Moore, Martina ; Roth, Stefan ; Gebert, Annett ; Schultz, Ludwig ; Gutfleisch, Oliver (2015)
The effect of surface grain reversal on the AC losses of sintered Nd–Fe–B permanent magnets.
In: Journal of Magnetism and Magnetic Materials, 375
doi: 10.1016/j.jmmm.2014.09.047
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
Sintered Nd–Fe–B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd–Fe–B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2015 |
| Autor(en): | Moore, Martina ; Roth, Stefan ; Gebert, Annett ; Schultz, Ludwig ; Gutfleisch, Oliver |
| Art des Eintrags: | Bibliographie |
| Titel: | The effect of surface grain reversal on the AC losses of sintered Nd–Fe–B permanent magnets |
| Sprache: | Englisch |
| Publikationsjahr: | 1 Februar 2015 |
| Verlag: | Elsevier Science Publishing |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Journal of Magnetism and Magnetic Materials |
| Jahrgang/Volume einer Zeitschrift: | 375 |
| DOI: | 10.1016/j.jmmm.2014.09.047 |
| Kurzbeschreibung (Abstract): | Sintered Nd–Fe–B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd–Fe–B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory. |
| Freie Schlagworte: | NdFeB, Loss, Electric motor, Eddy current |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Funktionale Materialien 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften |
| Hinterlegungsdatum: | 17 Nov 2014 10:00 |
| Letzte Änderung: | 17 Nov 2014 10:00 |
| PPN: | |
| Sponsoren: | The work was funded by the ‘Forschungsvereinigung Antriebstechnik e.V. (FVA)’, Frankfurt/Main, Germany. |
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