"It's a big advance in terms of the efficiency of the electric motor, while getting away from the use of rare earth minerals."
Their reasoning:
"Permanent magnet machines typically rank as the most power-dense electric motors, but there's no turning permanent magnets "off." Their magnetic fields never change, so when they're not being powered by energy in the stator winding, they're generating energy in those windings, which creates drag."
I think BMW's implementation of one pedal driving uses front radar and map info to adapt between coasting and regen as needed to get the most efficiency.
Their existing ICE cars also have a coast mode where they disconnect the engine from the transmission when you're not giving it gas (to eliminate engine braking). That function is only active when you put the car in eco mode. It's surprisingly smooth and responsive, you can't really feel the engine disconnect and reconnect as you're driving.
[1]: https://www.goudsmitmagnets.com/en/solutions/magnetic-handli...
In other words, yes, possible, but more complicated than one might think. For example, we could build a circuit that "sucks out" the field by jamming very high currents in the opposite direction through the coils. To do this needs even higher voltages that the motor normally uses.
So, yes, it's possible. Not especially easy for optimal efficiency.
After driving an EV for a while now, coasting is the number one thing that drives me crazy when driving an ICE car. It just isn't something that my mind thinks about anymore, so when it happens, it's a bit jarring at first. My wife's profile in my car is set to "coast" mode because she is the opposite. Her primary car is an ICE, so when she is driving my EV, it is jarring for her too!
I guess, for me, this would really have an impact on highway driving. So, in the magnet-less design, are they saying that you are more efficient because your motor won't pull away energy/speed when not powered? As opposed to a permanent-magnet design, where you have to constantly add energy to maintain speed?
That's one quick explanation for how a magnet-less design might be more efficient... but I'm still not sure if it is right... and at non-highway driving (changing speeds frequently), I'd rather have the better one-pedal control.
Yes. And the magnetless motors are still able to regen when you want to slow down.
Turns out in typical car use, the efficiency gains when driving outweigh the losses from this.
Pretty much anything where the generator speed isn't 50/60Hz fixed uses something with permanent magnets.
However you design it, a magnet creates a magnetic field with zero power use, whereas any other source of magnetic field generation ends up using electrical power, generating heat (in a part hard to cool), and usually heavier for the same torque.
I'm disappointed that BMW doesn't give efficiency figures in their press release, because that is what has been pushing everyone else to the various kinds of BLDC/SynRM machines.