This master’s thesis presents a measurement setup for determining the magnetic properties of soft magnetic toroidal samples. The first part provides the theoretical background on magnetic materials and the magnetization process in ferromagnetic materials. This is followed by a description of measurement methods for soft magnetic materials as defined by the IEC 60404 international standards series.
The experimental part details the measurement setup. The toroidal sample has two windings and operates as an open-circuit transformer. To ensure repeatability and comparability of the results, the magnetic field in the core must have an appropriate time-domain waveform. For this purpose, the MicroLabBox acquires the time-domain waveforms of the secondary voltage and the primary current, from which the waveforms of magnetic flux density and magnetic field strength are determined. Based on these measurements and the desired waveform, a PI controller regulates the output signal. The setup enables closed-loop control to maintain a sinusoidal waveform of either the secondary voltage or the primary current. Higher harmonics can be superimposed to synthesize arbitrary periodic waveforms.
A graphical user interface displays the status of the setup and allows tuning of the controller parameters and the reference signal. Due to the MicroLabBox’s constraints on data export, high-resolution data acquisition is performed using an external data acquisition device.
The operation of the setup is demonstrated by characterizing core losses in different regions of a stator lamination, which may differ due to material processing. Rolling induces mechanical stresses that lead to magnetic anisotropy, whereas punching or laser cutting damages the crystal structure at the edges, locally degrading magnetic properties. This effect is more pronounced in narrower parts of the lamination. The setup supports measurements on toroids of various widths under a wide range of magnetic conditions, enabling more accurate loss characterization.
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