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Motor cooling (out of main)

Artful Dodger

"Ducimus, lit"
Aug 9, 2018
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Canada
With all the attention to the Plaid, a halfway decent Raven time would hopefully put an end to the "Model S overheats and goes into limp mode" narrative and therefore be a big win in itself. Applying to a car available now, not 12 months out.
Raven ships with a rear AC induction motor, which will overheat. It is the nature of the design, because there's no way to cool the copper windings on the internal rotor.

Wishfull thinking doesn't change the physiks, but Plaid does because SRPM motors do not have rotors that overheat. They don't have any copper windings on those rotors, which are just pieces of plain steel, not even with permanent magnets, which are on the external stator. That's why the Plaid prototypes don't need to roll back power when driven hard.

It might be helpful if you studied about the motor designs. Jus' sayin'. Raven will overheat when driven hard at the 'ring.
 

mongo

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May 3, 2017
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Raven ships with a rear AC induction motor, which will overheat. It is the nature of the design, because there's no way to cool the copper windings on the internal rotor.

...

It might be helpful if you studied about the motor designs. Jus' sayin'. Raven will overheat when driven hard at the 'ring.

The Tesla AC rotor is liquid cooled via coaxial tube on the end opposite the output gear. Also (pedanticly) it's not really windings (multiple turns), it's a shorted squirrel cage (single turn).
 
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Artful Dodger

"Ducimus, lit"
Aug 9, 2018
8,482
104,470
Canada
The Tesla AC rotor is liquid cooled via coaxial tube on the end opposite the output gear. Also (pedanticly) it's not really windings (multiple turns), it's a shorted squirrel cage (single turn).
Yes, which is why it overheats. The copper in the rotor can not be adequately cooled to shed the approx. 80 kw of heat its producing at full power. Please stop confusing the uninitiated. Please amend your comment to include the plain, easy-for-laymen to understand fact that Raven will overheat when driven hard at the 'ring. Thank-you.
 
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StealthP3D

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Dec 12, 2018
8,797
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Maple Falls, WA
Raven ships with a rear AC induction motor, which will overheat. It is the nature of the design, because there's no way to cool the copper windings on the internal rotor.

There are some EV's that send coolant through the rotor. However, this increases complexity by adding shaft seals to retain the coolant. This is a lot like the oil seals on the ends of the crankshaft on an ICE engine. Except that Tesla motors spin up to around 19,000 rpm's which might be hard on any seal design. And coolant is more difficult to retain than oil. Shaft seals on a high rpm motor also add another source of constant friction, reducing efficiency and range.
 

mongo

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May 3, 2017
12,904
38,113
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Yes, which is why it overheats. The copper in the rotor can not be adequately cooled to shed the approx. 80 kw of heat its producing at full power. Please stop confusing the uninitiated. Please amend your comment to include the plain, easy-for-laymen to understand fact that Raven will overheat when driven hard at the 'ring. Thank-you.
Umm, no? All motors can overheat, not that I said anything about overheating either way, I was correcting your error:
It is the nature of the design, because there's no way to cool the copper windings on the internal rotor.
Which is totally false and requires (in my mind) addressing when one says things in the same post like:

It might be helpful if you studied about the motor designs. Jus' sayin'.
The Tesla AC motor is actively cooled, and does not have windings (as an average person would imagine them) rather solid bars connecting two shorting rings.
Squirrel-cage rotor - Wikipedia

Further:
@mongo See what happens?
The post you quoted was made before my post (replying to yours) and has nothing to do with me. If you do not want to explain things to people so that they can understand, then don't. Either way, do not post incorrect information in the name of simplicity.

From Elon himself :
The bigger challenge is cooling it effectively, particularly cooling the rotor, because you’ve got this rotor going at 18,000 rpm. In the Model S, we coaxially cool the rotor in order to have high steady state. Also for an electric motor, it’s easy to get peak power for a short period of time – it’s hard to have sustained peak power, because you overheat, and it’s hard to get high efficiency over a complicated drive cycle. Those tend to be the problems we wrestle with.
Charged EVs | Elon Musk: Cooling, not power-to-weight ratio, is the challenge with AC induction motors

The rotor is cooled, and yes, it is not infinitely cooled.

There are some EV's that send coolant through the rotor. However, this increases complexity by adding shaft seals to retain the coolant. This is a lot like the oil seals on the ends of the crankshaft on an ICE engine. Except that Tesla motors spin up to around 19,000 rpm's which might be hard on any seal design. And coolant is more difficult to retain than oil. Shaft seals on a high rpm motor also add another source of constant friction, reducing efficiency and range.

Yes, some EVs, like Tesla
(now who is confusing people?)
o_O
 

mongo

Well-Known Member
May 3, 2017
12,904
38,113
Michigan
Are you saying Tesla sends coolant through the rotors? That is not my interpretation of Musk's comments. I believe he was referring to the rotor being cooled by air as it spins around.

It is indeed coaxially liquid cooled. I can find more refernces, if needed. Just look at the hollow end of the motor...

coolRotor.PNG
 

StealthP3D

Well-Known Member
Dec 12, 2018
8,797
65,136
Maple Falls, WA
It is indeed coaxially liquid cooled. I can find more refernces, if needed. Just look at the hollow end of the motor...

View attachment 456323

I'm not seeing any seals to retain the coolant. Regardless, there is only so much surface area in a rotor shaft. Some EV's actually pump the coolant into the rotor itself (more surface area) using a coolant pump. Of course, that requires shaft seals.
 
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mongo

Well-Known Member
May 3, 2017
12,904
38,113
Michigan
I'm not seeing any seals to retain the coolant. Regardless, there is only so much surface area in a rotor shaft. Some EV's actually pump the coolant into the rotor itself (more surface area) using a coolant pump. Of course, that requires shaft seals.

It's a simplified view.

Here is a good post from the thread in 2012 on the motor cooling.
Model S motor
 

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