But what are the heat losses to the environment when it is cold? I've seen that a model S can't even keep the battery warm under normal driving conditions and that regen and charging get limited when it is really cold.
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PMAC vs induction motor for model 3
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But what are the heat losses to the environment when it is cold? I've seen that a model S can't even keep the battery warm under normal driving conditions and that regen and charging get limited when it is really cold.
I agree, and when there is not enough waste heat the model S/X has a 6kW cabin heater and a 6kW battery heater it can activate.
In case someone is interested in the thermal management system in Model S/X:
Tesla Thermal Management System - explanation
Why does Tesla use a Resistance Heater instead of Heat Pump
(see examples here when ambient temp are below freezing, summer temps, supercharging etc).
SageBrush
REJECT Fascism
That is interesting -- thanks.
So it sounds like Tesla would have to keep the heat from escaping to the environment if they want to collect it for other uses during the winter.
SageBrush
REJECT Fascism
If Tesla can reduce heating requirements sourced from the battery by half in the winter, that would be great.
JRP3
Hyperactive Member
Don't forget the pack needs to be kept warm in cold weather as well, so some or all of that 2kW of waste heat is already used.
Although the patent Karen quoted above shows Tesla was thinking about it a while ago, I've seen no reason to expect that the battery/motor coolant will be able to heat the cabin in the 3.
More importantly, as someone with a fair amount of cold weather driving experience in the X, I echo the other comment - in my X, the car clearly puts a fair amount of energy into just keeping the pack warm, and a bunch more into keeping the cabin warm when the temperatures dip well below freezing.
Maybe (hopefully) the 3 will have much better insulation, but from the S/X experience, we'll be lucky if the natural powertrain waste is enough to keep the battery pack warm in sub-freezing conditions in typical driving.
SageBrush
REJECT Fascism
There is a part of me amused by concurrent threads, one trying to imagine ways to cool off the battery to aid fast charging, and the other one hoping for better battery insulation to keep it warm.
The Tesla engineers must walk around with splitting headaches.
This is why Engineering is still as much art as science... All about choosing the right combination of tradeoffs and finding ways to compensate for the weaknesses inherent to your chosen approach while maximizing the strengths.
omgwtfbyobbq
Active Member
Here's a recent patent from Tesla on AC Induction motor construction. Although for all I know it could only apply to the S/X.
Patent Images
Patent Images
It does indeed take quite a bit of energy to keep the Model S pack warm in cold temps. Especially to get it up to temp if it's been cold-soaked.
I wonder if on the Model 3:
1) The greater mass-to-surface area of the 2170 cells changes how subject they are to ambient air temp change.
2) They have insulated the pack at all. On the S, that large aluminum bottom plate was a giant thermal conductor... although there is an air gap inside the pack between the casing and the cells.
3) Chemistry has been tweaked at all for better performance at temperature extremes, hence less need for thermal conditioning in cold weather
OK, here we go. In the pictures thread somebody got a clear picture of the Monroney sticker:
Standard features -> Technical: 3 phase, six pole, internal permanent magnet motor
Standard features -> Technical: 3 phase, six pole, internal permanent magnet motor
OK, here we go. In the pictures thread somebody got a clear picture of the Monroney sticker:
Standard features -> Technical: 3 phase, six pole, internal permanent magnet motor
But what if I really don't want it to be true? Couldn't this just be another typo?
Six pole is interesting though, the Model S/X were four pole motors, if I remember correctly. Maybe this is linked to the higher switching frequencies in the inverter? Or maybe just the lack of rotor slip? The i3 also has a six pole motor, the Bolt even an 8 pole motor, but both have lower top speeds.
OK, here we go. In the pictures thread somebody got a clear picture of the Monroney sticker:
Standard features -> Technical: 3 phase, six pole, internal permanent magnet motor
Interesting. That does seem pretty definitive, however unexpected. Also note the city/highway break - 131 city, 120 highway, 126 combined. Most Teslas to date have higher freeway than city...
3Victoria
Active Member
Perhaps they are focusing more on city driving .... a taxi would tend to more city driving over highway driving.
Hopefully, the second motor in a AWD Model 3 will be optomised for highway ... giving the best of both worlds?
SageBrush
REJECT Fascism
Hah! I feel the same way. I presume that Tesla had to meet a fuel efficiency target in order to keep battery costs in check for the $35k base car price and PMAC succeeded.
I imagine that Tesla will continue to develop and use PMAC and AC induction concurrently for best fit to each car and as improvements and economics dictate. As battery costs come down the motor will become a larger fraction of the total cost and and then AC induction may once again be preferred.
Am I correct in saying that the high frequency of DU repairs is unrelated to the AC induction ?
SageBrush
REJECT Fascism
The cynical view would say they are influenced by the system which also uses city consumption rates in determining range. I'm just relieved that Tesla had the smarts to build out the Supercharger system.
omgwtfbyobbq
Active Member
I think so. I've read the DU repairs were from a combination of issues on high power RWD cars, and none of those issues were because Tesla used an AC induction motor.
Current state of drive unit noise issues? • r/teslamotors
This company makes products to ground the bearing shaft in variable frequency drive motors to prevent discharges through shaft bearings that cause bearing pitting and eventual bearing failure. I don't know if Tesla has added something like this to their AC drive units.
AEGIS® Shaft Grounding Rings for VFD-controlled Motors | Electro Static Technology, Inc.
JRP3
Hyperactive Member
It has been clear to me for quite some time, that Tesla will switch to PMAC as their main motor in the Model 3, maybe even all of their future vehicles, so this wasn't a surprise to me. My comment was more tailored towards those who kept arguing against the EPA document, because of a spelling error.
IMO the induction motor has it's place, maybe even more so in the future. And I could imagine them adding an induction motor to their AWD setup. The PMAC is just too efficient and too power dense not to use it, especially in a environment where range is king and the battery is the most expensive single part of the vehicle.
Actually induction motors are easier to handle in many aspects, than PMAC. So given Teslas reliability record, they better tried a lot harder.
You can make anything reliable and durable, but that means quality control and going the extra mile in testing. Tesla as I see it seems to live more in the future, than the present, which could be an issue.
But I think they also hired lot's of good established engineers from bigger OEMs to help them out when it not only comes to making a good product, but that product also staying a good product for a long time.
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