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New motor for EVs

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Zero999:

--- Quote from: Wolfram on August 30, 2022, 06:00:05 pm ---
--- Quote from: Zero999 on August 29, 2022, 06:47:37 pm ---The main advantage appears to be the lack of expensive permanent magnets, which need to be rare earth for a powerful motor. There are other possible alternatives which have been looked at, but as far as I'm aware none have been used for any all EV.

--- End quote ---

The Tesla model S (at least some versions) use a copper rotor induction motor, and the Renault Zoe used a wound-rotor synchronous with sliprings for the magnetization as far as I know. The latter was used to allow demagnetization of the rotor, allowing the use of the motor windings and inverter as a charger.

Edit: some neat pictures of the Zoe rotor can be found here: https://paultan.org/2015/06/19/renault-zoe-new-electric-motor-cleon-plant/zoe-engine-plant-0040/ . It looks like it would develop significant reluctance torque as well, like an IPM rotor.

--- End quote ---
The stator has two pole pairs, so is it single phase, or two phase?

I would have thought having a wound rotor to create a DC field would burn up more energy, making it less efficient, than a rare earth permanent magnet motor? Perhaps it is less efficient, but not enough to matter?

T3sl4co1l:
Maybe. Strictly speaking, it's extra dissipation that you wouldn't have with PMs.  It might not be much: current can be reduced when less torque is required, giving reasonable efficiency in cruise.

Also allows some relaxation of gearbox requirements, as the field reduction likewise reduces EMF.  You need less of a VFD, or, it can spin much faster than available voltage at nominal RPM, if you don't mind that the torque is likewise lower.

The harmonic losses due to the salient-pole geometry could be more important; no idea.  Also depends how the stator is wound, I think.

Likely it's three phase; 4 poles just means those phases repeat twice around the circle.  So, 1800 RPM at 60Hz, like most commercial motors; what they choose to run it at is of course up to them.

Could potentially be quite fast (thus power-dense) if the lams are thin.  Thin lams would be a prerequisite of the charger mode operation.  Or maybe not, given its embarrassing efficiency in that mode, heh.  I mean, even if they're thin (like 0.07mm), the losses at some kHz are still considerable, so it's not like you have to switch very hard for that to be true, even if you work very hard to get the iron losses down (but while still using iron as such).

Hm, I suppose if they're doing a charger mode through there, they probably PWM the field in normal operation, to adjust it; seems like a massive wasted opportunity not to, at least.  So they might not be doing much VFD action at all; well, it's still required to avoid stator saturation of course, but above a certain frequency, voltage can level off (output waveform still sinusoidal -- or add back in whatever harmonics give least losses -- right, they don't necessarily need harmonic balance, nice) and field reduces instead.

Tim

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