Gerd Bramerdorfer

• PhD
• Full Professor at Johannes Kepler University of Linz

Purpose This paper aims to investigate the reliable thickness, and more generally, the geometric and material parameter determination of thin electrically conductive and diamagnetic coatings on conductive and ferromagnetic substrates, e.g. steel, using eddy current testing (ECT). Design/methodology/approach The analytical model of an ECT coil arra...

The inherent nonlinear attribute introduces numerous uncertainties in the design process of switched reluctance motors (SRMs). Thus, in this article, a novel design theory with unambiguous symbols based on the nonlinear characteristic is proposed for SRMs. First, the speed–torque design requirements and the control methods are incorporated into the...

Evolutionary algorithms and related mutation-based methods have been used in software engineering, with recent emphasis on the problem of repairing bugs. In this work, programs are typically not synthesized from a random start. Instead, existing solutions—which may be flawed or inefficient—are taken as starting points, with the evolutionary process...

Modelling and controlling heat transfer in rotating electrical machines is very important as it enables the design of assemblies (e.g., motors) that are efficient and durable under multiple operational scenarios. To address the challenge of deriving accurate data-driven estimators of key motor temperatures, we propose a multi-objective strategy for...

Featured Application The results of this work can be included in the design stage of modular permanent magnet synchronous machines for fault-tolerant applications. Abstract Addressing stator-rotor misalignment, usually called eccentricity, is critical in permanent magnet (PM) machines since significantly high radial forces can be developed on the...

Surrogate model (SM)-based optimization approaches have gained significant attention in recent years due to their ability to find optimal solutions faster than finite element (FE)-based methods. However, there is limited previous literature available on the detailed process of constructing SM-based approaches for multi-parameter, multi-objective de...

This work is about a nondestructive electromagnetic measuring concept to determine the chemical composition of multi-phase bulk materials, e.g. direct reduced iron, in industrial applications by using a model-based estimator. The required mathematical model consisting of an effective medium approximation and an electromagnetic model of the measurem...

Switched reluctance machines (SRMs) provide a potential candidate and a feasible solution with increased interest for industrial applications due to their simple and rigid structure without permanent magnets, low manufacturing cost, excellent power-speed characteristics, and high reliability. However, the nonlinear inductance/flux linkage character...

This paper presents the characterization of the magnetic properties of laminated cores for electrical machines at ambient and cryogenic temperature. Silicon-iron stator cores of different steel grades are characterized experimentally at room temperature and when immersed in a liquid nitrogen atmosphere. The magnetic characterizations involve the me...

In the automotive market and automation industry, the race for ever increasing power and energy densities of electric motors leads to an endeavor of developing real-time-capable thermal models. The precise thermal monitoring of critical motor components promises material reduction and higher material utilization. Among classical, expert-based, lump...

This work evaluates the impact of the winding system on the accuracy of the soft magnetic material (SMM) characterisation using ring shaped specimen by means of finite element simulations. The quantified correlations are validated through measurements. In addition, the gained insights are discussed and hand on guidelines for the design of said wind...

The use of interlocks often represents an affordable stacking solution for soft magnetic cores in mass production of electrical machines. However, due to the process itself, the material behavior and thus the resulting electrical machine performance is negatively impacted. On the one hand, this is due to additional conductive paths, which increase...

Ferromagnetic materials may be affected by the presence of local losses due to defects or magnetic anomalies caused by machining processes. To highlight such anomalies is not easy; a noninvasive thermographic method has been refined to allow a proper comparison of different machining processes’ impact on the iron losses. Specimens obtained with pun...

Conventionally, the small mean and variance of peak-to-peak cogging torque of permanent magnet (PM) machines considering manufacturing uncertainties can be achieved by a robust design or by reducing the uncertainties range. However, the consequent compromise of other design objectives or the increase in the manufacturing costs are frequently inevit...

One of the main obstacles to the robust optimization for permanent magnet machines is the high computational burden, which is mainly caused by the robustness evaluation considering the manufacturing uncertainties. In this paper, a sequential sampling Kriging model is adopted to estimate the design robustness, and the problem of high-dimensional var...

Switched reluctance motors (SRMs) have attracted considerable attention for energy conversion within industrial applications. To realize the high-quality operation status, optimization for SRMs is one of the most essential steps in the design stage. In this paper, a multi-objective design optimization method is proposed for a novel SRM with unequal...

This article is about investigating the potential of multi-harmonic design of permanent magnet synchronous machines. Thereby, multi-harmonic refers to the temporal periodic characteristics of linked fluxes and currents of the stator phases in order to ensure high-efficient operation with very low torque ripple. At first, a suitable model allowing f...

This work is on deriving precise lumped parameter thermal networks for modeling the transient thermal characteristics of electric machines under variable load conditions. The goal is to facilitate an accurate estimation of the temperatures of critical machines' components and to allow for running the derived model in real time to adapt the motor co...

This paper presents a detailed process for the design of interior permanent magnet synchronous machines (IPMSMs) for electric vehicle (EV) applications. First, a comprehensive design process featuring two objectives and three constraints is proposed to realize an optimal IPMSM design that can satisfy the key performance requirements for an EV appli...

This paper presents a comparison of optimized tooth-coil-winding modular permanent-magnet synchronous machines (TCW-MPMSMs) with H-shape and U-shape stator segments for fault-tolerance applications. Four optimization objectives are studied by means of a Particle-Swarm-Optimization (PSO) based routine: maximum rated torque, minimum torque ripple, ma...

An optimally designed line-start permanent magnet synchronous machine may require a different squirrel-cage design than traditional induction machines. The objective of this paper is to apply topology optimization based on the normalized Gaussian network in order to find the optimal shape of the rotor bars for a line-start permanent magnet synchron...

This paper investigates and compares two popular combined winding configurations for bearingless machines, the multi-phase (MP) and dual-purpose no-voltage (DPNV) windings. Each of these winding configurations has the ability to independently create suspension force and drive torque using the same stator coils. The paper develops analogous bearingl...

In this paper, a new system-level sequential Taguchi method (SLSTM) is proposed to achieve the optimal solution with high robustness for switched reluctance motor (SRM) drive systems. An SRM drive system consisting of a segmented-rotor SRM and the angle position controller is investigated as a case study. In the implementation, the optimization fun...

This paper reviews the recent developments of design optimization methods for electromagnetic devices, with a focus on machine learning methods. First, the recent advances in multi-objective, multidisciplinary, multilevel, topology, fuzzy, and robust design optimization of electromagnetic devices are overviewed. Second, a review is presented to the...

This paper introduces the design and optimization of line-start synchronous machines in fractional horse power industry applications. The proposed optimized design will be considered as a replacement for the induction machine driven from an AC drive. The optimized design will be achieved using a 2D finite element transient analysis and multi-object...

This paper discusses a method to consider the effects of the manufacturing uncertainties on the cogging torque harmonics, with which a sensitivity analysis can be incorporated into the design stage instead of just checking it afterwards. With the authors' previous work of the worst-uncertain-combination-analysis (WUCA) method, several design parame...

The papers in this special section intends to collect ideas and recent advances from the global community in the field of improving robustness to uncertainty in the modelling, analysis and design of electric machines and drives, making possible the development of appropriate models for such components. When modelling electromechanical devices, elec...

This work is about the analysis and optimization of radial flux modular stator synchronous machines. An outer rotor topology with surface-mounted permanent magnets is focused. The stator holds concentrated coils fixed to U-shaped segments made of laminated steel. An automated procedure for evaluating the characteristics of any design variant of thi...

This paper analyzes the impact of manufacturing tolerances on the cogging torque of a 24-slot 28-pole tooth-coil-winding permanent magnet synchronous machine with a modular stator core (TCW-MPMSM). Dimensional tolerances and asymmetries associated with the modular topology are studied by means of finite element simulations in order to identify key...

In the field of electrical machine design, excellent performance for multiple objectives, like efficiency or torque density, can be reached by using contemporary optimization techniques. Unfortunately, highly optimized designs are prone to be rather sensitive regarding uncertainties in the design parameters. This paper introduces an approach to rat...

This work is about analyzing surface mounted permanent magnet machines regarding their sensitiveness related to erroneous magnet positioning. A finite element analysis based approach is presented and different topologies in terms of slot and pole count are compared. The study further includes the analysis of multiple magnet widths and stator teeth...

This paper presents a semi-analytical finite element method to derive the slot leakage inductance of rotating electrical machines with double-layer windings. The proposed method combines the lower computational burden of analytical equations and the accuracy/flexibility of the finite element method. Moreover, only a two-dimensional finite element s...

According to the special section entitled ‘Robust design and analysis of electric machines and drives’, to be published in IEEE Transactions on Energy Conversion, the authors present an introduction to tolerance analysis, robust optimization, and measures to improve the reliability of electric machines, power electronics and drives, and their robus...

In this paper, a novel system-level robust design optimization method is presented to improve the performance of switched reluctance motor (SRM) drive systems under multiple operating conditions. Based on typical driving cycles of electric vehicles (EVs), five typical driving modes of the SRM are determined. The optimization objectives in each driv...

This paper presents a new method for multi-objective robust design optimization of electrical machines and provides a detailed comparison with so far introduced techniques. First, two robust design approaches, worst-case design and design for six-sigma, are compared with the conventional deterministic approach for multi-objective optimization. Thro...

This paper presents a comparative study on different types of robust design optimization methods for electrical machines. Three robust design approaches, Taguchi parameter design, worst-case design and design for six-sigma, are compared for low-dimensional and high-dimensional design optimization scenarios, respectively. For the high-dimensional sc...

This article is about illustrating a workflow for incorporating reliability measures to typical electric machine design optimization scenarios. Such measures facilitate comparing designs not only for rated conditions, but also allow to analyze their performance in the presence of unevitable tolerances. Consequently, by additionally considering reli...

Investigating the impact of tolerance-affected parameters on the performance of electric machines gets evermore important. A major reason is that designs are optimized and thus are on or close to boundaries regarding performance constraints. Moreover, highly-utilized designs are obtained due to optimization of cost or specific measures like torque...

This article is about analyzing the change of the optimal design's shape and respective performance measures of permanent magnet synchronous machines considering the manufacturing impact on soft magnetic materials. Typically, the respective material degradation is neglected when optimizing electric machines. However, recent studies reported a signi...

We describe initial attempts to model the dynamic thermal behavior of electrical machines by evaluating the ability of linear and non-linear (regression) modeling techniques to replicate the performance of simulations carried out using a lumped parameter thermal network (LPTN) and two different test scenarios. Our focus falls on creating highly acc...

This paper presents an analysis of a permanent magnet synchronous machine (PMSM) with an unequal teeth width. The use of the concentrated nonoverlapping winding, also known as tooth-coil winding, has certain advantages. In addition, asymmetric features can be exploited by adopting this winding configuration to improve the machine performance. The p...

This paper focuses on the numerical implementation of a continuous model for local degradation in soft magnetic materials. Cutting and punching processes required for producing electric machines impact the magnetic properties of soft magnetic materials. A simplified but effective model for considering local degradation of soft magnetic materials is...

This article is about a comparison of different measures for determining the robustness or reliability of electric machine designs in the presence of inevitable tolerances. The selected criteria shall be suitable for concurrent evaluation in the course of solving state-of-the-art large scale multi-objective optimization problems. In the past, besid...

In the recent past, several successful experiences to modify standard efficiency induction motors in Premium efficiency class (IE3) machines have been presented, considering simple and low-cost changes in the design and production processes. However, this approach — also known as no-tooling-cost process — seems to have reached its limit without off...

This article is about investigating the tolerance sensitiveness of electric machines regarding permanent magnet failures. The focus is on established permanent magnet synchronous machine designs in terms of slot and pole count. A finite-element-based approach is presented that allows analyzing single air-gap magnetomotive force (MMF) harmonics and...

— This paper compares different surface-mounted and flux-switching PM machine structures for automotive applications. At first, both structures are designed considering as relevant the final total cost of the used materials. Axial and radial flux magnetic structures have been taken into consideration for both machines. The performance of the four m...

Manufacturing processes such as cutting, welding or assembling originate mechanical and thermal effects that locally introduce residual stresses. Consequently, the magnetic material shows a decrease of magnetic permeability and an increase of hysteresis losses. The adoption of catalogue data for electrical machines simulation thus follows low accur...

This paper presents an analytical model of U-shape tooth-coil-winding modular permanent magnet synchronous machines (TCW-MPMSMs) in terms of main design parameters. Analytical expressions for the flux density distribution, back EMF, and electromagnetic torque were derived. 2-D finite element (FE) simulations for a 24-slot 28-pole machine for severa...

The first of this two-part article illustrates the state-of-the-art in soft magnetic materials characterization starting with very early developments and giving a retrospective view of research carried out in this field. One famous measurement setup is the Epstein frame, named after Josef Epstein. Around 1900, he published a German article about “T...

The first part of this two-part article is about a retrospective view of material characterization, starting with the work of J. Epstein around the year 1900 and respective basic explanations. Consequently, the work presented herein is about the current state-of-the-art, recent developments, and future trends in characterization of ferromagnetic ma...

Electric machine design optimization is a popular topic in electrical engineering. Thanks to major accomplishments in Mathematics and Computer Science, nowadays the investigation of thousands of designs for particular optimization tasks is possible. Huge effort is made for developing evermore complex multi-physics simulation models including, e.g.,...

This paper focuses on a new structure of permanent magnet machines suitable for highly integrated in-wheel motors for vehicle application. In particular, the main feature of the integrated solution lays in the removal of a sector of the stator in order to have the required space for the brake caliper. However, the sectored-stator introduces an addi...