AC Motor With Variable Number Of Poles

AC Motor With Variable Number Of Poles

Hi Tesla,

As you already know, when a regular AC motor is connected to the wheels via a fixed ratio link this configuration will not perform optimally at both low and high speeds. The ratio ends up being optimized for mid-range speed resulting in reduced low and high speed performance. One way around this problem is to have a variable gear ratio via a mechanical transmission, or achieve a similar result using a motor with variable number of poles.

I have been working on a design that can be electronically configured on-the-fly to operate in 4, 2 or 1 pole-pair mode, making it very suitable for fixed ratio application at both low and high speeds. I believe this design is very well suited for EV application and I thought you might want to have a look at it. Please provide a contact email and I will send you more information.

Thank you.

eberhard | March 24, 2011

Hi marcuac,

i talked recently to JB Straubel in Milan regarding this subject. My idea was to used two smaller motors with multipoles as an direct drive without gearbox and differential. This configurations would allow vector torquing as well. JB Straubel told me, that they skipped this idea because of weight and efficiency reason. The new ac-motor for model s will even spin faster allowing an higher gearbox ratio.



marcuac | March 24, 2011

Hi Eberhard,

I'm sure someone did or will implement the setup you suggest and it should work very well. I don't think it should increase the weight but it does add complexity on the electronics side, almost doubling up, though using half-duty power components.

My design is a single motor that can directly replace their own in the same setup. The motor can run in 4 pole-pair (x 2 x 3-phase = 24 individual poles) configuration at low speed, switch to 2 pole-pairs for intermediate speed and then to 1 pole-pair for top speed. The result is similar to having a 3-speed transmission, except it's achieved without any mechanical means. This operation is enabled simply through winding and electronics design with minimal added complexity.


searcher | March 24, 2011

marcuac, Like you effort at trying to be an innovator. Sounds like you are prety well steeped in the technology. I have a controversial concept conerning the wheels of the car. If you have a few minutes will you go to "Esoteic EV Ramblings" and crituqe the idea. I have a feeling some tesla like technology could be incorporated to facillitate this. Know what the devices, {yet undeveloped} need to do just how do we get them to do this.I keep getting a lot of flack about perpetual motion but I don't concede this just yet. So being of an innovative bent of mind just pop over and check it out. Many thanks.

Brian H | March 26, 2011

Variable Poles? What about Czechs? Or Swedes? Aren't they moody enough?

VolkerP | March 28, 2011

Czechs were counted out because they are a fission product of Czecho-Slovakians. They claim to now have reached a stable state but investors shuddered away.

Swedes cannot be kept in the same motor encasing with Norwegians. Both are said to lack performance under hot climate conditions but that is an evil-minded rumor, of course.

Experiments with Germans looked promising but nobody wanted a motor driven by "germs".

Brian H | March 28, 2011

Maybe not Germ-mans, but how 'bout Germ-wimmens?

At least none of them are Franco-phonies.

searcher | March 29, 2011

Hi marcuac, don't be upset this is just initiation,hang in. Some funny duds {oh sorry,dudes} on this site.

douglas_b_o | January 25, 2016

Hello marcuac,

I'm a Power Electronics researcher, and I've just came to the same problem/solution regarding variable number of poles. I beleive that this kind of motor can be the "defacto" motor for automotive application.

Please, tell me how I can contact you, so we can discuss this idea.
My e-mail is

I'm waiting for one answer.


Best regards.

milesbb | January 26, 2016

Nothing new or technically difficult about switching poles to change motor speed. Unfortunately the horsepower at the higher pole configuaration (lower speed) is significantly reduced, generally 25% of the high speed configuaration when going from a 2 pole to a 4 pole motor.