Christoph Schlensok

iMOOSE-an open-source environment for finite-element calculations

Implementing finite-element (FE) solvers for new formulations is often a tedious task, as many common parts are coded again and again. Also, commercial codes are often expensive and therefore difficult to include in, e.g., a teaching environment. iMOOSE is an open-source software package for FE calculations that tries to solve these issues. It is a general-purpose class library that allows for an easy implementation of new FE solvers or FE-related tools. Also included are ready-to-use solvers for electromagnetic calculations and a powerful post-processing tool. Due to its open-source nature, the source code can be examined, modified, and extended to fit the users needs.

Combined numerical and analytical method for geometry optimization of a PM motor

For the reduction of the cogging torque of permanent-magnet synchronous machines several approaches are known. But cogging torque predictions for arbitrary types of machines using the same approach are still troublesome and imprecise. Therefore, a fast optimization process is developed and presented in this paper. Here, the combination of both numerical and analytical simulation results in such a fast method

Acoustic simulation of an induction machine with squirrel‐cage rotor

Purpose – To present results of research closely linked to real life applications and to resume the work of a period of a few years.Design/methodology/approach – The combination of finite‐element method (FEM) and boundary‐element method is applied to simulate the electromagnetic, mechanical, and acoustic behaviour of an induction machine with squirrel‐cage rotor. The paper gives an overall view of the workflow and the implemented mathematics, starting off with the two‐dimensional, transient electromagnetic simulation and the succeeding three‐dimensional, static electromagnetic simulation. Theory and results of the mechanical and acoustic simulations are discussed.Findings – A main result of the research work is that the simulation of the acoustic behaviour of an electrical machine is very time‐consuming. Furthermore, geometry adoption, especially of the mechanical model, is very sensible.Research limitations/implications – Using the FEM for simulation of structure dynamic problems is often limited to how ...

Comparison of 2-D and 3-D Coupled Electromagnetic and Structure-Dynamic Simulation of Electrical Machines

For the coupled electromagnetic and structure-dynamic simulation of electrical machines, various 2D and 3D techniques are available. This paper reviews and compares them. The strength as well as the weaknesses of these methods are pointed out. Numerical results for the analysis of a switched reluctance machine (SRM) as an example evaluate accuracy and computational effort. It shows that the 2D simulation gives quite accurate results, as long as the axial effects and 3D mode shapes are not relevant.

Electromagnetically excited audible noise – evaluation and optimization of electrical machines by numerical simulation

Purpose – Disturbing vibrations and noise of electrical machines are gaining impact. The paper aims to focus on the necessity of estimating the electromagnetic, structure‐dynamical, and acoustic behaviour of the machine during designing and before proto‐typing.Design/methodology/approach – An adequate tool is numerical simulation applying the finite‐element method (FEM) and the boundary‐element method (BEM) allowing for the structured analysis and evaluation of audible noise also caused by manufacturing tolerances.Findings – The simulated results show good accordance to measurement results. The methods and simulation tools allow the analysis and evaluation of every type of energy converter with respect to its electromagnetic, structure‐dynamical and acoustic behaviour.Originality/value – The methods developed and proved can be applied to any electromagnetic device in general.

Calculation of force excitations in induction machines with centric and excentric positioned rotor using 2-D transient FEM

The calculation of induction machines with squirrel cages using the finite-element method (FEM) requires a transient solving process. The rotation has to be taken into account. Therefore, a rotating air gap is implemented. The formulation for the transient solver is given. Finite-element models of an induction machine with centrical and excentrical positioned rotor are calculated. The formulation for the computation of the surface force density on the stator teeth is presented. For both variants of the induction machine, the forces are calculated and compared.

Body-Sound Analysis of a Power-Steering Drive Considering Manufacturing Faults

The acoustic noise and the mechanical behavior of electrical machines gain significance day by day. Applying electrical machines such as induction machines with squirrel-cage rotors (IMs) as power-steering drives in automotive applications requires very strict constraints for the behavior of the motor for both electromagnetic and mechanical means. Therefore, it is of particular interest to analyze the machines behavior in both means, depending on the technical faults that are caused by manufacturing processes and unavoidable mechanical tolerances. The studied IM is a mass series product and does not allow for expensive manufacturing. Hence, the impact of the technical faults must be estimated and contained. Finite-element models allow for a structured but complex analysis of these tasks.

Comparison of static, dynamic, and static‐dynamic eccentricity in induction machines with squirrel‐cage rotors using 2D‐transient FEM

Finite‐element simulations of induction machines with squirrel‐cage rotor require transient solution algorithms. For this reason a transient 2D solver is utilized which takes rotational movement of the rotor into account. Its formulation and the time‐step algorithm are given. Two different kinds of eccentricity of the rotor and their combination are defined and studied. The three motor variants are computed and the torque, the net force, and the surface‐force density are compared in time and frequency domain.

Stator optimization of six-phase claw-pole alternators using asymmetric winding arrangements

Purpose – To present a new approach for improvement and optimization of synchronous claw‐pole alternators without changing the general machine design.Design/methodology/approach – Various changes on the magnetically relevant parts of the machine design have been discussed formerly to achieve improved electromagnetic and acoustic behavior. The electrical part of the machine is considered in this paper, varying the stator winding arrangement to achieve optimized behavior.Findings – Provides information about motivation and the methodology of the optimization process. Presents the entire analysis, covering idea, technical and computational implementation as well as verification.Research limitations/implications – It describes a method based on the utilization of specific, partly self‐generated software, which perhaps limits its usefulness if mentioned tools are unavailable. However, the presented basic method is to be used generally.Originality/value – This paper presents a promising approach to further opti...

Cogging-Torque Analysis on Permanent-Magnet Machines by Simulation and Measurement (Analyse des Rastmoments von permanentmagneterregten Maschinen mittels Simulation und Messung)

Cogging torque is an effect to be considered in the design and optimization process of Permanent-Magnet Machines (PMM). Many simulation methods have been proposed. Verification of provided results require measurements of the cogging torque. Measuring it is, though, no easy task. Existing measurement setups often do not decouple the influence of the drive and the measured PMM. Hence, we propose a simple yet accurate test bench design for the measurement of cogging torque. The studied PMM is simulated using the Finite-Element Method (FEM) numerically, and the results are compared. Rastmomente müssen bereits im Auslegungsprozess von permanentmagneterregten Maschinen (PMM) berücksichtigt werden. Es gibt eine Vielzahl von Simulationsmethoden. Die Verifizierung von Ergebnissen erfordert eine Messung des Rastmoments. Die Rastmomentmessung ist jedoch keine leichte Aufgabe. Bestehende Messaufbauten entkoppeln meist den Einfluss von Antrieb und PMM nicht hinreichend. Daher wird ein einfacher und genauer Messaufbau zur Messung von Rastmomenten vorgestellt. Eine der untersuchten PMMs wird zudem mittels FEM numerisch simuliert. Die Ergebnisse werden mit denen der Messungen verglichen.