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Article

Selection of Optimal Magnets for Traction Motors to Prevent Demagnetization

1
MagWeb USA, Frisco, TX 75035, USA
2
MAGNA Powertrain GmbH, 2514 Traiskirchen, Austria
*
Author to whom correspondence should be addressed.
Academic Editor: Antonio J. Marques Cardoso
Machines 2021, 9(6), 124; https://doi.org/10.3390/machines9060124
Received: 20 May 2021 / Revised: 15 June 2021 / Accepted: 16 June 2021 / Published: 20 June 2021
(This article belongs to the Section Vehicle Engineering)
Currently, permanent-magnet-type traction motors drive most electric vehicles. However, the potential demagnetization of magnets in these motors limits the performance of an electric vehicle. It is well known that during severe duty, the magnets are demagnetized if they operate beyond a ‘knee point’ in the B(H) curve. We show herein that the classic knee point definition can degrade a magnet by up to 4 grades. To prevent consequent excessive loss in performance, this paper defines the knee point k as the point of intersection of the B(H) curve and a parallel line that limits the reduction in its residual flux density to 1%. We show that operating above such a knee point will not be demagnetizing the magnets. It will also prevent a magnet from degenerating to a lower grade. The flux density at such a knee point, termed demag flux density, characterizes the onset of demagnetization. It rightly reflects the value of a magnet, so can be used as a basis to price the magnets. Including such knee points in the purchase specifications also helps avoid the penalty of getting the performance of a low-grade magnet out of a high-grade magnet. It also facilitates an accurate demagnetization analysis of traction motors in the worst-case conditions. View Full-Text
Keywords: traction motors; electric vehicle (EV); permanent magnets; knee point; demagnetization curve; severe duty; short-circuit fault; IDF; magnetic field analysis; reversible segment; heat-resistant magnet traction motors; electric vehicle (EV); permanent magnets; knee point; demagnetization curve; severe duty; short-circuit fault; IDF; magnetic field analysis; reversible segment; heat-resistant magnet
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MDPI and ACS Style

Rao, D.; Bagianathan, M. Selection of Optimal Magnets for Traction Motors to Prevent Demagnetization. Machines 2021, 9, 124. https://doi.org/10.3390/machines9060124

AMA Style

Rao D, Bagianathan M. Selection of Optimal Magnets for Traction Motors to Prevent Demagnetization. Machines. 2021; 9(6):124. https://doi.org/10.3390/machines9060124

Chicago/Turabian Style

Rao, Dantam, and Madhan Bagianathan. 2021. "Selection of Optimal Magnets for Traction Motors to Prevent Demagnetization" Machines 9, no. 6: 124. https://doi.org/10.3390/machines9060124

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