Mathias Mair

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...

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.

Modeling of a rotor of an electrical machine using composite beam elements

The vibrations of a rotor in an electrical machine are investigated with one-dimensional finite elements. The elements have six degrees of freedom and are described by Timoshenkos beam theory. The shear correction factors are computed from a separate finite element problem for each cross section. Composite elements balance the heterogeneous structure of the rotor. The results of a modal analysis are compared to experimental data in order to validate the rotor model. Finally, the rotating system is analyzed including the gyroscopic effect and spin softening.

A full structural mechanical description of beam elements for rotors in electrical machines

Purpose – The purpose of this paper is to get a more consistent finite element description for three-dimensional (3D) Timoshenko beam elements. It extends the common description of beam elements by modifying the shape functions and considers the warping of the cross-section due to torsion. Design/methodology/approach – The paper builds mainly on a finite element description of 3D Timoshenko beam elements. The implementation of high-order shape functions for torsion is done by adding a seventh degree of freedom to the system. Findings – The results reveal that for some beams, depending on their physical dimensions, the warping of the cross-section has large influence. In comparison to a conventional FE program, the extended finite element description considers the warping and yields more accurate results. Practical implications – An application of the extended finite element description is done with an implementation of the code in MATLAB. The static and dynamic behavior of a rotor in an electrical machine...

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.