[wladius]

Hi,

I'm reading into the EV topic (I'm no mechanic or electrical engineer, I just like to learn stuff) and there's one thing I don't understand.

From what I've read, the rear motor of Tesla can output from 285kW to 350kW of power, depending on the model. And that motor weights about 31 kilograms.

But when I take a look and AC induction motors from other manufacturers, they are nowhere close to those numbers.

In the evwest catalog, most motors from are several times as heavy, providing just fraction of power. For example the "AM Racing AMR Dual Stack 250-90 AC Motor - Liquid Cooled, Permanent Magnet - Remy" can provide similar power, but weights over 2.5 as much as the Tesla motor.

So my question is - do I understand those parameters incorrectly, am I looking at wrong motors/sources, or is Tesla's technology simply that effective and "cutting edge"?

Thanks for the clarification

 

[Kevin Sharpe]

From what I've read, the rear motor of Tesla can output from 285kW to 350kW of power, depending on the model. And that motor weights about 31 kilograms.

The Tesla Model S/X 'small' front and 'small' rear drive units weigh ~90kg and produce ~220kW/~300HP peak.

The Tesla Model S/X 'large' rear drive units come in three different versions ranging from ~330kW/~450HP to ~480kW/~650HP peak. All versions weigh ~130kg.

afaik we don't yet have any reliable figures for the Tesla Model 3 drive units.

You can see the 'small' front and 'large' rear drive units in this video;

 

[brian_]

So my question is - do I understand those parameters incorrectly, am I looking at wrong motors/sources, or is Tesla's technology simply that effective and "cutting edge"?

When specs are tossed around, the difference between continuous and peak power is often skipped. If you compare peak Tesla power to continuous power for another brand, you'll see this sort of discrepancy.

Tesla motor technology is not exceptional, although they do use conventional induction motors, while other production EVs use permanent magnet synchronous motors. Model S/X motor technology is so old that they're not even using it for the Model 3, which has PM motors.

 

[Duncan]

To expand on Kevin's post

The Tesla Model S/X 'small' front and 'small' rear drive units weigh ~90kg and produce ~220kW/~300HP peak.

That is the drive unit - it includes the reduction gearing, the diff and the inverter - 31Kg for the actual motor sounds about right looking at it

 

[lastcyrol]

To expand on Kevin's post

The Tesla Model S/X 'small' front and 'small' rear drive units weigh ~90kg and produce ~220kW/~300HP peak.

That is the drive unit - it includes the reduction gearing, the diff and the inverter - 31Kg for the actual motor sounds about right looking at it

It doesn't sound right to me. But it is strange how the value 31 came up. If I were to make an estimation I would use good round numbers like 30 or 40.

Anyway. In that assembly, I would expect the controller to weight not more than 20 kg., and even that seems too much for me. The reduction gearbox in that case would have to weight the remaining 40 kg. (39 to keep up with the exact number for the motor) . But this seems way too much for just one stage transmission. A normal five-speed manual transmission (for FWD) would weight about the same, and that one would have five times more gears plus the reverse.

Has anyone ever disassembled a Tesla drive-train and measured the motor?

 

[Kevin Sharpe]

Has anyone ever disassembled a Tesla drive-train and measured the motor?

IHS did a complete Model S teardown if you have a subscription (here).

Failing that, I can confirm the inverter for the 'small' rear drive unit weighs ~6.5kg (note that inverter in photo is missing the controller PCB).

 

[Duncan]

It doesn't sound right to me. But it is strange how the value 31 came up. If I were to make an estimation I would use good round numbers like 30 or 40.

Anyway. In that assembly, I would expect the controller to weight not more than 20 kg., and even that seems to much for me. The reduction gearbox in that case would have to weight the remaining 40 kg. (39 to keep up with the exact number for the motor) . But this seems way too much for just one stage transmission. A normal five-speed manual transmission (for FWD) would weight about the same, and that one would have five times more gears plus the reverse.

Has anyone ever disassembled a Tesla drive-train and measured the motor?

You forgot about the diff - and you do need a bit of metal to handle those power/torque numbers
Comparing the reduction gear for 300 Hp to the gearbox for a 100 hp FWD car is a bit thin

 

[lastcyrol]

I could argue about the need for massive transmission to handle high power. My understanding is, that mass is needed for handling high torque. With high rpm you kind of get the power for free. But I choose not to argue, because for whatever reason you could be perfectly right. I just wanted to share my doubts.

I couldn't watch the complete Model S teardown from the link, as I have no subscription, but I searched online and the closest I got was a statement from Musk, that the motor (no mentioning which one) alone was 70 lbs. This is where the number 31 seems to have come from. An other place was giving the number 350 lbs. for the "electric motor + inverter" and another 175 lbs. on the differential alone, that for Model S, but again not specifying which version.

The image of the inverter from the small drivetrain on the scale that you Duncan shared is something that no one could doubt, unless somebody is to notice that there is a writing on the scale that says "Max 5000g" on the left under the display, which reads 5979 g.

 

[brian_]

I could argue about the need for massive transmission to handle high power. My understanding is, that mass is needed for handling high torque. With high rpm you kind of get the power for free.

The high motor speed means that the small gear on the motor shaft doesn't handle much torque... but the high reduction ratio means that gear which it drives is large... and handling a lot of torque. That stage is followed by the final drive reduction, with wide gears to handle the forces there. Whatever the motor speed, the end result at axle speed is high torque, so components need to be robust. I'm not surprised that these components are hefty.

An other place was giving the number 350 lbs. for the "electric motor + inverter" and another 175 lbs. on the differential alone...

That would be 175 pounds for the transmission and differential... but the 350 pound weight for the motor and inverter appears to be nonsense. Perhaps it is the weight of the entire drive unit (inverter, motor, reduction gears, differential, case) in the case of the higher-power rear unit?

 

[Kevin Sharpe]

The image of the inverter from the small drivetrain on the scale that you Duncan shared is something that no one could doubt, unless somebody is to notice that there is a writing on the scale that says "Max 5000g" on the left under the display, which reads 5979 g.

You got me, I spent all day fabricating that image but missed the label on the scales... oh, its Kevin BTW

 

[Kevin Sharpe]

Theses two EVTV videos are useful if you want to see what's inside the large Tesla drive unit

 

[lastcyrol]

You got me, I spent all day fabricating that image but missed the label on the scales... oh, its Kevin BTW

Kevin,
Please accept my sincere apology. I obviously was not paying attention to whom I was answering and who uploaded the pictures.

And i didn't mean to say the image was fabricated, but that the scale is overloaded, and probably the measured weight would be different on a scale that could carry, say 10 kg. But still, the image gives a good approximation on the inverter weight, so that one doesn't need to speculate about it.

 

[sjd.aliyan]

One other thing tesla induction motor uses copper rotor which increases efficiency and power output.

https://www.youtube.com/watch?v=4OddRX9uO4o

there is also a video that elon explains how this motor can produce such power.

 

[brian_]

One other thing tesla induction motor uses copper rotor which increases efficiency and power output.

Compared to what... an aluminum squirrel cage? Sure, I can believe that copper is better, but it's not exceptional in any way. Both copper and aluminum are routinely used in induction motors.

https://www.youtube.com/watch?v=4OddRX9uO4o

there is also a video that elon explains how this motor can produce such power.

I'll save other readers a couple of minutes: there's no technical information in the sales video, other than that the motor has a copper-bar rotor.

That's one antique video! It actually shows a prototype, from before production introduction (although that doesn't matter in this case because nothing substantial has changed in the Model S since then). The on-screen caption which says "copper rotor inside" is pointing to the wrong place: it points to the inverter, not the motor. I always thought that Tesla made the inverter housing cylindrical to give the illusion of two motors (and of all motor, no electronics), and in this case it appears to have worked.

 

[sjd.aliyan]

Compared to what... an aluminum squirrel cage? Sure, I can believe that aluminum is better, but it's not exceptional in any way. Both copper and aluminum are routinely used in induction motors.


I'll save other readers a couple of minutes: there's no technical information in the sales video, other than that the motor has a copper-bar rotor.

That's one antique video! It's actually shows a prototype, from before production introduction (although that doesn't matter in this case because nothing substantial has changed in the Model S since then). The on-screen caption which says "copper rotor inside" is pointing to the wrong place: it points to the inverter, not the motor. I always thought that Tesla made the inverter housing cylindrical to give the illusion of two motors (and of all motor, no electronics), and in this case it appears to have worked.

ok you are the best of us.
Now you are happy?

 

[brian_]

...https://www.youtube.com/watch?v=4OddRX9uO4o

there is also a video that elon explains how this motor can produce such power.

Also, the guy in the video is identified as Ted Merendino (a Tesla Product Planner), not Elon Musk. Not everything from Tesla is from Elon.