Impact of Field Weakening (FW)
- Thread starter Tomorrowwedietodayweride
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It makes total sense. When people compare apples with oranges, then that makes no sense.
So, the (clearly smart) Indian or whatever guy in that video there, he showed that in an apples with apples comparison (ie the only genuine comparison), field weakening is a "waste" as regards all in the image in yellow, and one would better only use FW if one feels one must achieve a higher speed than what is most efficient for the equipment components in use.
Again, he showed. It's reality.
While Grin Tech graphs are theoretical approximations based on model assumptions, you can listen to him explaining it even.
(as if it wasn't obvious, but it is: Graphing apps always are)
The Indian(??) is absolutely worth watching/reading too. I have found a lot lot lot since Nov (full time) and almost nothing is as sensible, educated, and smart as what I read from that guy. That's IMHO of course, others' will differ.
PS: why "almost nothing"? Because these articles are the same league, IMHO: ElectricBike.com
(Ron is certainly here too, I've chatted with him, if Eric, I don't know, I am too new here)
My Fardriver only enters field weakening if it is needed to reach the demanded phase current.
My scooter with the ND72680 took 7kw from the battery to drive at 100kph with activated field weakening or without, there is was no real difference.
The difference in power came when I wanted to accelerate from 100 to the maximum speed.
Without field weakening power was 12kw @100kph with full throttle and acceleration was slow. With field weakening power was 23kw and acceleration was much faster.
Shure more heat was generated and efficiency was lower, but you get faster acceleration.
I also had a motor with a 20% lower kv. To reach the same speed I had to use more weakening field and had lower effiviency, but this motor accelerated much faster from a standstill. During my normal daiöy driving there was no noticable difference in power consumption between these two motors. Only during long Highway use you could see that the field weakening decreases the range by 10-15%.
My scooter with the ND72680 took 7kw from the battery to drive at 100kph with activated field weakening or without, there is was no real difference.
The difference in power came when I wanted to accelerate from 100 to the maximum speed.
Without field weakening power was 12kw @100kph with full throttle and acceleration was slow. With field weakening power was 23kw and acceleration was much faster.
Shure more heat was generated and efficiency was lower, but you get faster acceleration.
I also had a motor with a 20% lower kv. To reach the same speed I had to use more weakening field and had lower effiviency, but this motor accelerated much faster from a standstill. During my normal daiöy driving there was no noticable difference in power consumption between these two motors. Only during long Highway use you could see that the field weakening decreases the range by 10-15%.
scianiac
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Honestly this is all of questionable value considering the effect of field weakening/MTPA depends so heavily on the motor design, yeah it's hideously inefficient in a motor with almost no salience because that motor was never designed to use it but on a motor with tons of salience it's a much different story. Some proper motor controllers will not only have MTPA but also MEPA (maximum efficiency per amp) which uses the salience of the motor to improve the efficiency in some regimes.
Since we're mostly talking about hub motors that generally have pretty low salience the results are never going to be amazing but some may be OK depending heavily on the motor design. The best recommendation is to try it with your motor and test it yourself, don't just turn it on and don't bother checking to see how much power is wasted and of course to not plan a hub motor build around using it.
Since we're mostly talking about hub motors that generally have pretty low salience the results are never going to be amazing but some may be OK depending heavily on the motor design. The best recommendation is to try it with your motor and test it yourself, don't just turn it on and don't bother checking to see how much power is wasted and of course to not plan a hub motor build around using it.
Yes, makes sense. Many windings.
Interesting! And: Phew, you have a powerful bike!! And: from 100 to max speed? What is max speed???
Mine won't even go 100 (and I am glad, it's a Chinese frame)While Grin Tech graphs are theoretical approximations based on model assumptions, you can listen to him explaining it even.
(as if it wasn't obvious, but it is: Graphing apps always are)
How do you know this was theoretical? in the thread there is no mention of that image being theoretical, and that test is surrounded by non-theoretical tests, so can you please point to what part of that thread indicates said test is theoretical? otherwise you're just making stuff up.
Said test is extremely easy to reproduce and there's no reason their particular test would need to be 'theoretical'.
What thread? I don't understand, or you misunderstood me, I wrote "Graphing apps always are". It's scientific/mathematical fact.
Or do you mean "the Indian guy"? He's actually (likely) Filipino, I figured out from his videos.
Yes, he too is electrotechnical engineer but only shows what he is testing. I like it.
"That's IMHO of course, others' will differ".
Yes, he too is electrotechnical engineer but only shows what he is testing. I like it.
"That's IMHO of course, others' will differ".
Oh, you didn't even read the link i posted before calling it theoretical.
So you're just making stuff up.
As for graphing apps, well, i write them for a living for a university math department head with insanely high accuracy standards, so i think i am qualified to question this claim too.
Even if you used integer rounding to do graphing math ( unlkely for any software to be written this poorly ), it would still be accurate enough to show the above effect and efficiency loss curve.
Yeah i'm wrong about assuming the race of the video poster, but you provided us no video link for context.
So you're just making stuff up.
As for graphing apps, well, i write them for a living for a university math department head with insanely high accuracy standards, so i think i am qualified to question this claim too.
Even if you used integer rounding to do graphing math ( unlkely for any software to be written this poorly ), it would still be accurate enough to show the above effect and efficiency loss curve.
Yeah i'm wrong about assuming the race of the video poster, but you provided us no video link for context.
scianiac
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Really the more interesting graphs are the two below that one in the thread that show it results under a load and while the efficiency does drop in FW it's not very much. I'm kinda surprised it's this good for a hub motor, although the total increase in RPM is isn't huge either.
If I recall I get something like 200% if base RPM with FW on my LR small block (which is a IPM motor with lots of salience) and that's loaded (including some hideous rolling resistance from super low pressure Tannus insert DH tires), bike was geared for around 18mph and was doing 42. That was just a test though and I never actually ride above 18 and that was with MPTA so the full 130A of FW (100% of phase current limit).
There are some other interesting variables here, like the actual RPM of the motor determining your iron losses, so some of the additional losses are just iron losses from increasing the RPM which you would get regardless if you used FW or increased the voltage. Maybe that would be slight IDK for that motor and RPM but still interesting to point out.
If I recall I get something like 200% if base RPM with FW on my LR small block (which is a IPM motor with lots of salience) and that's loaded (including some hideous rolling resistance from super low pressure Tannus insert DH tires), bike was geared for around 18mph and was doing 42. That was just a test though and I never actually ride above 18 and that was with MPTA so the full 130A of FW (100% of phase current limit).
There are some other interesting variables here, like the actual RPM of the motor determining your iron losses, so some of the additional losses are just iron losses from increasing the RPM which you would get regardless if you used FW or increased the voltage. Maybe that would be slight IDK for that motor and RPM but still interesting to point out.
??? Why so rude?
If you see any link in your post before mine, you could hint at the link again out of courtesy?
I certainly would not intentionally ignore a link you or anyone else sends me, makes no sense to suggest such thing.
"but you provided us no video link for context."
Yet another wrong, in a single post, please look closely where the link is:
or simply refrain from criticizing everything I write? Why would you?
Yet another wrong, in a single post, please look closely where the link is:
or simply refrain from criticizing everything I write? Why would you?
I am not affiliated with anything or anyone I am academic researcher.
I am academic researcher.
Just to try to make things easier for everyone:
@Tomorrowwedietodayweride
Perhaps it would have been easier for readers to find and follow, if you placed your links within the text of the post where they would show up as linked items, rather than in an image?
I am not certain about which of Neptronix's posts of his being referenced is the right one, but this one
endless-sphere.com
does have a link to a page in a thread about that particular controller, where it appears the graph in that post came from. Hopefully that's useful.
@Tomorrowwedietodayweride
Perhaps it would have been easier for readers to find and follow, if you placed your links within the text of the post where they would show up as linked items, rather than in an image?
I am not certain about which of Neptronix's posts of his being referenced is the right one, but this one
Impact of Field Weakening (FW)
endless-sphere.com
I hope you understand why i was rude. I am a nice person but intellectual dishonesty pisses me off > 9999999x more than the average person.
But you intentionally called it a simulation without reading it and also threw out the entire field of statistics while you were at it.
That's why i was offended and why i chose to be rude in response.
As for your source I wasn't sure this youtube channel was your source of information; that black text in the image contains english so broken it looks like the results of LLM output or auto-translate. I'm not sure if this is a screenshot of someone's presentation that has more detail you didn't provide.
You don't talk like, or conduct yourself like an academic researcher if you are one.
An academic researcher would have experience with graphing applications and use them daily and never claim 'all of them are inaccurate' because there is at least ONE they use and respect the accuracy of.
An academic researcher would also have lots of experience being wrong about things due to the fact that establishing good methodology is an iterative process, so they'd actually LIKE to hear a counterargument and be corrected.
I don't care if you got your PhD at Stanford or 'The School Of Hard Knocks'... if you are going to make a big contradictory claim, you need to bring big evidence and don't be surprised when people staunchly question those claims if you don't.
I certainly would not intentionally ignore a link you or anyone else sends me, makes no sense to suggest such thing.
But you intentionally called it a simulation without reading it and also threw out the entire field of statistics while you were at it.
That's why i was offended and why i chose to be rude in response.
As for your source I wasn't sure this youtube channel was your source of information; that black text in the image contains english so broken it looks like the results of LLM output or auto-translate. I'm not sure if this is a screenshot of someone's presentation that has more detail you didn't provide.
You don't talk like, or conduct yourself like an academic researcher if you are one.
An academic researcher would have experience with graphing applications and use them daily and never claim 'all of them are inaccurate' because there is at least ONE they use and respect the accuracy of.
An academic researcher would also have lots of experience being wrong about things due to the fact that establishing good methodology is an iterative process, so they'd actually LIKE to hear a counterargument and be corrected.
I don't care if you got your PhD at Stanford or 'The School Of Hard Knocks'... if you are going to make a big contradictory claim, you need to bring big evidence and don't be surprised when people staunchly question those claims if you don't.
