Publications

  • Computation of Magnetic Forces Using Degenerated Airgap Element,
    Sabin Sathyan, Anouar Belahcen, Juhani Kataja, Francois Henrotte, Abdelkader Benabou, Yvonnick Le Menach,
    IEEE Transactions on Magnetics,
    http://ieeexplore.ieee.org/document/7828131/

    This paper presents an efficient method to calculate the magnetic forces on bodies in contact. The forces are computed through local application of the Virtual Work principle on degenerated airgap elements. The results from this method are compared with those from another software and validated with measurements on a permanent magnet setup. Not only is this technique very accurate, but it also reduces the computational burden related to the problematic meshing of thin layers. The implementation of this method in an open source finite element software having facilities for higher order elements and parallel computation unlocks a cost effective and effectual platform for electromechanical computation of electromechanical devices and magnetic materials.

  • Computation of stator vibration of an induction motor using nodal magnetic forces,
    Sabin Sathyan, Anouar Belahcen, Juhani Kataja, Toomas Vaimann, Jan Sobra,
    2016 XXII International Conference on Electrical Machines (ICEM),
    http://ieeexplore.ieee.org/document/7732827/

    In the case of rotating electrical machines, the magnetic forces acting on the stator teeth are the principal electromagnetic cause of vibrations. Based on this fact, this paper presents a method to compute the vibrations of an induction motor with the aid of magnetic nodal forces. An accurate computation of local or nodal forces is essential in problems pertaining to vibration and noise analysis of electrical machines. Virtual work method is utilized here to compute the nodal forces as the local derivative of magnetic energy from the Finite Element (FE) solution of the magnetic field problem. The magnetic problem is then coupled to an elasticity solver to calculate the displacement due to these forces. The nodal force method is implemented in an open source finite element software Elmer and the entire magneto-mechanical computation is carried out in the same open source tool. The calculated results are then compared to vibration measurements of the motor.

  • 3D Finite Element computation of electromagnetic forces and stress analysis on motor end winding,
    Sabin Sathyan, Anouar Belahcen, Juhani Kataja,
    XXIV Symposium Electromagnetic Phenomena in Nonlinear Circuits,
    http://ptetis.put.poznan.pl/epnc/wp-content/uploads/2016/06/013.pdf

    A high voltage induction motor generates high magnitude currents during starting transient mode and in case of faults. These large currents produce excessive electromagnetic forces on end windings and induce stresses and vibrations. This paper presents an efficient way to compute the electromagnetic forces on end windings by 3D Finite Element Method (FEM) using Virtual Work (VW) principle. Besides, the computed forces are used for stress and vibration analysis by means of a Magneto-elastic coupling in an open source software Elmer. The force and stress distribution on end windings are imperious factors in the design process and normal and faulty operation analysis of motors.

  • Coupled electromagnetic-thermal simulation of the startup transient of a synchronous motor,
    Áron Szűcs, Mikko Lyly, Jan Westerlund,
    XXIV Symposium Electromagnetic Phenomena in Nonlinear Circuits,
    http://ptetis.put.poznan.pl/epnc/wp-content/uploads/2016/06/037.pdf

    Simulation of the electromagnetic-thermal coupling in the numerical analysis of electrical machines is an active academic research topic, for which there is also significant interest in the industry. One such interest case is the line starting of synchronous machines where thermal stresses are dynamic and significant. The coupling introduces an additional non-linearity in the electromagnetic simulation. The paper presents and discusses numerical formulations starting from 2D “weak-coupled” formulation, through 3D weak-coupled electromagnetic-thermal formulation, till 3D strong coupled simulations. Both the academic and industrial perspectives of the simulation capabilities and results are in the focus of the paper.

  • Electromagnetic transient finite element 3D modelling of electrical machines using open-source tools,
    Pavel Ponomarev,  Janne Keränen,  Pekka Pasanen,
    2016 XXII International Conference on Electrical Machines (ICEM) ,
    http://ieeexplore.ieee.org/document/7732746/

    This paper demonstrates a workflow for multi-physical simulation and design optimization of electrical machines using open-source tools. The workflow demonstrates applicability of open-source tools for all steps of complex 3D Finite Element Method modelling of an electrical machine – geometry production, meshing, pre-processing, solving (even in massively parallel environment), and post-processing with visualization. The example case is a permanent magnet synchronous machine with direct immersion oil cooling. First design simulation is demonstrated. The current-source driven electromagnetic simulation is used to estimate PM eddy-current losses and iron losses to evaluate the design.

  • Parallel Performance of Multi-Slice Finite-Element Modelling of Skewed Electrical Machines,
    Janne Keränen, Pavel Ponomarev, Jenni Pippuri, Peter Råback, Mikko Lyly, Jan Westerlund,
    IEEE Transactions on Magnetics,
    http://ieeexplore.ieee.org/document/7817828/

    The multi-slice method allows approximation of the 3-D phenomena without carrying out a full 3-D analysis, e.g., in skewed radial flux electrical machines. The idea is to divide a 3-D machine into several 2-D finite-element models along the axis, connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2-D models in modern parallel hardware. The results are shown to agree with 3-D computation and experimental results.

  • Multi-slice 2.5D modelling and validation of skewed electrical machines using open-source tools,
    Pavel Ponomarev, Janne Keränen, Mikko Lyly, Jan Westerlund, Peter Råback,
    2016 IEEE Conference on Electromagnetic Field Computation (CEFC),
    http://ieeexplore.ieee.org/document/7815918/

    This paper describes multi-slice modelling and validation of an axially skewed synchronous machine in 2D domain. The technique involves coupling of circuit and electromagnetic domains together with carefully constructed geometry. The model size in comparison with full 3D simulation reduces considerably. Developed 2.5D multi-slice model allows fast simulation in 2D domain, still taking into account 3D effect of skew on torque and back-EMF of the machine. Simulation results in 2.5D and 3D domains are compared to measurements. All simulations are performed using free and open-source tools.

  • Parallel performance of multi-slice method for skewed electrical machines
    Janne Keränen, Pavel Ponomarev, Jenni Pippuri, Peter Råback, Mikko Lyly, Jan Westerlund,
    2016 IEEE Conference on Electromagnetic Field Computation (CEFC),
    http://ieeexplore.ieee.org/document/7815921/

    Multi-slice methods allow us to approximate the 3D phenomena without carrying out a full 3D analysis, e.g. in skewed radial flux electrical machines. The idea is to divide a 3D machine into several 2D FEM models, only connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2D models in modern parallel hardware. The results are shown to match with 3D computation and experimental results.

  • Towards design of electrical machines from given air gap field
    Arto Poutala, Saku Suuriniemi, Timo Tarhasaari, Lauri Kettunen
    COMPEL – The international journal for computation and mathematics in electrical and electronic engineering,
    http://www.emeraldinsight.com/doi/full/10.1108/COMPEL-05-2016-0179

    The purpose of this paper is to introduce a reverted way to design electrical machines. The authors present a work flow that systematically yields electrical machine geometries from given air gap fields. The solution process exploits the inverse Cauchy problem. The desired air gap field is inserted to this as the Cauchy data, and the solution process is stabilized with the aid of linear algebra. The results are verified by solving backwards the air gap fields in the standard way. They match well with the air gap fields inserted as an input to the system. The paper reverts the standard design work flow of electrical motor by solving directly for a geometry that yields the desired air gap field. In addition, a stabilization strategy for the underlying Cauchy problem is introduced.

  • More to come