Exploring higher-order harmonic eddy current in soft magnetic composites

초록

Electric motors, as the key building blocks of electric vehicles require high power density to enable driving over long distances with minimal power loss. In this regard, considerable research efforts have focused on searching for new magnetic materials, with soft magnetic composites (SMCs) considered promising. However, the eddy currents generated in SMCs are the primary contributors to power loss owing to their induced magnetic field reduction, harmonics that can distort the power waveform, and overheating. While eddy currents have been sufficiently investigated at the macroscopic level, information on their microscopic characteristics and contributions, particularly those depending on harmonic orders, has remained elusive. Here, we propose a systematic way to explore in detail the harmonics of eddy currents in two model systems including a power inductor and iron powder disk, using the atomic force microscopy based technique, so called multidimensional magnetic force microscopy (MMFM). Using MMFM, we show key effects of harmonics related to eddy currents by unveiling each contribution toward magnetic signals. In particular, the MMFM images show local variations in the nth harmonic of the eddy current signals within the spatially mapped magnetic features. These results show the proposed approach is effective to explore the harmonics of eddy currents, offering fundamental insight for development of highly efficient electric motors.

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