Model 3

Might the Model 3 use a different motor technology?

edited November -1 in Model 3
I noticed an article come across my news feed claiming a Chinese company has signed a deal to supply permanent magnets to Tesla.

Another article on the Rare Earth Elements market states, " is argued that Tesla Motors will move to replace their AC induction motor, which does not use REEs, to a permanent magnet motor that requires rare earth permanent magnets. Although cheaper, the AC induction motor is larger, heavier, and less efficient resulting in more draw on the lithium ion battery pack, when compared to a permanent rare earth magnet motor." --

Also, on October 11, 2015, JB Straubel told an audience at the University of Nevada, Reno, "We’re inventing a whole new platform: it’s a new battery architecture, it’s a new motor technology — brand new vehicle structure..."

These three datapoints could signal a change in the Tesla powertrain for the Model 3.


  • edited November -1
    Sure looks like they're updating it.
  • edited November 2016
    They definitely redesigned the inverters. Tesla claimed a big leap in efficiency.
  • edited November -1
    Correct me if I am wrong, but doesn't China control most if not all rare earth material, which just begs the question, why would you build a motor based on a material that is controlled by 1 source?
  • edited November -1
    It doesn't state what the magnet is for - could be the speakers!

    There are over 60 motors, some of which likely use various magnet types.

    Very doubtful they are going to switch the main motor to a DC motor. Few advantages and lots of disadvantages.
  • edited November 2016
    "but doesn't China control most if not all rare earth material,"

    No, unless you mean by 'control', produce enough at a lower price than anyone else, making other sources wait until the market improves. They can't embargo or inflate the price without losing that 'control'.

    "Rare earth" material encompasses a lot of different elements, each with their own availability and extraction, and refining costs.

    Thank you kindly.
  • edited November -1 said "Very doubtful they are going to switch the main motor to a DC motor. Few advantages and lots of disadvantages"

    Thanx for that link. It does appear though that when JB stated "We’re inventing a whole new platform: it’s a new battery architecture, it’s a new motor technology" that he was referring to the drive motor. Still, "new motor technology" does not in and of itself mean rare earth magnets. But it's a hell of a comment when coupled with the rare earth magnet news.

    As a point of interest, in my limited experience researching the current Tesla motor it does seem they could switch to a permanent magnet without going to DC. Keep in mind that AC power is used in two places on the motor; To excite the (stationary) stator ... and two induce a current flow on the (spinning) rotor.

    If they switched to a permanent magnet on the rotor that would eliminate the battery power required to invert the DC to AC in order to induce an opposing magnet field on the rotor. The magnetic field would simply pre-exist.

    You would still need to excite the stator though, and that could still be done by inverting DC to 3-phase AC (as opposed to pulsing DC current) as they are doing now. It's funny though, because if they went that route the motor would no longer be a Nikolai Tesla *induction* motor.

    Just another brick in the wall when it comes to speculating what our Model 3's will be like. Thanx to the OP for posting all the great links.

  • edited November 2016

    One thing to keep in mind too is that the link referred to China losing a World Trade Organization decision regarding quotas. From the article:

    "The Chinese system of export quotas and taxes was scrapped in 2015 after China lost an appeal with the WTO"

  • edited November -1
    Here is an excellent (and fairly technical) blog on DC vs AC motors for EVs.

    Basically, DC motors with magnets are more efficient than AC motors at low power levels, and make the most sense with Hybrids and low powered EVs. AC motors become more efficient on average than DC motors (and usually cost less) for higher power applications like Tesla's vehicles.

    AC inverters are far more complex to design than systems that power DC motors, but this is a one-time cost. If you have a limited design staff, then DC motors are the way to go if you need to get the project done quickly.

    So unless Tesla is going to start making EV golf carts, I expect they will stay with AC motors.
  • edited November 2016
    Tesla electric vehicle will use permanent magnet motor

    Google translated:

    Tesla electric vehicle will use permanent magnet motor to adept to the market.

    2016/11/4 8:58:13

    As the "Big Brother" of the new energy automotive industry every of Tesla's move is of public concern. Recently, Tesla purchased NdFeB magnets for its electric vehicle drive motor. Teslar signaled to convey to the outside world by beginning to give up sticking blindly to the induction motor drive line and began entering the current field of new energy with the most widely used rare earth permanent magnet direct current motor.

    the use of an electric vehicle direct drive motor, previously Nicolas Tesla himself has invented one, as a three-phase induction motor (asynchronous motor), which can tolerate significant changes in operating temperature, the output torque of the induction motor can be adjusted over a wide range, is at high-speed of good efficiency and low cost, but the asynchronous induction motor due to unilateral excitation the current energy required to produce the unit torque is high and so energy consumption is bigger...the induction motor is limiting vehicle performance.
    Therefore, the choice of a permanent magnet motor is more sensible and in line with market needs. The same applies to Tesla, for which it is also true to be committed to building the best electric vehicles.

    In order to fit the general needs of the Chinese market, Tesla began walking on two legs:
    One is the new development of a rare earth permanent magnet drive line especially for the Chinese market, the other is to take the high-end positioning in the road of pure electric vehicles.
  • edited November -1
    The things I have read seem to state that permanent magnet synchronous motors have the efficiency edge due to less magnetic slip between the stator and armature fields. They also seem to have higher torque density.

    This article describes an axial flux induction motor for EV use. Also looks interesting, though it seems to be a marketing piece. In the midst of describing the AFIM strengths, it does state that, "[permanent magnet motors] can be made to be quite efficient at relatively low torque level and intermediate speed." Considering that is the mode where our cars spend most of their time, this may be a strong point.

    Also, the ability to have a high pole count also enables the use of variable pole counts. Reducing the active number of poles can increase motor speed at lower inverter frequencies. As I understand it, this could give some of the benefits of a transmission (better performance at high speed) at the cost of a more complex drive circuit.

    Fun speculation. :)
  • edited November -1
    Perhaps a dual-motor tradeoff - imagine a PM front motor and an AC Induction rear motor. The car could transition from one to the other or both depending on what the present need was - acceleration or cruise, low speed or high speed, etc.
  • Yep. Just because magnets are in there doesn't mean it's DC. ;)
    This style motor also continues regen to much lower speed.. Could be a good move. But yes, naturally now we are looking at rare earth magnet availability.
  • edited November 2016
    Article seems like conjecture to me, and while possible, seems very unlikely. It makes statements sound like fact, when no one is quoted from Tesla, and Tesla itself has never hinted at switching to a DC main motor. AC motors are more efficient at higher power levels - similar to what Tesla uses. I can see using a DC motor in golf carts and low-end EVs that don't offer much power, where DC motors are more efficient. Fun to see what appears - we should know in another 9 months.
  • Electric drag race cars use DC motors, the torque is insane.
    But I don't think they will go this route because then we would have brushes and commutators, wear items that can go bad. And need to be precisely adjusted.
  • edited November 2016
    Tesla has a culture of continuous improvement and hopefully this continues so they never get locked in to any one techlogoly. The legacy car makers did that and just look at the mess they are in! Make the motor last a million miles ... that's what I want ... the torque is pretty good as is ;)
  • edited November 2016
    dave -
    I don't know why electric drag racers would use brushed DC motors; perhaps it's easier to drive insane amounts of current through the motor that way.

    I'd assume Tesla would use a brushless DC motor. The big difference: brushed DC motors put the wire coils on the rotating portion of the motor and the magnets on the stationary portion, where brushless puts the magnets on the rotating portion and the wire coils on the stationary portion. Brushless DC motors would have the same longevity and freedom from maintenance as an AC Inductance motor.
  • Frank, the type I'm talking about are similar to what's in a forklift. The power is much higher because both the rotor and stator are electromagnets, meaning we can set up a strong field at zero rpm and it can be stronger than natural magnets. Practically saturate the iron for all it's worth, maximum field density. AC induction motor has to induce the magnetic field which likes a little bit of rpm.. why using magnets in some type of hybrid motor would be pretty cool to help out the bottom end. It's efficient but DC motor is king for brute force. But of course there are tradeoffs, and it's the brushes. Not only do they wear but there is also tradoffs/priorities made in aligning the brushes. Much like a cam shaft in a car, do you optimize for low end or high end?

    A few hours on wiki can teach you a lot.. when people get the itch to soup these up it'll get very interesting. :)
  • edited November -1
    Doubt it would be ready for the 3, but could Tesla be working on a switched reluctance motor?

    No magnets, but theoretically much more efficient if you could get it to work.
  • edited November 2016
    Dave -
    I wasn't familiar with that concept for a motor, but it makes a lot of sense in not being limited by the field of a permanent magnet. Thanks.
  • edited November 2016
    @dave:"meaning we can set up a strong field at zero rpm and it can be stronger than natural magnets. "

    Are we of the impression that the torque at zero rpms is lacking? You people want to rip the tread off the tires?

    Thank you kindly.
  • edited November -1
    Speculating along an entirely different line... perhaps Tesla Motors has perfected the Em drive.

    (bear in mind that a body of knowledge exists nullifying Newtonian Mechanics)
  • edited November 2016
    Wow. Again? God.
  • @topher go to youtube and look up the "white zombie" electric drag race car. :)
  • edited November -1
    Electric drag racers typically do not care about longevity or cost - two concerns when producing a high volume production vehicle. Drag racers also do not have the engineering team to design a suitable AC inverter. The Tesla team took years to design a suitable inverter for the Roadster, later enhanced for the Model S and X. . It may also be the prime reason most low power EVs use DC motors - it is fairly easy to design, and if you just need a compliance vehicle, why bother to do the tough engineering work or worry about the need for high volume rare earth magnets.
  • edited November 2016
    TeslaTap: +21! Exactly.
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