user57037

That's a lot of traction! Have fun!

If you are going to 400 V why do you need 1000 phase amps? Is this motor running a big machine in a factory or something?

@Graham I am pretty sure the OP is measuring the phase current outputs from a battery powered ESC. So it is correct to say the current is coming from the motor controller.

Tamura L06P800S05 will get you to 800 Amps for 25 USD per channel. Tamura S29S1T0D24Z will get you to 1000 A but it is 5x the price. I know one guy who is basically re-creating a Tamura type hall-effect sensor using laser cut electric steel for the concentrator and off-the-shelf linear hall sensors PCB mounted in the gap of the concentrator. He does have to fight drift problems and temperature coefficients, etc. Whereas Tamura seems to already have that problem beat. But he is getting a 1000 Amp sensor for low unit cost (but not zero R and D cost).

I think divide and conquer. You let the current split up and flow equally through 6 busbars (so that is 200 amps per busbar). One of the 6 has an ACS 722 on it. The ACS772 is 100 uOhms and can measure up to 400 Amps. If necessary, you can add a restriction to the other busbars to mimic the 100 uOhms of the ACS722, but that might not be needed.

Copper is a terrible shunt material due to the high tempco. Around 4 percent for every 10 degrees. So we could call that 0.04/10 deg = 0.004/degree. That is 4 parts per thousand or 4000 ppm tempco.

One motor controller design I looked at used a 31 Amp current sensor even though it is an 80 Amp controller. They used copper trace to divide the current into two different paths and measured the current in one of the paths. Even though copper has a high tempco, in this case, both paths are mostly copper hand have the same tempco. So you could use copper busbar material with precise dimensions to divide the current into several pathways, and use a magnetic sensor to measure only one of them.

@SpehroPefhany 1000A * 0.05 V = 50 Watts. Maybe it is the heatsink that will bankrupt you.

Interesting question. Could it be workable to detect the heat from the arc and then use an SCR to blow a fuse or trip the BMS (whichever comes first)? NTC, resistor, comparator, SCR. That kind of thing.

Russel if I am interpreting right, it is your birthday. If so happy birthday. Your words fall on sympathetic ears (so to speak). I am trying not to be the difficult person who forces others to draw on their empathy reserve. But I know that sometimes I probably am that person. So I try harder to make up for it on good days when I have empathy to spare. Onward and upward.

It does seem like it would be a lot of work and not the kind that is fun.

Apology accepted without reservation. I NEVER doubted your intentions. I just (perhaps too stubbornly) felt I had to point out the effect your wording had on me. I do appreciate the difficulty of moderation. I may have even walked on the wrong side of the line drawing this all out, and for that I apologize, too.

Perhaps the user name could be redacted. I don't really care. Ie, I am not advocating that you should redact. But it would be a decision consistent with the rationale of deleting my question. Personally I think if the guy is that much of a problem it would be nice if people were aware of it.

Oh, I mean that in ee meta there is discussion of the user that is negative in nature. Very old posts like 10 years old or something.

By the way, searching on that user's name DID turn up some prior posts. Perhaps those should be deleted. I initially thought it must be a different person, but have now realized it is the same person.

I accept that you had to delete it.

That answer, which I admit could be classifed as a smart ass answer, would at least put you (not Null, per-se, but some moderator) on record.

It puts you on record. Any lack of trust on my part is more a matter of principle than any personal judgement. And again, I have not been mistreated through moderation on this site ever.

Noted.

Actually one example of a way to answer it would be to say "His account is constantly suspended because of violations which lead to suspensions. He is not being targeted unfairly."

"We are not hiding the plagiarism" "your previous question about the private details of a particular user's suspension is improper".

Its like you want to call some one a plagiarist, but somehow linking to the post would be an outrageous insult to their character. I don't get it. But it is obvious I am digging a dry well.

One post would suffice.

State the policy and delete the question. Its fine. You went beyond stating the policy and suggested that the question is improper.

What I have in mind is more a link in the suspension reason on the users profile. Not broadcasting on meta nor doing a bunch of research for me.

If you can't come up with a nice way to say something perhaps you shouldn't say it at all. It is your policy in the sense that you are bound by it, is what I meant. Not that you are the author of the policy. I will point out AGAIN that once the site says someone is guilty of plagiarism it is a little dubious to then stand on the ground of user privacy to avoid divulging any details about the plagiarism. If you wanted to protect privacy you could give no reason whatsoever. But as long as I stand accused of impropriety I will continue to reiterate my defense ad nauseum if necessary.

I guess my point is pretty simple. It is my opinion that faith in moderators could be increased by greater transparency where possible. I could be wrong and I have never had a problem with moderation applied to me here. So I am not griping on my own personal behalf.

If I am interested in something then it is my business as far as I am concerned. If you have a policy prohibiting you from telling me something that is your policy. But when you tell me it is none of my business and I shouldn't be interested or curious and that my inquiry is improper and reflects a defect in my character, well, that is insulting. Transparency is nice to have when possible. I agree with you about that. And I am aware that inquiries are often stymied by policies. That is the natural order of things.

I see you have doubled down. Interesting. I apologize for sounding judgy. My question was meant as a question not an allegation. I will try to do better in the future. Reading between the lines, I gather that there is much about the user in question that I didn't know but which is material. I am at peace with that. I still think transparency of moderator action is an ideal to aspire towards. But it is very clear that all moderator action is subject to review only by basically higher level moderators.

If you re-read what you wrote on that question you will likely see what I mean. If the question needs to be closed because policy prohibits you from answering then just say that. It is not possible to say "it is none of your business" or "it doesn't concern you" without being condescending and judgy. Then you closed the question so I couldn't even reply to your comment. Nobody can be perfect all the time. Moderation is a soul sucking endeavor because you have to constantly try to hold yourself to a very high standard. So I am grateful to those of you who do it. But you did ruffle my feathers.

not so much in this answer but in my previous question which was closed.

There is no way I can have a concern about how a moderator handled anything because I have so little visibility into it. I am not sure if you see it or feel the same way but the process seems to me to be so byzantine that it is actually designed to just prevent people from ever taking any action or getting a straight answer. I have no first hand reason to think the moderators are doing anything unfair. I will say that your condescending tone toward me ruffles my feathers a bit.

I am sure Jonk is right, but again it comes down to having a specification for how much variation you can tolerate.

When I worked for a kids toy company we had to test backlight brightness on the assembly line. I think we allowed a 10 percent tolerance or something like that. Can you tolerate 10 percent brightness variation or do you need 1 percent or??? I think a lot of times it is better to build and test something rather than be put off by a bunch of negative comments on the internet. I am sure if you want 0.1 percent control of brightness you will get into a whole host of difficulties. But if 1 percent is good enough maybe it won't be so hard. 10 percent should be easy.

You can use some type of precision op-amp circuit to achieve good control over current in different strings. It shouldn't be too difficult to get to 1% or less. Note that the LEDs themselves will have some variation in how they convert current into photons. I am not sure how large that variation is.

If and when you slap a ferrite on the cable, which you should definitely do, you want to look for a ferrite that has substantial impedance or attenuation at the frequencies where you are failing the worst. Some ferrites don't have much attenuation below 50 MHz. You need decent attenuation between 30 and 100 MHz. So look for that.

Also, the rating is a maximum allowable rating based on some type of rule or law or electric code. It is not correct to say that the cable will start conducting as soon as the limit is exceeded. It just means that you can't use the cable for greater voltages. Brand new cable tested in a lab will not conduct even with MUCH higher voltages applied for a short time.

I wonder if the title could be changed to something a bit more simple? Like: why does a cable have different voltage ratings for line-to-line vs line-to-neutral voltage? Seems like StainlessSteelRat may have answered based on the title rather than reading the whole question. Making the title match the question may help with that.

@MathKeepsMeBusy a coil of wire has reduced ampacity BUT the highest common temperature rating for magnet wire is something like 220 degrees (C).

Metric temperature units.

You can definitely run 80 Amps through a coil of 18 AWG magnet wire once for a few milliseconds. You can even do it once per day for many days. But whether you can do it every 4 seconds for 15 minutes is uncertain, and the details make a big difference. For example, 4 ms every 2 seconds is much worse than 2 ms every 4 seconds. Also, please take note that wire resistance increases noticeably when the wire gets hot. Every 10 degrees of temperature increase gives another 4% resistance increase.

The standard solution to this problem for many years has been to use a pendulum which does not expand and contract with temperature. Graphite fiber might work. Or Invar. I think this will be easier than measuring it.

To all of you all, there ARE materials with extremely low temperature coefficients of expansion. For example graphite fiber. So it could be possible to measure this. But I think it would be easier to measure the temperature.

Maybe try a labjack. One of the labjacks that has a 24 bit ADC. I don't think you would ever be able to actually get 32 bits of resolution in an ADC. Think about what that means. 5V / 2^32. Its 1.2 nV resolution.

It would be very convenient for those appliances which use induction motors. Three phase induction motors are a bit simpler than single-phase. Apart from that I am not sure if it is a big deal.

@BaardKopperud If we consider that L1 and L2 are different phases, then we do actually have two phases 180 degrees from each other. This is why I believe the monniker "two-phase" would be appropriate. It is like we have two phase "star." In a 208 V three phase star setup, L1 to neutral is 120 V and L1 to L2 is 208 V. But in 2-phase star L1 to neutral is 120 V and L1 to L2 is 240 V because L1 and L2 are phase shifted by 180 degrees.

Appliances that use 120 and 240 need 4 wires, L1, L2, Neutral and GND. The GND is not intended to carry any normal current, only fault current (short case to L1 or L2). So those appliances can take their 120 V from either L1 or L2 to neutral. If the center tap was not used as the neutral, the situation would be different and more like you say.

@RussellMcMahon in North America, the center-tap is designated as "neutral" and is bonded to the earth ground (in exactly one place). So L1 to neutral is 120 V. Also, L2 to neutral is 120 V. Pure 240 V loads do not use neutral (but they do use the earth ground as a safety ground).