Hermann Lang

Validation of a Comprehensive Analytic Noise Computation Method for Induction Machines

The validation of an analytical approach to determine the noise behavior of induction machines is presented. Analytical electromagnetic, structural, and acoustical computations are performed. Data obtained by numerical computations as well as by vibration and noise measurements are compared with the analytical results.

Computation of the Noise Radiation of an Induction Machine Using 3D FEM/BEM

Purpose – The purpose of this paper is to set up a comprehensive numerical approach to estimate the 3D structural vibration and noise radiation of an induction machine.Design/methodology/approach – The rotating force waves, acting in the air gap of an induction machine and obtained by an electromagnetic finite element multi‐slice simulation, are applied to the 3D structural finite element model and a structural harmonic simulation is performed. The sound emission due to the vibration of the surface of the machine is computed with a 3D boundary element model.Findings – The paper outlays problematic issues when setting up the numerical models, i.e. the structural finite element model. The material properties strongly affect the structural behaviour and therefore the radiated noise.Originality/value – The 3D force distribution in the air gap and the resulting vibrations are computed. The structural behaviour, i.e. the different vibrational behaviour of stator and surface is discussed. The correlation of the ...

Numerical simulation of the end-winding deformations in the synchronous machine under symmetrical short-circuit conditions using FEM*

ZusammenfassungIn der Arbeit wird eine neuartige Methode zur Berechnung der Wickelkopfschwingungen unter Berücksichtigung von symmetrischen Kurzschlussbedingungen vorgestellt. Zur Lösung der elektromagnetischen und strukturmechanischen Problemstellung wird ein sequentiell gekoppeltes Simulationsverfahren im Zeitbereich verwendet. Zur Berechnung des zeitlich veränderlichen elektromagnetischen Feldes wird eine T, Φ – Φ – Formulierung der Finiten Elemente herangezogen. Dies ermöglicht die Berücksichtigung von induzierten Wirbelströmen in der Pressplatte, den Zahnfingern und allen relevanten Gehäuseteilen. Die Verwendung von nicht konformen Netzen führt dabei zu einer erheblichen Reduktion des Berechnungsaufwands. In der vorgestellten Simulationsmethode werden in jedem Zeitschritt die berechneten Lorentzkräfte der strukturmechanischen Simulation bereitgestellt. Diese Kräfte werden dann im Zentrum der Wickelkopfspulen als äußere Lasten vorgeschrieben. Zur Berechnung der räumlichen Deformationen dient ein übliches Zeitschrittintegrationsverfahren.SummaryIn this paper the numerical simulation of the end-winding deformations in a synchronous machine under symmetrical short circuit conditions is presented. A sequentially coupled numerical simulation between an electromagnetic and a structural mechanical problem has been carried out. Owing to the short-circuit conditions, both problems are to be computed in the time-domain. Analysis of the time-variant magnetic field has been performed using the T, Φ – Φ formulation for the finite element method (FEM). This way, the influence of the induced eddy currents in the clamping-plates and in the housing of the machine on the magnetic field in the end-region of the generator has been taken into the account. In order to reduce the computational time, the non-conforming finite element (FE) mesh approach has been used to solve the electromagnetic problem. In each time-step the Lorentz forces in the end-winding have been calculated and carried over to the structural-mechanical model. These forces have been applied in the centre of the end-winding bars in order to provoke the transient excitation for the mechanical structure. A time-stepping scheme has been applied to calculate end-winding deformations in each time-step.

Numerical simulation of electromagnetic and mechanical phenomena in the end-winding region of three-phase induction machines*

ZusammenfassungDie dreidimensionale Geometrie des Motor-Stirnbereichs, bestehend aus dem Wickelkopf, dem Gehäuse und ergänzenden Konstruktionsteilen, ist äußerst komplex und deshalb für analytische Berechnungen sehr schwer zugänglich. Die Komplexität der Geometrie erfordert darüber hinaus zeitaufwändige Modellierungen und rechentechnisch anspruchsvolle Simulationen. In dieser Publikation werden numerische Ansätze vorgestellt, die es erlauben, die Wickelkopf-Geometrie und die Rotorstrom-Erregung vereinfacht zu erfassen. Die Anwendung der gezeigten Methoden wird zunächst anhand der Berechnung der Wickelkopf-Streuinduktivitäten und der Wirbelstromverluste in den Pressplatten gezeigt. Zudem werden die mechanischen Verformungen des Wickelkopfes eines Synchrongenerators im Nennbetrieb untersucht. Für die Analyse des zeitvariablen Magnetfeldes wurde die T, Φ − Φ –Formulierung in Verbindung mit einer 3-D zeitharmonischen Finite-Elemente-Methode (FEM) angewandt.SummaryThe 3-D geometry of the motor end-region consisting of the end-winding together with the motor cross-section, housing and complementary construction parts is very complex, which makes the analytical computations of the electromagnetic phenomena related to the end-region very cumbersome and non accurate. Furthermore, owing to the complicated geometry, also the preparation of the numerical model is extremely time consuming and numerical simulation very computationally pretentious. The aim of this paper is to present the numerical approaches, which overcome these problems by introducing methods to simplify the modeling procedure of the machine end-winding and the consideration of the rotor current excitation. In this paper the use of the proposed methods is demonstrated by computing the induction motor end-winding leakage inductance, the computation of the eddy-current losses in the machine clamping-plates and by the calculation of the mechanical deformations of the synchronous generator end-winding under operating load conditions. Analysis of the time-variant magnetic field has been performed using T, Φ − Φ formulation for a 3-D time-harmonic finite element method (FEM).

Development of a new simulation tool for computation of the synchronous generator end-winding deformations

Computations and measurements of the end-winding deformations are extremely demanding tasks requiring an extended engineering knowledge, experiences, as well as computational and measurements resources. Furthermore, these kind of theoretical or empirical studies are rather time-demanding. The goal of this research work is to present, on the one hand, the development of an efficient computation tool based on T, Φ - Φ finite element formulation and, on the other hand, a measurement set-up based on laser vibrometer. Using these computational and measurement approaches, the end-winding deformations under fault conditions are computed and measured with a high efficiency and precision.

Validation of a comprehensive analytic approach to determine the noise behaviour of induction machines

The validation of an analytical approach to determine the noise behaviour of induction machines is presented. Analytical electromagnetic, structural and acoustical computations are performed. Data obtained by numerical computations as well as by vibration and noise measurements are compared with the analytical results.

Experimental investigation of the vibration behaviour of a laminated stack with winding

The vibration behaviour of a laminated stator core stack with windings and end windings is examined by carrying out detailed experimental investigations. Therefore, the stator core stack is excited with an electrodynamic shaker and the accelerations on the stators surface and end-windings are measured. With an experimental modal analysis the mode shapes of the structure are then obtained along with the frequency response functions. To determine the influence of the windings on the vibrational behaviour the results are compared to measurements on a laminated stack without the windings.