Tesla’s Chief Motor Engineer Discusses Model 3 Motor Tech

Tesla Model 3 dual motor chassis

SEP 12 2018 BY EVANNEX 30

TALKING MOTORS WITH TESLA’S TOP MOTOR ENGINEER

Tesla is always inclined to do things differently, and this applies to the motors it uses in its vehicles. Most production EVs use some form of permanent magnet traction motor technology, but Tesla’s Model S and Model X both use induction motors. EV engineers have carried on spirited debates about the merits of each technology, and many have speculated about why Tesla chose induction motors from day one.

*This article comes to us courtesy of EVANNEX (which also makes aftermarket Tesla accessories). Authored by Charles Morris. The opinions expressed in these articles are not necessarily our own at InsideEVs.

Above: Charged interviews Tesla’s top motor engineer (Source: Charged)

Christian Ruoff, writing in Charged, tells us that the most likely explanation has to do with historical factors. By many accounts, the reason Tesla started developing an induction motor in the first place is because it inherited the design from AC Propulsion (as described in my history of Tesla). The induction motor used in the Roadster actually had roots going all the way back to GM’s EV1 motor, which was designed by Alan Cocconi. Cocconi based it on existing AC induction motor specs. Tesla initially licensed the design from Cocconi’s company, AC Propulsion. However, Marc Tarpenning later said that Tesla had completely redesigned its induction machine “a year before we were in production…long before we were even into the engineering prototypes.” A lot has changed since those early days in terms of available R&D technology and material costs.

In any case, Tesla’s exclusive use of induction machines has been intriguing to motor experts and EV techies. So, it was particularly interesting in August 2017 when Model 3’s EPA certification application revealed a big change in the powertrain – the document states that Model 3 uses a 3-phase permanent magnet motor.

Tesla rarely offers official comment on technology decisions, so it can be hard to discern the exact engineering thought process. However, when Christian moderated a keynote panel discussion of EV tech experts at the Coil Winding, Insulation & Electrical Manufacturing Exhibition (CWIEME) in Chicago, the panel included Konstantinos Laskaris, Tesla’s Chief Motor Designer, so the Charged publisher had the chance to pry a few more details from the world-class motor engineer.

As usual when interviewing engineers from major automakers, Laskaris wasn’t at liberty to tell us all about the specific quantitative analysis that led to choosing a permanent magnet motor. However, he did offer some interesting insights into the engineering processes the company employed in the analysis.

“It’s well known that permanent magnet machines have the benefit of pre-excitation from the magnets, and therefore you have some efficiency benefit for that,” said Laskaris. “Induction machines have perfect flux regulation and therefore you can optimize your efficiency. Both make sense for variable-speed drive single-gear transmission as the drive units of the cars.

“So, as you know, our Model 3 has a permanent magnet machine now. This is because for the specification of the performance and efficiency, the permanent magnet machine better solved our cost minimization function, and it was optimal for the range and performance target.

Above: The EV technology expert panelists at the CWIEME Chicago event included, from left to right, Jaydip Das – Carpenter Technology Corporation, J. Rhett Mayor – DHX Machines, Konstantinos Laskaris – Tesla, Peter B. Littlewood – Argonne National Laboratory, Tom Prucha – Protean Electric, Matthew Doude – Mississippi State University, and Christian Ruoff – Charged Electric Vehicles Magazine (Source: Charged)

“Quantitatively, the difference is what drives the future of the machine, and it’s a tradeoff between motor cost, range and battery cost that is determining which technology will be used in the future.”

Laskaris later added, “When you have a range target [for example], you can achieve it with battery size and with efficiency, so it’s in combination. When your equilibrium of cost changes, then it directly affects your motor design, so you justify efficiency in a more expensive battery. Your optimization is going to converge on a different motor, maybe a different motor technology. And that’s very interesting.”

If you combine these comments with those made by Laskaris during a 2016 on-stage interview at the CWIEME event in Berlin, you begin to see a clearer picture of the sophisticated process Tesla uses to evaluate different motor designs and optimize them for the specific desired parameters of each vehicle.

“Understanding exactly what you want a motor to do is the number-one thing for optimizing,” said Laskaris. “You need to know the exact constraints – precisely what you’re optimizing for. Once you know that, you can use advanced computer models to evaluate everything with the same objectives. This gives you a panoramic view of how each motor technology will perform. Then you go and pick the best.

“With vehicle design, in general, there is always a blending of desires and limitations. These parameters are related to performance, energy consumption, body design, quality, and costs. All of these metrics are competing with each other in a way. Ideally, you want them to coexist, but given cost constraints, there need to be some compromises. The electric car has additional challenges in that battery energy utilization is a very important consideration.

“This is the beauty of optimization. You can pick among all the options to get the best motor for the constraints. If we model everything properly, you can find the motor with the high-performance 0-60 constraint and the best possible highway efficiency.”

Above: Konstantinos Laskaris, Tesla’s Chief Motor Designer (Source: Charged)

To find answers for these tough engineering questions, Tesla uses sophisticated custom computer simulations that run custom algorithms designed in-house. Before joining Tesla, Laskaris earned a PhD writing the programs that allow computers to more accurately predict how different motor geometries will perform in the real world – a handy skill when you’re trying to evaluate countless motor topologies to find the best.

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Written by: Charles Morris; This article originally appeared in Charged.

*Editor’s Note: EVANNEX, which also sells aftermarket gear for Teslas, has kindly allowed us to share some of its content with our readers, free of charge. Our thanks go out to EVANNEX. Check out the site here.

TESLA MODEL 3

33 photos
2. Tesla Model 3
Range: 310 miles; 136/123 mpg-e. Still maintaining a long waiting list as production ramps up slowly, the new compact Tesla Model 3 sedan is a smaller and cheaper, but no less stylish, alternative, to the fledgling automaker’s popular Model S. This estimate is for a Model 3 with the “optional” (at $9,000) long-range battery, which is as of this writing still the only configuration available. The standard battery, which is expected to become available later in 2018, is estimated to run for 220 miles on a charge. Tesla Model 3 charge port (U.S.) Tesla Model 3 front seats Tesla Model 3 at Atascadero, CA Supercharging station (via Mark F!) Tesla Model 3 Tesla Model 3 The Tesla Model 3 is not hiding anymore! Tesla Model 3 (Image Credit: Tom Moloughney/InsideEVs) Tesla Model 3 Inside the Tesla Model 3 Tesla Model 3 rear seats Tesla Model 3 Road Trip arrives in Tallahassee Tesla Model 3 charges in Tallahassee, trunk open.

TESLA MODEL 3 PERFORMANCE

Tesla Model 3 Performance - Dual Motor Badge
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Tesla Model 3 Performance Tesla Model 3 Performance Tesla Model 3 Performance Tesla Model 3 Performance Tesla Model 3 Performance - Midnight Silver Tarmac Motion Tesla Model 3 Performance - Midnight Silver Tarmac Motion (wallpaper 2,560x – click to enlarge) Tesla Model 3 Performance - White Interior - Wide Tesla Model 3 Performance - White Interior - Touchscreen

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

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EV-A

On the topic of optimising within constraints, I would absolutely love to pick his brain about whether or not letting go of 0-60 times as a constraint would influence range or other parameters, such as charging. If anyone in the know has any answers, I would be grateful.

scottf200

I’m sure it does but certainly then you are not on top of this list: https://insideevs.com/monthly-plug-in-sales-scorecard/

cab

Definitely. One of Tesla’s key attributes is “desirability” and the things that make cars desirable moved well beyond the practical aspects of them decades ago. “Fast” is one of those things that contributes greatly to the Tesla brand image. Even the CEO said something like “At Tesla, we don’t make slow cars”. Indeed, all of my “car guy” buddies and I would not have pulled the trigger on our Model Ses if they had been “slow” or “ugly”.

Joel B

At first I was going to say that the motor would have no influence on charging, but in regards to regenerative braking and one-pedal driving, I suppose it would. From what I understand, some motor designs are better for being able to run as a generator closer to 0 rpm than others. I imagine that would also have a small weight into the motor selection.

I always imagined the switched reluctance motor in the Model 3 to be something of a hybrid between a permanent magnet motor and an induction motor, but I get the feeling that is incorrect. I’d love to learn more about this kind of stuff, so if anyone has some links, please do share.

Matthew Kennel

I think the reluctance machine (motor and generator) in the Tesla 3 rear motor is a hybrid between a permanent magnet synchronous motor and a classic switched reluctance, which has no permanent magnets. BMW i3 motor is roughly similar.

It’s a good solution, using both permanent magnet and reluctance (attraction of soft magnetic materials to magnetic fields) in appropriate places, and less expensive use of permanent magnets than a full pm motor. Most car companies will converge on this for all but the most extreme applications, such as maximum power hypercar with less regard to efficiency. I think the induction motors may handle more power (given a size constraint) but are less efficient (more electrical loss) at lighter loads. I’m not sure, but the front motor in the 3 dual motor might be induction.

The Semi truck will be optimized for highway efficiency, as that means $$$ for its buyers.

Bogdan

This a permanent magnet motor with burried magnets. This way you get a magnetic torque and a reluctance torque out of the motor.
It helps reducing the magnet material which is the most expensive material in the motor and still have all the advantages of a permanent magnet motor.
It is actually a combination between permanent magnet motor and synchronous reluctance motor.
By the way, the NeFeB magnets are on the market since the 90’s, but they are becoming stronger each year. This allows for higher torque and therefore power capacity of the motor which in other words, means efficiency and the asynchronous motor cannot keep up with it.

ffbj

It mainly depends on how a person drives it.

REXisKing

The biggest constraint is more likely to be cost, material cost.
Tesla is good at spending money on R&D.
But, to put something into production, you’ve got to measure unit cost, or profitability.
In other words, the Roadster might get better materials.

Pushmi-Pullyu

“…whether or not letting go of 0-60 times as a constraint would influence range or other parameters, such as charging.”

We need look no farther than the Hyndai Ioniq Electric to see that when a BEV’s engineering is optimized for energy efficiency, it can do noticeably better than the Model 3: I see figures of 4.46 miles/kWh for the Ioniq Electric vs. 3.89 miles/kWh for the LR Model 3 (citation below).

Of course with increase energy efficiency comes longer range, given the same sized battery capacity. And of course that is a tradeoff; the under-powered Ioniq Electric has a vastly inferior 0-60 time, which means it’s not going to be very responsive when you need a burst of speed to accelerate onto a freeway or to pass on a two-lane highway.

I don’t see that charging is going to be affected by the acceleration performance of the EV powertrain, altho a higher performance EV will be able to handle more power going to and from the battery pack, so a lower performance EV might be limited to a lower/slower charging rate. It shouldn’t affect charging efficiency.

https://cleantechnica.com/2018/06/30/what-are-the-most-efficient-electric-cars/

foersom

“So, as you know, our Model 3 has a permanent magnet machine now. This is because for the specification of the performance and efficiency, the permanent magnet machine better solved our cost minimization function, and it was optimal for the range and performance target.”

Performance? On the Tesla model 3 with dual motors, there is only 1 permanent magnet motor, the other is an induction motor. Tesla is cutting cost here.

mskz06

I think Induction motors allow for easier “torque sleep” than pm motors for duel motor applications.

TomArt

well, yeah, because the magnets are always “on”, so to speak.

TomArt

Well, yeah, since the magnets are always “on”, so to speak.

Adam H

They mentioned engineeting vehicles to a price point a number of times. They’re not hiding anything.

arne-nl

“Tesla is cutting cost here”

You make it sound as if building an affordable car is a bad thing.

Pushmi-Pullyu

“Performance? On the Tesla model 3 with dual motors, there is only 1 permanent magnet motor…”

Perhaps he meant “performance” in the broader engineering sense of how well (and how efficiently) a machine performs its intended function, not “performance” in its far more narrow drag-racing sense of straight-line acceleration.

Rusty

A very good discussion on Model 3 motor choices: https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/

TomArt

Yep, that’s the one I read, as well. It’s really fascinating!

Pushmi-Pullyu

Thank you very much for that link!

A fascinating and very informative article, one which every true Tesla fan should read!

veselin

https://www.youtube.com/watch?v=kGFiaWvD-KI
In that video the wheel spins up just like if it is conected to a steper motor.

Shane

In other words, “Batteries have gotten so cheap that we can now afford a less efficient (and less expensive) motor.”

Pushmi-Pullyu

That’s not even remotely the way I read it. In fact, it appears that the Model 3 powertrain is significantly more energy efficient than the Model S/X powertrain. I suspect part of that increased efficiency is a motor which is specifically engineered and tuned for the exact application in question.

Jon

It is the opposite. A PM machine is more expensive to make than induction, but has greater peak efficiency.

Terawatt

Didn’t Tesla publicly state – back when they didn’t use any PM motors – that they used induction motors because it elimiates/dramatically reduces the need for rare earths..? I seem to recall that was part of the marketing blurb for Model S from long before the car saw the light of day.

Pushmi-Pullyu

Quite possibly, back in the day. But now that it’s possible to make strong magnets with relatively little rare earths, the possibilities have opened up for a wider range of uses… including, obviously, in Tesla’s motors.

Bogdan

That’s correct. Back then, in 2008, there was a price surge for the rare earth metalls on the stock market. It cooled off shortly after, but Tesla got stuck with heavy, low efficient induction machines.
Now they are building proper motors for EV. Only the cheapest EVs and Tesla use induction machines. All other EV makers have permanet magnet motors from the begining.

louie

It would seem as though the magnets in a permanent magnet motor would need to be so large and heavy as to be a consideration in the debate about PM vs induction configuration.

Pushmi-Pullyu

Read the article that Rusty linked above:

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

It’s a real eye-opener about the revolutionary rear motor Tesla is using in the Model 3. One of the points it makes is that this new design allows use of much smaller, and therefore far less expensive, permanent magnets. It’s not at all the same type of permanent magnet motor other EV makers are using.

Bogdan

Well, unfortunately you don’t understand electric motor design.
It is exactly the same tech all other EV makers are using.
That’s the reason Tesla doesn’t show the profile of the motor, cause the other manufacturers will say ‘our design is better’.
Having more power doesn’t make it the better motor, it just makes it the more powerfull.

Mister G

GO TESLA GO DESTROY DIRTY GAS GUZZLERS AND DIESELS LOL CONNECT THE DOTS ON CLEAN AIR WAKE UP FOLKS co2.earth