Bernhard Weilharter

Weak Coupling Between Electromagnetic and Structural Models for Electrical Machines

A weak coupling technique for an electromagnetic and a structural dynamic model formulated by the finite element method (FEM) is presented. The algorithm is able to estimate higher force harmonics with high accuracy and is hence suitable for acoustic simulations of electrical machines. High computational efforts using conventional algorithms are reduced significantly and accuracy is even enhanced. The algorithm is applied to compute vibrations of a skewed induction machine.

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 Rotating Force Waves in Skewed Induction Machines Using Multi-Slice Models

Investigations of the noise behavior of induction machines demand the calculation of the rotating force waves and thus the determination of the field-harmonics. The goal of this paper is to develop a method to compute the field-harmonics of a skewed induction machine using a multi-slice model.

Numerical and experimental investigation of the structural characteristics of stator core stacks

Purpose – The purpose of this paper is to analyse the eigenforms and eigenfrequencies of stator core stack by experimental and numerical investigation. The influence of material parameters on the structural vibrations is carried out in order to describe the laminated structure of stator core stack with a homogeneous material model. Design/methodology/approach – The finite element method is applied for a numerical modal analysis. Therefore, a homogeneous transversally isotropic material model is introduced and the influence of each material parameter on the dynamical behavior is investigated. These material parameters are stepwise adjusted to the results from the experimental modal analysis. The investigation includes results from different stator core stacks. Findings – The influence of material on the modal parameters is shown. Furthermore, material parameters are carried out for stator core stacks, which describe the measured dynamical behaviour. Originality/value – The presented investigations show a u...

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 ...

Frequency Domain Evaluation of Transient Finite Element Simulations of Induction Machines

A comprehensive procedure for the frequency domain evaluation of transient finite element simulations of induction machines is presented. The proposed algorithm allows the determination of the magnetic air-gap flux density for arbitrary operational points under consideration of the rotor movement. The flux density harmonics can be determined on the stator as well as on the moving rotor surface. For skewed induction machines, an interpolation algorithm for the axial behavior of the flux density is included. The procedure is demonstrated for a skewed induction machine operating at nominal load.

Numerical investigation of the 3D vibrational behaviour of skewed induction machines due to rotating force waves

Purpose – The purpose of this paper is to analyse the surface vibrations of an induction machine due to force waves acting on the stator and rotor core. The focus lies on the investigation of the influence of force waves with axial variation and with higher spatial ordinal numbers on the surface vibration of an induction machine and thus its emitted noise.Design/methodology/approach – Unit force waves with different spatial ordinal numbers and varying in axial direction are set up and applied on the stator and rotor teeth of a structural finite element model of an induction machine. Structural harmonic analyses with different frequencies are performed and the deformation of the machine is determined. After that, the root mean square of the normal component of the velocity on the surface of the machines housing is determined and compared for the different force waves.Findings – The influence of force waves with spatial ordinal numbers of higher order can have a significant influence on the structural vibr...

Rotor Vibrations in Electrical Machines Due to Electromagnetic Forces

The rotor vibrations caused by rotor unbalance and electromagnetic forces are investigated for a two-pole induction machine. Using Timoshenko beam elements, the heterogeneous assembly of the rotor is modeled and the different material properties are considered. The nonlinear simulation includes effects of rotor unbalance and the unbalanced magnetic pull (UMP). Machine parameters influencing the unbalanced magnetic pull are varied to analyze their impact on the rotor vibration.

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.