Tesla’s Chief Motor Engineer Discusses Model 3 Motor

Tesla Model 3 dual motor chassis

MAR 13 2018 BY STEVEN LOVEDAY 11

Red Tesla Model 3 at handover event

Tesla Model 3 at the July 2017 handover event

Tesla’s Chief Motor Designer, Konstantinos Laskaris speaks to the 3-phase permanent magnet motor technology used in the Model 3.

Most EVs use permanent magnet motors. However, Tesla uses induction motor technology in its Model S and X, as it did in the first-gen Roadster. This has always been something that has generated quite a bit of conversation, especially among engineers and those “in the know.” Interestingly, the automaker changed gears for its Model 3, choosing to go with the permanent magnet technology.

ALSO READ: Tesla Model 3 Gets 80.5 kWh Battery, 258 HP, According To EPA Document

According to ChargedEVs, the main reason Tesla has always relied on the induction motor is that the technology for it was already developed by AC Propulsion. GM’s EV1 motor was also based on the same tech, which Tesla actually licensed from the designer for use in the Roadster. However, later the Silicon Valley company completely redesigned the Roadster’s motor.

Long Range Tesla Model 3 (single-motor chassis)

Long Range Tesla Model 3 (single-motor, rear-wheel drive)

With all of the history involved, one could only assume that Tesla would continue on the same path with the Model 3, but EPA documents revealed otherwise. Though the automaker is essentially unwilling to provide many specifics about the new motor tech, ChargedEVs had an opportunity to discuss it with Laskaris at a recent exhibition.

We’ve included the key takeaways from the interview transcript below. To read the entire comments, follow the link at the bottom of the page:

  • The permanent magnet machine for the Model 3 made the most sense due to performance, efficiency, and cost minimization
  • The future of Tesla’s motor choices will be determined by working with a target range and efficiency, which may mean a less expensive motor paired with a more expensive battery or vice versa
  • In order to optimize a motor, you need to know exactly what you expect it to do and what its constraints are. Then, computer models can be used to evaluate how it will actually perform.
  • Highly advanced computer simulations using custom algorithms succeed in coming up with the best possible powertrain combinations within the automaker’s constraints.
  • In the end, parameters including “performance, energy consumption, body design, quality, and costs” all weigh in to find the best balance between “desires and limitations.”
  • The best motor should provide a welcome balance of “high-performance 0-60 constraint” and “the best possible highway efficiency.”

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Source: Charged EVs

Categories: Tesla

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11 Comments on "Tesla’s Chief Motor Engineer Discusses Model 3 Motor"

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Paul Stoller

Here is another article that goes in depth (be it speculative) about how they think Tesla designed the Model 3 motor. It’s quite an interesting read.

https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/

Marcel

There’s a much better article on the Model 3 motor here: https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/

There is some speculation in the linked article, but it looks like their conclusions are solid.

“Tesla calls it a PMSRM, Permanent Magnet Switched Reluctance Motor. It’s a new type, and very hard to get right, but Tesla did it!”

Even though it’s using permanent magnets, it’s (probably) a new type of motor, which the article above doesn’t mention.

Doggydogworld

Switched reluctance isn’t a new type of motor. Old articles about different types of EV motors almost always discuss it. It just hasn’t been used in EVs much due to control issues. Motor control is a Tesla strength.

Engineer

By “switched reluctance”, they likely really mean interior permanent magnet machine, which is the same as on most existing EVs. Nothing ground breaking here.

While the cost of a PM machine is usually higher, so is peak efficiency. From a vehicle standpoint, it is cheaper than a higher capacity battery to achieve a given range.

Pushmi-Pullyu

One factor missing from this article is that strong permanent magnets have come down in price quite a bit recently, with new techniques for making them with reduced use of expensive rare-earth elements.

Surely that is at least one of the factors affecting Tesla’s decision to switch to permanent magnet motors, and possibly the most important one.

Toyota is also getting ready to start using motors with cheaper permanent magnets:

http://www.autonews.com/article/20180220/COPY01/302209964/toyota-readies-cheaper-ev-motors-by-halving-rare-earth-metal-use

Chris Stork

As I understand it (based on the Clean Technica article everyone is referencing), it does use permanent magnets, but not nearly as many as a conventional PM motor as we think of it; it uses fewer/smaller magnets to level out the “torque ripple,” but is otherwise more like an induction motor than a PM motor.

But the big question on my mind is: will they ever offer a retrofit for existing Model S/X cars? You just need to unscrew 20 bolts and use a special scissor-jack lift to remove the entire S/X power train (at least the rear one. The front with steering couplings is probably not as simple), so it seems feasible they, or a third-party aftermarket, could create a swap-in replacement. And of course the software/firmware would need to be updated.

I’m also looking forward to a more in-depth explanation about how they’re using the motor to generate heat by running it less efficiently (but still more efficiently overall than having a separate resistance heater).

Bill Howland

Yup, more gobbledygook explanations to make something 20th Century seem 21st.

Tesla was dead last amoungst manufacturers to not use a 19th century design.

Induction motors are fine in most applications where they are cost effective, but automotive applications have always the issue that the electricity is VERY EXPENSIVE. If you can have a motor that is 5% more efficient you need 5% less of everything else. Plus there are no cooling requirements for that part of the motor which doesn’t manufacture any heat in the first place.

Get Real

Yup, more innovation from Tesla so welcome to the 21st Century.

Tesla solved the problem of torque ripple on switched reluctance motors and now have a motor that both costs less and is highly efficient (making the sporty Model 3 more efficient then every other EV except the not sporty Ioniq.

This validates the German teardown of the Model 3 where they were stunned at how excellent, efficient and relatively low cost the drivetrain/power electronics are.

ModernMarvelFan
It isn’t really that new. Reluctance motors are the cheapest type of motors there is. But since it isn’t smooth (thinking of spinning a step motor by hand to feel the poles), it isn’t ideal for EV application. Adding some PM in between the poles to smooth out the torque curves is a small evolution of typical engineering design. Traditionally, if application requires smooth and efficient operation, engineers would just go to PM synchronous motors. The reason that Tesla is trying to use reluctance motor combined with magnet is trying to save cost (Model 3 margins must be thin) and it is a bit better on press since the less PM it uses, the less argument against its cars as potential source of pollution due to NID magnets and its sometimes questionable supply chains. What I don’t agree is that everyone claims that EV motors are so cheap to make, then why does Tesla need to squeeze more out of the cost since the difference is very small at mass scale. They must have done it to minimize NID magnets. I also heard the rumors that in D version of the model 3, the front motors will use Induction motor,… Read more »
Bill Howland

GET REAL:

Nope, induction motors are cheaper.

An additional sleight of hand here is to posit that there is such a thing as “AC PM motors” and “DC PM motors” when they are the same, or put another way, there is more variation within the category than from without.

B. Amin

It is claimed in this article that using permanent magnets in switched reluctance motors causes additionnal torque for the motor which sounds celarly erroneous: This would mean that for very low phase current, and ultimatly zero phase curent, the motor could still develop some torque!
The benefit of using PM could be the improvement of the Volt-Ampere of the Power Supply, but this could also be achieved without using permanent magnets.
The reduction of the torque ripples using permanent magnets appears also very dubtious. Actualy à well designed SRM ( without PM) exhibits less than 10% torque ripples.