Tesla's Breakthru Model 3 Electric Motor

Discussion in 'Tesla' started by Pushmi-Pullyu, Sep 13, 2018.

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  1. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    It's called by the rather unwieldy name PMSRM, meaning "Permanent Magnet Switched Reluctance Motor".

    Clean Technica has an article which takes a longish, deep dive into the tech:

    "Tesla Model 3 Motor — Everything I’ve Been Able To Learn About It (Welcome To The Machine)" by Steve Bakker

    Since I'm not an electrical engineer, I admit my eyes did glaze over a bit in certain sections of the article, but if you're a true Tesla fan then I recommend you stick with it. Even if (like me) you don't get much out of the details of exactly how the PMSRM converts electricity to mechanical rotary force, it's still got some fascinating bits of info. For example:

    ...from Rickard’s continuing comments while still under the car (Rickard, by the way, has gone as far down the Tesla drivetrain rabbit hole as anyone I’ve ever heard of). Extrapolating from EPA documents, Jack is calling the Model 3’s “battery-to-wheels loss” as 6 percentage points more efficient than the Model S (89% of electrical energy is converted to forward motion, compared to 83% for the S).
    Wow! I recall reading that the Tesla Roadster was ~80% efficient in its battery-to-wheel efficiency, and I assumed that would never be significantly improved. After all, gasmobile engineers and auto makers have had over a century to improve the mechanical efficiency of the motorcar, so I assumed Tesla's engineers wouldn't be able to do significantly better. Clearly I was wrong! However, I suspect a bit of that is use of tires with less flex; tire flex is an important contributor to mechanical efficiency loss in a motorcar.

    I think I've also read that Tesla has improved the efficiency of its inverters since the Model S was new, so likely that's also part of why the Model 3 is more energy efficient that the Model S was when it was new.

    It's also interesting, as well as ironic and perhaps a bit sad, that with the PMSRM, Tesla Inc. is moving away from the AC induction motor which Nikola Tesla invented.

    bwilson4web likes this.
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  3. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Is the Wizard of the West now spinning in his grave? And if so, just what sort of reluctance is he emitting? :D

    Nikola Tesla: "The Wizard of the West"

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  4. bwilson4web

    bwilson4web Well-Known Member Subscriber

    My experience is with Prius PM motors and they are documented to be quite different. So I'll withhold judgement until we can find some Model 3 rotors.

    Bob Wilson
  5. interestedinEV

    interestedinEV Well-Known Member

    You are forcing me to recall my days in the physics class. :)
    You are pitting the laws of thermodynamics vs the laws of electromagnetism as far as the conversion of energy. Electro-magnetic energy conversion is always more elegant. Also in ICE, you have one addition factor, conversion of reciprocating motion to rotary motion aka the dreaded word for repairs tranny or transmission. The drive train power loss could be as high as 15%.

    An electric motor provides rotary power where it is needed. While the efficiency of electric motors is high to begin with, there are ways of improving it. Use of better materials, design improvements etc. could move it from about about 93% to say 96% or more, though I am not sure what the current efficiency of EV motors are. (ABB has developed a motor with 99%+ efficiency, but it is not run of the mill). Also, EVs have a lot of electronic parts and other electrical parts and there is scope for improvement. Similarly aero dynamic design can also add to overall efficiency. All these small improvements add up.

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