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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 control based on the load history and maximum permissible temperatures. Consequently, the machine's capabilities can be exhausted at best considering a highly-utilized drive. The model shall be as simple as possible without sacrificing the exactness of the predicted temperatures. Accordingly, a specific lumped parameter thermal network topology was selected and its characteristics are explained in detail. The measurement data based optimization of its critical parameters through an evolutionary optimization strategy, and the therefore utilized experimental setup will be described in detail here. Measurement cycles were recorded for modeling and verification purposes including both static and dynamic test cycles with changing load torque and speed requirements. Applying the proposed hybrid approach for determining the model's parameters through involving physics-based equations as well as numerical optimization followed a significant improvement of the preciseness of the predicted motor temperatures compared to solely determining the networks's coefficients based on expert knowledge. Thereby, the validation included both the original measurement data as well as extra measurement runs. The proposed and applied strategy provides an excellent basis for future thermal modeling of electric machines.

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 for multi-harmonic currents evaluation is derived. Consequently, an interior-rotor IPM machine is studied. In order to have a fair comparison with conventional PMSMs featuring sinusoidal currents, an optimization scenario is defined where the same outer dimensions as well as magnet and copper volume for both design variants are considered. The use of multiple current harmonics requires a dedicated strategy for evaluating machine designs, as the conventional dq -grid analysis cannot be utilized. The introduced approach is applied and results of the optimization are illustrated. Prototypes were manufactured and machine designs were subsequently evaluated through experiments. A valuable lesson learned during practical implementation regarding rotor angle determination is highlighted. Measurement results reveal that adding more degrees of freedom in terms of multiple harmonics can give significant improvements for performance measures efficiency and torque ripple. This particularly holds if the harmonics are already considered throughout the machine design and optimization process, rather than only at post-processing stage. Version of record

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 winding system are presented. Version of record

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 measurement system is derived. Finally, the concept as well as the modeling chain are verified through measuring and modeling simplified material mixtures. Version of record