Has anybody wound their motor with square silver wire?

S

swbluto

10 TW
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May 30, 2008
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Just curious if someone has done this, since I think it would result in the lowest possible motor resistance (And, thus, highest motor heating performance limit.).

I'm also curious, what kind of improvement would this give over a normal motor wrapped with round copper wire?

I think triangular wire might also work.
 
Is any company out there now even using square copper wire in their motor offerings? I had no idea there even was such a thing but google comes up with this-

web%20wire%20anime.gif


http://tanac.eu/sx.aspx
 
I plan to.
http://www.mwswire.com/microsq.htm
prolly with copper though. Heavy gage stuff
I was a bit suprized to see aluminum as "magnet wire"
 
With silver only being at best ~10% more conductive than coppper, today costing almost $300/lb more than copper and many motors using 1/3 lb or $100 worth of silver, whether the best use of the money would be somewhere else in the system?

Or is silver lighter, or less resistive as it gets hotter? I know copper gets more resistive as it gets hotter.

Or are some of these numbers wrong?

best
d
 
There's not a big difference in conductance between Copper and Silver and you'd probably have to do your own insulation...

Square wire is a bit more vulnerable to insulation breakdown on the corners. If you can wind it without it twisting, you'll get a slightly more dense fill, I suppose - better heat transfer, too.
 
I think Astro winds thier motors with octagonal platinum, have you tried that? :wink:
 
u sure it's not hex?
i think that would be the best of both worlds. (round+square)

don't really see the need on a vehicle where u have the space to fit a slightly larger motor that will get u the same gains if not more for less outlay.
the way things usually go, shortly after you spend all that money fullerene wire may trump all, if allowed.


http://www.diyguitarist.com/GuitarAmps/SilverMyth.htm
http://www.diyelectriccar.com/forums/showthread.php/silver-wire-better-choice-wind-coilsi-23806.html
http://www.amsc.com/products/htswire/index.html
 
I'm going to post something that could potentially demonstrate my complete ignorance, but.....

What about low wind count, with parallel strands of small wire?

You know...the theory of current flowing along the surface of the wire.
 
TPA said:
I'm going to post something that could potentially demonstrate my complete ignorance, but.....

What about low wind count, with parallel strands of small wire?

You know...the theory of current flowing along the surface of the wire.
Click to expand...

You're referring to the skin affect which becomes more pronounced as frequency increases and becomes critical at radio frequencies, but when it comes to motors, you're more or less talking about electrical RPM type of frequencies and that corresponds to less than a kHz or two in most motors. I don't honestly think the difference would be significant between "big wires" and "small wires". Talking about big wires and small wires though - it seems fairly intuitive that one could get a better "practical" packing ratio with small wires when you're working with such limited space so small windings would probably help.
 
swbluto said:
....it seems fairly intuitive that one could get a better "practical" packing ratio with small wires when you're working with such limited space so small windings would probably help.
Click to expand...
Yes it does, but actually there's little difference, either way, between single strand or multistrand, with regard to fill factor. The choice has more to do with the ease of winding.
 
You will find in my bike build thread that I originally planned to re-wind my motors with square silver wire.

I tried winding square wire on a motor, and it's lead me to completely abandon the idea that I would be able to get better fill. The wire twists and doesn't lay right, and by the time you finally mash it down with your winding flattening tool, you've all ready damaged the insulation. I can do round wire justice, and get a pretty darn good fill. I struggled for hours with square wire, and ended with nothing.

Silver does have an advantage, and it should be worth at least 1-2% in motor efficiency. That can mean an extra 10-20% power handling ability in a motor that was 90% efficient.
 
TPA said:
What about low wind count, with parallel strands of small wire?
Click to expand...


it's called Litz wire.
according to this online book it actually has "poor filling factor".
however a possible reason for using Litz in a lo freq motor might be "significant reduction of eddy loss".

the CSIRO solar challenge hub motor (which happens to be axial flux) used Litz wire in its design.
iirc their controller was high freq, so there was the traditional benefit of reducing skin effect as well.
 
I think TPA is just referring to multi-stranding

I don't think there's much in the way of eddy currents in the wire, when you have an Iron core. I guess that's why Litz wire is usually only used for Ironless motors.
 
liveforphysics said:
You will find in my bike build thread that I originally planned to re-wind my motors with square silver wire. .....

Silver does have an advantage, and it should be worth at least 1-2% in motor efficiency. That can mean an extra 10-20% power handling ability in a motor that was 90% efficient.
Click to expand...


help me understand that.

Where 1-2% increase in efficiency translates to 10-20% power handling at 90%. I am not being SA or cute, would like to understand that.

Thanks

D
 
D,

The difference in the losses between 90% efficiency and 91% efficiency is 10%.

So, if the efficiency increases from 90% to 95%, you are almost doubling the continuous torque rating.... assuming that the efficiency figure is achieved at that torque level, of course........
 
Well stated Miles.

If an 80% motor can handle 1000w, the same motor wound to be 90% efficient can handle 2000w, and the same motor wound to be 95% efficient can handle 4000w, and if wound to be 97.5% efficient, despite the tiny 2.5% improvement in efficiency, that same motor can now handle 8000w.

A tiny gain of 2.5% from a 95% efficient motor results in a motor with twice the power handling ability.


This is why spending $100-200 in silver wire, and many hours of time and effort in winding don't seem all that crazy. For situations with bikes fitted with 2 motors, identical performance could be realized in a lighter weight and much more simple and compact drive system by the fitment of a single motor which has been re-worked to yield half the in-efficiency of the pre-modified motor.
 
Yes, the last bit of efficiency makes the most difference :D

One qualification to this. Normally the efficiency figure quoted for a motor is the maximum achievable - this is at the best amps input for a given voltage. The max. continuous torque rating would normally be at a higher amp input than this and so would not attain maximum efficiency.
 
This must have been suggested before, but I don't see any mention of it here: what about using thin copper foil wound in a single spiral coil. The edge of the foil is obviously a vulnerable point for the insulation, but an additional coat of insulation could be applied after winding. Is copper available in thin enough foil? Do eddy currents become a problem then?
 
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