Maximizing Copper Fill

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hias9   1 kW

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Maximizing Copper Fill

Post by hias9 » Dec 27 2020 7:25pm

Hub motor stators usually have a piece of wood and paper on top of each stator slot.
Is this additional insulation or too keep the copper windings where there are?

Would it be a good idea to remove these pieces and add maybe 1-2 strands of winding wire to increase copper fill?

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markz   100 GW

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Re: Maximizing Copper Fill

Post by markz » Dec 27 2020 9:28pm

Slot liner insulation protects the winding conductors during insertion into the stator slots.

The slot liner insulation also provides additional insulation between the motor winding wires and the stator laminations.

The slot liner insulation also provides extra insulation at the sharp edge where the motor windings exit from the motor stator slots.

Phase to phase insulation can also be used to add additional insulation where large voltage gradients are present between adjacent windings.

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Re: Maximizing Copper Fill

Post by larsb » Dec 29 2020 7:36am

you'll find that those extra wires don't give a large increase in fill if it's not a (really) crappy motor winding.

The other thing is that the windings closest to the magnets are more affected by eddy losses. I’ve seen some tests where it wasn't worth it to pack the final layer closest to the slot opening as the lower resistance was offset by the increased eddy losses.

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Re: Maximizing Copper Fill

Post by markz » Dec 29 2020 6:56pm

There was a discussion on :es: about if you could make a square wire if that would be beneficial.

Could be this one, search term "fill square" 10 pages worth
3 posts with "square" in same one
viewtopic.php?f=30&t=102934&p=1505953&h ... e#p1505953

Read the quote
viewtopic.php?f=31&t=65031&p=1197760&hi ... l#p1197760

Iron Fill
viewtopic.php?f=30&t=90037&p=1445084&hi ... l#p1445084

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ekline309   10 W

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Re: Maximizing Copper Fill

Post by ekline309 » Jan 05 2021 10:37pm

Square wire is great in theory but in my experience it is a huge pain, especially when you are moving from one layer to the next. This is the best article I've ever found about maximizing copper fill: https://ieeexplore.ieee.org/document/651289

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Re: Maximizing Copper Fill

Post by larsb » Jan 06 2021 12:30am

I’ve done some square wire winds, it’s really dependent on the way you shape the wire. This is a 60% winding.
F5428A80-C891-4365-9FAF-5BCA42ABB9B2.jpeg
F5428A80-C891-4365-9FAF-5BCA42ABB9B2.jpeg (83.96 KiB) Viewed 601 times
From there it’s hard to get a large increase in fill whatever method is used. 90% or whatever is mentioned in the paper won’t ever be wound on a motor coil.

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Chalo   100 GW

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Re: Maximizing Copper Fill

Post by Chalo » Jan 06 2021 12:42am

Makes me wonder where there's anything in using hexagonal wire. It would at least be able to pack in more densely, like square wire but easier to work with.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Re: Maximizing Copper Fill

Post by larsb » Jan 06 2021 2:52am

I don’t find rectangular wires to be that difficult but it’s true they cannot be wound as quickly as a softer/lower diameter multiwire wind. The thicker wires have the benefit of being bulletproof in comparison to the super thin wires on many chinese rc motors.

Anything less than a true 30% is a poor winding and anything above 60% is remarkable in my book.
Last edited by larsb on Jan 23 2022 8:18am, edited 1 time in total.

hias9   1 kW

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Re: Maximizing Copper Fill

Post by hias9 » Jan 21 2022 1:38pm

What are your experiences about the possible bending radius when using rectangular winding wire?
When rewinding a DD hub motor with 36 or 51 slots and 3 turns I would guess that using a single 5.5x3mm wire would not be possible, but one would have to use 3 5.5x1mm or even 6 5.5x0.5mm in parallel instead.

Does anybody have experience with this?

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Re: Maximizing Copper Fill

Post by Hummina Shadeeba » Jan 21 2022 6:26pm

i dont know where you got your square wire but i got a small amount from MWS. Its SUPER expensive. it was a huge pain to not have it twist and end up with worse than round wire if the wire used is anything smaller than 16awg and even that size was a pain.


most interesting to me is the square wire starts as round wire that already has the enamel and then they form it into the square shape. i asked about possibly crushing wires into the stator and without my adding any details MWS told me it was "child's play". squishing a wound tooth so as to get more wire in or further down in there away from the magnets sounds doable but a pain. More so the advantage seems in being able to crush the endturns of the stator after already wound so you have more room in the case and can use a longer stator.

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SafeDiscDancing   10 kW

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Re: Maximizing Copper Fill

Post by SafeDiscDancing » Jan 21 2022 6:55pm

Maximizing fill is always a good thing.

I just did a 104% rewind and it clearly shows itself in heat reduction.

Now I just need my "social reality" to permit my ability to enjoy it.

(right now I'm in a lockdown)

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Re: Maximizing Copper Fill

Post by Hummina Shadeeba » Jan 21 2022 7:05pm

SafeDiscDancing wrote:
Jan 21 2022 6:55pm
Maximizing fill is always a good thing.

I just did a 104% rewind and it clearly shows itself in heat reduction.

Now I just need my "social reality" to permit my ability to enjoy it.

(right now I'm in a lockdown)
how are you testing heat?

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SafeDiscDancing   10 kW

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Re: Maximizing Copper Fill

Post by SafeDiscDancing » Jan 21 2022 7:09pm

Hummina Shadeeba wrote:
Jan 21 2022 7:05pm
how are you testing heat?
When I went from an 11 turn wind to a 14 turn rewind it dropped the temperature drastically as is defined in the Grin simulation.

Basically I'm saying the Grin simulation is spot on and 100% valid if you put in good data.

Justin knows his shit.

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Re: Maximizing Copper Fill

Post by Hummina Shadeeba » Jan 21 2022 10:16pm

SafeDiscDancing wrote:
Jan 21 2022 7:09pm
Hummina Shadeeba wrote:
Jan 21 2022 7:05pm
how are you testing heat?
When I went from an 11 turn wind to a 14 turn rewind it dropped the temperature drastically as is defined in the Grin simulation.

Basically I'm saying the Grin simulation is spot on and 100% valid if you put in good data.

Justin knows his shit.
If ur dropping the kv I think that’s likely much more so going to be the cause of the temp drop and not the 5% copper.

Can u add 5% more copper in the simulator or u altered the resistance of the motor in a way that would be adding 5%?
Last edited by Hummina Shadeeba on Jan 21 2022 10:34pm, edited 1 time in total.

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SafeDiscDancing   10 kW

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Re: Maximizing Copper Fill

Post by SafeDiscDancing » Jan 21 2022 10:33pm

Hummina Shadeeba wrote:
Jan 21 2022 10:16pm
If ur dropping the kv I think that’s likely much more so going to be the cause of the temp drop and not the 5% copper.
Yes. The motor was designed to be operated at 36 volts and I am running 12S Li-ion which runs from 48 volts to 43 volts.

So the rewind simply adjusts the motor to a more realistic situation.

The lessoned learned is you need to know what you are doing.

But it was done because of an ERPM limitation of Sensorless mode so there is more upside if the controller was designed to handle it.

This setup only pushes the ERPM to 24,000 and I know there is room for that going way higher.

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Re: Maximizing Copper Fill

Post by calab » Jan 21 2022 11:29pm

The chinese sellers were right all along, motors ARE designed for voltages.
SafeDiscDancing wrote:
Jan 21 2022 10:33pm
Hummina Shadeeba wrote:
Jan 21 2022 10:16pm
If ur dropping the kv I think that’s likely much more so going to be the cause of the temp drop and not the 5% copper.
Yes. The motor was designed to be operated at 36 volts and I am running 12S Li-ion which runs from 48 volts to 43 volts.

So the rewind simply adjusts the motor to a more realistic situation.

The lessoned learned is you need to know what you are doing.

But it was done because of an ERPM limitation of Sensorless mode so there is more upside if the controller was designed to handle it.

This setup only pushes the ERPM to 24,000 and I know there is room for that going way higher.

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Re: Maximizing Copper Fill

Post by larsb » Jan 22 2022 8:58am

No, but i guess you´re trolling a bit there.

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Re: Maximizing Copper Fill

Post by larsb » Jan 22 2022 9:07am

Hummina Shadeeba wrote:
Jan 21 2022 6:26pm
i dont know where you got your square wire but i got a small amount from MWS. Its SUPER expensive. it was a huge pain to not have it twist and end up with worse than round wire if the wire used is anything smaller than 16awg and even that size was a pain.


most interesting to me is the square wire starts as round wire that already has the enamel and then they form it into the square shape. i asked about possibly crushing wires into the stator and without my adding any details MWS told me it was "child's play". squishing a wound tooth so as to get more wire in or further down in there away from the magnets sounds doable but a pain. More so the advantage seems in being able to crush the endturns of the stator after already wound so you have more room in the case and can use a longer stator.
got he wires from wires.co.uk. It' relatively expensive compared to round wire. I have to add that i never used square wire as it's known to be a bitch to wind. i've tried 5x2.5mm rectangular, 2x1mm etc, whatever maximises the fill factor on a given stator. For a 12slot 14pole motor the thickness should be <1mm to avoid getting too much skin effect if you plan to use the full rpm potential.

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Re: Maximizing Copper Fill

Post by hias9 » Jan 22 2022 9:55am

I plan to use it on a direct drive hub motor, so skin effect is not really an issue.
But because of bending radius I doubt that something like 5.5x3mm would make sense if the stator tooth width is only about 7mm. So instead I guess I would have to use 5.5x1mm 3 in parallel or 5.5x0.5mm 6 in parallel.

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Re: Maximizing Copper Fill

Post by larsb » Jan 23 2022 5:02am

The radius will be the width of the tooth minus some mm, the wire bundle can be flattened a bit. I had to do it on some winds, not really because the wires were thicker and hard to bend but because the copper fill grew so much and the motor wasn’t spaced for the copper.

A 12s14n motor like the 80100 maxed at about 7000 rpm has a frequency of roughly 800Hz, i estimated ~1kHz when looking at skin effect. What would your hub motor have at your max speed?

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Re: Maximizing Copper Fill

Post by hias9 » Jan 23 2022 8:36am

130kph would be 1100rpm and with 16 pole pairs it would be less than 300Hz. So I doubt that skin effect is a big issue here.
Bending radius would be less than 4mm in this case. So I doubt that this would be possible with 5.5*3mm wire without damage.
So you think 5.5*1 3 in parallel would be fine or do I even need something like 5.5*0.5 6 in parallel?

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Re: Maximizing Copper Fill

Post by Hummina Shadeeba » Jan 23 2022 10:45am

“heavy build” stuff that’s double coated shows better flexibility on a tight radius

Page 9 shows thicker insulation doing better. they sell thicker insulation rectangular wire
https://www.hca.hitachi-cable.com/produ ... ire_en.pdf
You’d be doing a slightly tighter bend than in their test but then again even if the enamel were to crack that crack would be touching wire that wasn’t cracked and you could rely on that other non-cracked wire’s insulation.


Or maybe could add the smallest spot of kapton tape at the bend.

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Re: Maximizing Copper Fill

Post by hias9 » Jan 23 2022 12:14pm

Do you mean page 8 (the page which has two pictures on it) ?
The two wires which are compared there have the same insulation thickness (only slightly different at the edges).

I also found this pdf some weeks ago, but did not find any place where to buy that high reliability Hitachi wire in smaller quantities.

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Re: Maximizing Copper Fill

Post by Hummina Shadeeba » Jan 23 2022 1:32pm

Yea page 8. It says .03 compared to .04mm insulation thickness.

If anyone knows a place to get reasonably priced rectangular wire please post it. MWS wire is crazy expensive and only place I’ve found.

Or knowing it’s insulated prior to shaping maybe there an easy way to make our own.

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Re: Maximizing Copper Fill

Post by hias9 » Jan 23 2022 5:32pm

It's not a comparison of .03mm vs .04mm
The layer thicknesses are the same in both cases (only the value in parenthesis which is the minimum layer thickness at the corner is slightly different).
It's a comparison of the Hitachi wire against common wire of this size.

I highly doubt that it's insulated before shaping.

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