JRP3
Hyperactive Member
Then why did Tesla us AC induction in the front of the Model 3 instead of the more efficient PMSRM?
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Model S Plaid
- Thread starter BANKWUPT
- Start date
-
- Tags
- Model S plaid Tesla Inc.
JRP3
Hyperactive Member
Yes and because of that, it has a significant delay on acceleration, like an ICE car. That's a huge no-no on a performance model.
JRP3
Hyperactive Member
Yes, I'm 99,99% sure that's the reason. If you watch the video, you might learn a thing or two about PMSRMs
JRP3
Hyperactive Member
Yeah, I'm 99.99% sure he's wrong. He even says they likely limit the power in software to lower the performance of the vehicle so it doesn't come too close to the higher spec models. Torque ripple doesn't necessarily negatively affect performance, only vehicle sound and vibration, and it's not limited only to hard acceleration. Here's a 5 year old article about dynamically controlling torque ripple, I'm quite sure Tesla solved the issue.
Charged EVs | A closer look at torque ripple – minimizing its effects on electric machines
Charged EVs | A closer look at torque ripple – minimizing its effects on electric machines
Yes, I'm 99,99% sure that's the reason. If you watch the video, you might learn a thing or two about PMSRMs
Avoiding torque ripple would involve reducing acceleration, not delaying it. Delay on a foot stomp is likely the anti-crash your garage wall safety feature along with preloading the drive train for longevity. Roadster 2020 is running the Model 3 type motors in the rear axle.
Also, the design of the Tesla motor has many more poles with smaller angle between electrical communications that a standard reluctance motor, so I doubt there is a torque ripple problem. Especially since any residual mechanical system induced ripple could be negated by varying the electrical drive signal.
I find this whole conversation very interesting.
I have a RWD model 3 and find the off the line acceleration quite acceptable, but not thrilling.
I am not in love with the way 3P was done having the AC motor in front so it has a FWD (pulling on the steering) bias during launch.
AC motor in back and PMSRM in front like they did on Raven seems like a better design. I suspect 3 was done "backwards" just because of the evolution of the 3 drivetrain as they brought their new PMSRM to market. They started with RWD for simplicity and then put the Performance AC motor up front just because they already had the line going putting PMSRMs in the back.
Personally, I would love it if they could do plaid with 3 PMSRMs... I would prefer not to have an AC motor in my Tesla (although Nikola could object) for efficiency, and reliability reasons.
The Tesla PMSRM is just really great engineering... a modern marvel.
I have a RWD model 3 and find the off the line acceleration quite acceptable, but not thrilling.
I am not in love with the way 3P was done having the AC motor in front so it has a FWD (pulling on the steering) bias during launch.
AC motor in back and PMSRM in front like they did on Raven seems like a better design. I suspect 3 was done "backwards" just because of the evolution of the 3 drivetrain as they brought their new PMSRM to market. They started with RWD for simplicity and then put the Performance AC motor up front just because they already had the line going putting PMSRMs in the back.
Personally, I would love it if they could do plaid with 3 PMSRMs... I would prefer not to have an AC motor in my Tesla (although Nikola could object) for efficiency, and reliability reasons.
The Tesla PMSRM is just really great engineering... a modern marvel.
Because my assumption is that the AC motor is giving more low end torque for those wicked launches.
Also, I think they design it so that the AC motor is there for hard launches, and the PMSRM is there for efficient highway cruising. So some gearing choices as well.
But mostly, I do think they have to make the PMSRM a bit "soft" at low RPMs in some way related to the different technology.
JRP3
Hyperactive Member
All the performance and high torque products are getting the PM motors, Plaid, Roadster, Cyber, Semi, I don't think assuming PM motors have less torque than induction is correct. Rotor magnetism has to be induced in induction, which is a loss, while it's inherent in PM rotors.
Artful Dodger
"Neko no me"
The LR RWD Model 3 has a single rear SRPM with no torque ripple issues. Why do you expect one to appear by adding a separate motor. (Hint: it won't).
Artful Dodger
"Neko no me"
Certainly not for reasons of efficiency. Replacing an AC motor with a SRPM motor at the front of Raven INCREASED the vehicles range, while adding an AC Induction motor to the front of Model 3 AWD has DECREASED the range.
The most likely reason Tesla chose an AC Induction motor for the front of Model 3 is that the SRPM motor is simply too powerful to be used in this lighter car:
- 3rd part dyno tests have MEASURED 380 hp at the wheel with LR RWD
- Semi uses 4 SRPMs to haul 80K lbs gross wt, or 20,000 lbs per motor
Similarly, time's ripe to do a chassis dyno test on the AWD 3. I'd like to know 3 things:
- how much power does the font AC induction motor make
- what is the power increase in the front motor with the $2K "Performance Boost"
- how does it compare to Raven's front SRPM motor power + weight
Last edited:
Certainly not for reasons of efficiency. Replacing an AC motor with a SRPM motor at the front of Raven INCREASED the vehicles range, while adding an AC Induction motor to the front of Model 3 AWD has DECREASED the range.
The most likely reason Tesla chose an AC Induction motor for the front of Model 3 is that the SRPM motor is simply too powerful to be used in this lighter car:
I'd like to see is a tear-down of the Model 3 AWD to compare size and weight of the front AC motor to SRPM. How about it @Ingineer ? You up for some more spelunking?
- 3rd part dyno tests have MEASURED 380 hp at the wheel with LR RWD
- Semi uses 4 SRPMs to haul 80K lbs gross wt, or 20,000 lbs per motor
Similarly, time's ripe to do a chassis dyno test on the AWD 3. I'd like to know 3 things:
Cheers!
- how much power does the font AC induction motor make
- what is the power increase in the front motor with the $2K "Performance Boost"
- how does it compare to Raven's front SRPM motor power + weight
The reason Tesla choose AC induction motor to pair with the SRPM motor is because it's trivial to free wheel the AC induction motor with very little efficiency loss because it only produces a magnetic field when it's energized. Using two SRPM will be less efficient because you can't completely de-energize one of them and let it spin without resistance. Tesla would need to introduce a clutch or other complex mechanical solution to reduce the drive-train drag.
JRP3
Hyperactive Member
I doubt that, they could have just built a smaller motor. The front induction motor is pretty small. More likely they chose it because it can be idled. Also since it doesn't use PM's it's probably cheaper to build.
It is
The 3 describing it
Lag in "off the line" acceleration
The others:
Anyone noticed a brief throttle lag?
General back and forth on 3 acceleration
Sluggish Off the Line Acceleration Model 3?
One theory is that it doesn't have torque ripple issues because they limit the torque at lower RPMs to avoid it...
Brando
Active Member
Torque ripple was designed out by that Greek fellow. May still be the most efficient motor design, am I right?
Remember the 4 magnets glued together? it was called _______ I for get.
It was the most efficient Sandy Munro had seen. But things do keep improving.
Slow startup might, just might be to lower impact on the drive train - drive shafts & reduction gears?
Seems quick enough, doesn't it ??
Remember the 4 magnets glued together? it was called _______ I for get.
It was the most efficient Sandy Munro had seen. But things do keep improving.
Slow startup might, just might be to lower impact on the drive train - drive shafts & reduction gears?
Seems quick enough, doesn't it ??
Last edited:
