power generation from sea waves under real conditions and represents a good trade-off for the PTO from both the technical and the economic standpoint.
    COMPEL International Journal of Computations and Mathematics in Electrical 01/2012; 32(1):233-247. · 0.28 Impact Factor
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    ABSTRACT: A challenge during the design process of an electrical machine is the characterization of the various parameters in a computational time as short as possible. To this purpose, the analysis strategies are manifold. In addition, it is more frequent to obtain parameters of the electrical machine that are necessary for the drive control. In this paper, a strategy to compute the high-frequency signal injection response of an electrical machine adopted in a sensorless electric drive is presented. It allows to determine the self-sensing capability of the machine directly during the design process. Such a capability is defined in any given operating points (for instance along the maximum torque per Amps trajectory). In addition, the computational time required to get such data is very short. After a magnetostatic field analysis, carried out so as to get the torque for a given current, the flux density distribution is stored and the differential reluctivity is evaluated in each element of the mesh. Then, a time-harmonic analysis is carried out in a linearized structure so as to compute the d-q parameters at the injection frequency. The proposed procedure is applied to different type of machines and validated by comparison with experimental results.
    Energy Conversion Congress and Exposition (ECCE), 2012 IEEE; 01/2012
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    ABSTRACT: Purpose – To purpose of this paper is to introduce a procedure to compute the d- and q-axis parameters of the induction motor. Design/methodology/approach – A finite element procedure, based on the d- and q-axis model of the induction motor is adopted. Findings – Such a procedure is well suited to analyse IM with anisotropic rotor, where an intentionally created saliency is introduced in the rotor bar geometry, so as to detect the IM rotor position without sensor. Originality/value – The proposed procedure allows one to evaluate the sensorless control capability of the IM. It will be useful for both analysis of the IM performance and design of the machine itself.
    COMPEL International Journal of Computations and Mathematics in Electrical 12/2011; 31(1):191-205. · 0.28 Impact Factor
  • L. Alberti, N. Bianchi, S. Bolognani
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    ABSTRACT: This paper describes a finite-element (FE) procedure particularly suitable for the prediction of a controlled induction motor (IM) performance. The FE analysis is carried out in the rotor flux reference frame so that only magnetostatic FE simulations are used, reducing the computational time. The use of magnetostatic simulations allows to consider the saturation effects in all the machine parts during all computations. The proposed procedure is suitable for both the analysis and design of IMs, allowing a careful prediction of the drive performance during the various design steps before prototyping. Experimental tests are included in this paper to confirm the accuracy of the predictions achieved by the proposed procedure.
    IEEE Transactions on Industry Applications 05/2011; · 1.67 Impact Factor
  • S.T. Boroujeni, N. Bianchi, L. Alberti
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    ABSTRACT: This paper compares two methods to compute the parameters of a line-start synchronous reluctance (LSSR) machine, by means of finite element analysis. In both methods, both the impact of the skin effect on the rotor parameters and the impact of saturation on magnetizing inductances are taken into account. The first method is based on an equivalent single-phase model of the machine. A pulsating flux is imposed along the d- and q-axes separately, so as to compute the machine parameters along both d- and q-axes. Magnetizing inductances are achieved as a function of the flux, and the rotor resistances and leakage inductances are obtained as a function of rotor frequency. The second method is based on the d-q axis model of the LSSR machine. A rotating magnetic field is imposed, and the d-q axis parameters are estimated simultaneously from the field solution. In addition, such a method allows the cross-saturation to be considered as well.
    IEEE Transactions on Energy Conversion 04/2011; · 2.43 Impact Factor
  • Source
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    ABSTRACT: Purpose - The purpose of the paper is to present a complete design example of an interior permanent magnet integrated starter-alternator (ISA). Design/methodology/approach - After a preliminary design on the basis of an analytical model, finite element simulations are adopted to refine the design of the machine. Findings - The designed ISA drive is able to satisfy all the requirements of modern cars, where the power of the electrical generators is increasing to deliver the on-board power demand. The drive exhibits high torque, driving start, and a wide constant power speed range driving generation. Originality/value - The entire system design is considered in the paper, both the electrical machine and the control strategy.
    COMPEL International Journal of Computations and Mathematics in Electrical 01/2011; 30(1):117-136. · 0.28 Impact Factor
  • Luigi Alberti, Nicola Bianchi
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    ABSTRACT: This paper deals with fractional-slot multilayer windings. They are becoming attractive since they allow reducing the harmonic content of the magnetomotive force. Some examples of such a type of windings are reported in the literature, but they are limited to a few slot/pole combinations. On the contrary, in this paper, a general theory is presented. The main rules for the design of multilayer windings are illustrated. It is also investigated if the adoption of a multilayer winding makes possible the limitation of the torque ripple and the rotor losses of the machine. Several examples and experimental tests are reported to investigate the advantages and the convenience of adopting multilayer windings.
    IEEE Transactions on Industry Applications 01/2011; 49(2). · 1.67 Impact Factor
  • Source
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    ABSTRACT: Starting from 2011, in order to reduce electricity consumption and carbon dioxide emissions, the European MEPS (Minimum Energy Performance Standard) will impose minimum efficiency values for electric motors introduced into the European market. The new European standard requirements will impose non-trivial efforts to manufacturers, in particular for small and medium-sized producers. In this paper, the axial lengthening of the magnetic core is considered as an effective solution to improve the induction motor efficiency class. In fact, this design solution does not require changing stator and rotor laminations, and it can be considered as a "No Tooling Cost" (NTC) solution to improve the rated efficiency. Starting from standard-efficiency total enclosed fan cooled machines, one size has been selected and a "lengthened" motor prototype has been designed and analyzed using a very fast and reliable design procedure based on a coupled analytical-finite element approach. The experimental results confirm the accuracy of the proposed design method and validate the proposed NTC solution to get higher efficiency induction motors. Index Terms—Induction motors, Efficiency measurements, IE efficiency classes, International standards, Finite element method analysis, No Tooling Costs solutions.
    IEEE Transactions on Industry Applications 01/2011; 50(1). · 1.67 Impact Factor

Publication Stats

208 Citations
39.04 Total Impact Points

Institutions

  • 2012
    • Libera Università di Bozen-Bolzano
      Bozen, Trentino-Alto Adige, Italy
  • 2007–2012
    • University of Padova
      • Department of Information Engineering
      Padua, Veneto, Italy
  • 2011
    • Shahrekord University
      Sahr-e Kord, Chahār Maḩāll va Bakhtīārī, Iran
  • 2009
    • Seoul National University
      • School of Computer Science and Engineering
      Seoul, Seoul, South Korea