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A comment on No Magnets, Big Power: BMW’s Fifth-Generation Electric Motor (2022).

Re:No Magnets, Big Power: BMW’s Fifth-Generation Electric Mo... by DakotaR on Friday March 03, 2023 @12:02PM (#35012201)
That's really interesting that they picked brushes; Renault's EESM motors are similar but use wireless power transfer to excite the rotor windings. Maybe brushes can pass more current cheaply?
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Re:No Magnets, Big Power: BMW’s Fifth-Generation Electric Mo... by creeble on Friday March 03, 2023 @12:27PM (#35012579)
Yes, brushless necessitates more rotating mass plus the loss in the wireless exciter. Longer life (no brush changes or slip ring wear), but lower efficiency.

I wonder if a hybrid rotor would pay off? It would still need brushes, but the current could be less to make them last longer. Probably a problem with demagnetizing the fixed magnets or something.

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