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Model S Plaid
- Thread starter BANKWUPT
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There is no proof that it's completely eliminated. Sandy Munro isn't an electric motor expert. He just said it looked impressive.
That is a hypothesis.
However, my take is that there is no ripple due to the difference in design between a standard reluctance motor and the Tesla unit. The Tesla has 54 discreet poles in the stator vs an SR with 8 or so. That gives it a much smaller angular change per step which is the major cause of torque ripple.
Tesla pulls this off by adding interpoles to the rotor such that it has 6 main and 12 sub poles biased with the permanent magnet groups.
Net result is all rotor poles align each electrical commutation (boosting torque) and each step is only 6.7 degrees which reduces ripple and also shifts what there is to a much higher frequency which is damped by the mechanical time constant.
https://cleantechnica.com/files/2018/05/ACTUAL-Rotor-close-up-with-laminates-3.jpg
JRP3
Hyperactive Member
Like engineering explained it can be a combination of both artificial lowering of torque + necessary loweing in the first few km/h. So I guess it's word against word at this point. And throw unaware users with little experience into the mix.
At quarter second API intervals the RWD 3 had a linear increase in power at full throttle all the way to the power limits. I take this to mean the torque isn't limited to address torque ripple on the PMSR motor after the first quarter second.
How long does anyone think the torque is held? CANBus logs on a RWD 3 launch would put this to rest.
Back on the topic of the roadster, I can't imagine any setup other than PMSW in front and dual induction in back for range, cost, power and weight.
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Linear increase in power with linear increase in speed does indicate fixed torque (current).
If Roadster were dual induction, how did Tesla get around the cooling issue?
I think it more likely thevrears are PMSR. PMSR also gives direct position feedback which is critical for controlling yaw.
JRP3
Hyperactive Member
Dual induction in the rear would be heavier and take up more space than the dual PMSRMs, plus the cooling issues.
JRP3
Hyperactive Member
SoylentBrown (on Twitter) had alluded to there being something new or novel about the Plaid drivetrain and that it had something in common with laundry machines. Previously there was speculation that meant it was direct drive (without a gearbox). I don’t have access to his tweets but saw this posted in the main investor round table thread.
I believe Elon’s tweet is also consistent with this idea. The Plaid motor would have to have a ton of torque to work direct drive...
Attachments
Artful Dodger
"Neko no me"
Yeah, its not that bad. There are numerous scientific papers published in the literature, available through a Google Scholar search. Here once such result:
Ma, Cong, et al. "Vibration and torque ripple reduction of switched reluctance motors through current profile optimization." 2016 IEEE Applied Power Electronics Conference and Exposition (APEC). IEEE, 2016.
From the Abstract:
"This paper proposes a differential evolution (DE) optimization-based current profiling method for simultaneous reduction of the torque ripple and vibration of switched reluctance motors (SRMs).
"The mechanism of torque generation in SRMs produces radial forces in addition to the required tangential force.
"It has been shown that the radial forces acting on the stator are the main vibration source in SRMs and keeping the sum of the radial forces constant can reduce the magnitude of the significant harmonics of the sum of radial forces and further reduce vibration by avoiding the resonance caused by those harmonics.
"A simple method is proposed to model the torque and radial forces generated in the SRMs while considering the saturation effects.
"The resulting torque and radial force models are then used in the DE optimization process to generate the current profile of each phase in the form of Fourier series, where the Fourier coefficients of each phase current profile are determined to minimize the torque ripple and significant harmonics in the sum of the radial forces."
"The mechanism of torque generation in SRMs produces radial forces in addition to the required tangential force.
"It has been shown that the radial forces acting on the stator are the main vibration source in SRMs and keeping the sum of the radial forces constant can reduce the magnitude of the significant harmonics of the sum of radial forces and further reduce vibration by avoiding the resonance caused by those harmonics.
"A simple method is proposed to model the torque and radial forces generated in the SRMs while considering the saturation effects.
"The resulting torque and radial force models are then used in the DE optimization process to generate the current profile of each phase in the form of Fourier series, where the Fourier coefficients of each phase current profile are determined to minimize the torque ripple and significant harmonics in the sum of the radial forces."
And here's the money shot: "Fig. 9. The waveforms of the measured torque and the actual optimal phase currents (conduction angle = 240°)"
The paper concludes:
"This paper has proposed a simple and effective optimal current profiling algorithm to minimize the vibration and torque ripple of an SRM.
The results have shown a significant reduction of the variation of the sum of the radial forces while retaining a low torque ripple by the proposed method compared to a nonoptimal current profile."
The results have shown a significant reduction of the variation of the sum of the radial forces while retaining a low torque ripple by the proposed method compared to a nonoptimal current profile."
So my conclusion is that smart algorithms and even smarter engineers have tamed torque ripple. PM me if you need access to the paper discussed above.
Cheers!
sickfox
Member
Saw a rolling clip of MS-P. I'm loving it. Hopefully it's not too pricey when it comes out.
Regarding that tweet, direct drive does not mean gearless. It is referring to not using intermediate hydraulics.
2023 Tesla Model S: The Future is Plaid For America's Favorite Electric Large Sedan | Carscoops
"However, recent newer models such as the Model 3, Model Y, Roadster 2.0, and Cybertruck have all stolen the limelight somewhat, with the large sedan now starting to fade into the shadows. Cold water has been poured on any significant updates, with no sign of a full redesign on the cards too.
So rather than doom and gloom, let’s take a positive approach and explore what a potential Model S replacement could look like with this illustrative design study."
"However, recent newer models such as the Model 3, Model Y, Roadster 2.0, and Cybertruck have all stolen the limelight somewhat, with the large sedan now starting to fade into the shadows. Cold water has been poured on any significant updates, with no sign of a full redesign on the cards too.
So rather than doom and gloom, let’s take a positive approach and explore what a potential Model S replacement could look like with this illustrative design study."
Yeah, its not that bad. There are numerous scientific papers published in the literature, available through a Google Scholar search. Here once such result:
Ma, Cong, et al. "Vibration and torque ripple reduction of switched reluctance motors through current profile optimization." 2016 IEEE Applied Power Electronics Conference and Exposition (APEC). IEEE, 2016.
From the Abstract:
"This paper proposes a differential evolution (DE) optimization-based current profiling method for simultaneous reduction of the torque ripple and vibration of switched reluctance motors (SRMs).
"The mechanism of torque generation in SRMs produces radial forces in addition to the required tangential force.
"It has been shown that the radial forces acting on the stator are the main vibration source in SRMs and keeping the sum of the radial forces constant can reduce the magnitude of the significant harmonics of the sum of radial forces and further reduce vibration by avoiding the resonance caused by those harmonics.
"A simple method is proposed to model the torque and radial forces generated in the SRMs while considering the saturation effects.
"The resulting torque and radial force models are then used in the DE optimization process to generate the current profile of each phase in the form of Fourier series, where the Fourier coefficients of each phase current profile are determined to minimize the torque ripple and significant harmonics in the sum of the radial forces."
And here's the money shot: "Fig. 9. The waveforms of the measured torque and the actual optimal phase currents (conduction angle = 240°)"
View attachment 499501
The paper concludes:
"This paper has proposed a simple and effective optimal current profiling algorithm to minimize the vibration and torque ripple of an SRM.
The results have shown a significant reduction of the variation of the sum of the radial forces while retaining a low torque ripple by the proposed method compared to a nonoptimal current profile."
So my conclusion is that smart algorithms and even smarter engineers have tamed torque ripple. PM me if you need access to the paper discussed above.
Cheers!
Nice, excellent writeup. So what could cause the delay? Is it just as several claim - that it's artificially there to distinguish it from LR or something?
JRP3
Hyperactive Member
That is my guess, plus limiting stress, and warranty issues, on rwd cars.
You have RWD Model S as well (which has induction), but no similar nerfing. I just find it peculiar.
JRP3
Hyperactive Member
RWD S also had issues with drivetrain components. Maybe Tesla wanted to play it safe with the higher volume 3.
For what it is worth... Under max accel off the line with my RWD Model 3 there is no hint of anything like "torque ripple". It is smooth as silk accelerating. I am imagining that torque ripple issues would have presented as something like vibration or stuttering power delivery, but there is no sign of any such thing. So, it doesn't "feel" like they are on the edge of trying to manage some undesirable phenomenon.
