A 17-year-old engineer's magnet-free motor prototype could make electric vehicles more sustainable

[seuadr]

it isn't that the internet is dead, it is that there are a lot of brain dead people on the internet

BBS is how i was introduced to the concept of the internet around.. oh. 1994 or so - both through delphi internet(which is actually still online?! - and oh my god i still remember my password) and local ones to michigan. Man, memory lane.

my first username was actually because i didn't understand an Ad i saw for the X-Files usenet group on delphi - it said to enter WRJ95 as the password, but, i messed up and entered it as the username, and then ended up creating a new account and well, i haven't really logged off since

[serialk11r]

Magnet-less SRMs put more demand on the controller. You lose cost in the motor in exchange for more cost in the controller. Torque ripple (lots of noise, think vacuum cleaner, hand dryer) is probably unacceptable to most car owners.

Elon's idea of using induction motors was actually pretty brilliant, since they have good efficiency at low load + high speed, allowing efficient cruising on flat land despite the motor running at a high fraction of its mechanical rpm limit. A permanent magnet motor geared taller to run at a lower speed is more efficient but the transmission costs more money and needs careful design to not lose efficiency with multiple gears.

[Xist]

EVs have one-speed transmissions?

[Isaac Zachary]

You can't have a magnetism-free electric motor. Wherever there's electricity, there's magnetism, hence why it's called electromagnetism. There are lots of permanent-magnet-free motors already, but they still have electromagnets in them.

[Isaac Zachary]

Originally Posted by Xist

EVs have one-speed transmissions?

Most do. There are a few that have two-speed transmissions.

[freebeard]

IIRC a single-speed drivetrain needs twice the horsepower of one with at least two speeds. Hence the Lexus/Highlander electric axle with 68HP is suitable for a VW Beetle that had 25-40HP.

Conversions that put a motor on the VW transaxle wind up using only two of the gears (maybe reverse?)

Electromagnetism rules:

https://3dwarehouse.sketchup.com/war...6-076f0cea557c

[rmay635703]

Originally Posted by Isaac Zachary

Most do. There are a few that have two-speed transmissions.

Antiques would have a magnet free series wound motor with the 3-5 speed manual intact (normally)

But effiency could be pretty bad at low loads.

[Isaac Zachary]

Porsche uses a two speed transmission in their EV...
https://www.caranddriver.com/news/a2...-transmission/

[serialk11r]

Porsche is one of the only 2 speed EVs on the road. Most are single speed. A more powerful electric motor doesn't really change the low efficiency, but cars use very little energy at low speed so it's not a huge issue. Adding power allows sufficient acceleration with tall gearing.

I don't think you understand the difference between these motors if you interpreted "magnet-free" as "magnetism free".

[Isaac Zachary]

Originally Posted by serialk11r

Porsche is one of the only 2 speed EVs on the road. Most are single speed. A more powerful electric motor doesn't really change the low efficiency, but cars use very little energy at low speed so it's not a huge issue. Adding power allows sufficient acceleration with tall gearing.

I don't think you understand the difference between these motors if you interpreted "magnet-free" as "magnetism free".

Renault has used two speeds in their electric race cars.

https://www.youtube.com/watch?v=42MVi6Fel-E

A "magnet-free" motor is a misnomer. All electric motors have magnets, even if they aren't rare-earth magnets or permanent magnets, they still have magnets.

A reluctance motor has stator poles that are permanent magnets. It also has a ferromagnetic rotor that has magnetic poles induced into it turning it into a magnet too.