Nano-scale wire insulation useful? 2

[Flamefront]

Guys

In considering transformer/solenoid/electromagnet coil packing density, would it not be useful to have the thinnest possible insulation on the wire as possible (to confirm the obvious)? At some point, the max voltage that can be carried will be limited by the thinness of the insulation...before arcing would occur.

I'm working with a start up company that can lay down thin films of insulative elements and I want to flesh-out this application.

If they lay down a uniform insulative layer on top of a wire that is 0.1 micron thick, is that thinner than industry standards now? How much of an improvement is this over current practice?

Finally, is there one element that is preferred for an insulative layer (ceria, etc.)?

Thanks for any input you can offer...

 

[IRstuff]

Thinness is only one aspect. Durability under usage and handling are also important. Moreover, once the insulation is thinner than about 25% of the diameter of the wire, there's no practical necessity for any thinner insulation.

If you look at conventional magnet wire, it's insulation is already at the level, therefore, for most applications, there is no additional benefit to be had for what would presumably be a more expensive process.

TTFN

 

[MacGyverS2000]

From another standpoint...

How much is the thickness of the average industry-standard wire affecting packing density right now? If you could increase packing density by only a few percent (at best?), is it really worth the price increase?


Dan - Owner

http://www.Hi-TecDesigns.com

 

[Flamefront]

Good points, guys, but in some long ago discussions with BOSE,they were going to the trouble of making square wire to increase the packing density on voice coils.

In automotive applications, it is the packaging that is always the problem, even a 10% reduction in size is important.

IRStuff: Can you expand on why having insulation less than 25% of the wire diameter is not desirable or beneficial (outside of packaging)?

Thanks for the discussion...

 

[VEBill]

For high current (non-superconducting) applications the wire needs to be much much thicker than the insulation. This seems to indicate that the best application of untrathin insulation would be on very very fine wires where the thinness of the insulation would actually make a significant difference. In other words, not so much speakers, solenoids, and other high current applications. Maybe more for ultra-dense inductors and low power signal transformers.

But seeing that the designers of High-Q coils for RF take pains to separate adjacent turns, my gut tells me that tightly packing the turns would result in a low-Q coil. Thus, unless the coil is wound differently, ultra thin insulation might not be very useful for RF.

Sounds like a solution is search of a problem.

How about high density batteries? Dell laptop batteries were in the news recently and they mentioned that the foil layers were separated by 25 microns. Any stray particals and the battery self-destructs.

 

[MJR2]

Would the insulation be thermally more conductive than that now available. As we get smaller in wire diameter the space taken by the insulation becomes significant thermally. For me thinner is better. And the space factor improves as well. All good things for a price.

Mike

 

[sreid]

One important feature of magnet wire insulation is it's toughness. Magnet wire insulation takes a real beating during high speed coil winding. I doubt that micron thick coatings would hold up to this abuse.

 

[IRstuff]

That was just a swag. At some point, the insulation is no longer the issue. There are obviously exceptions. Bose and other speaker manufacturers want certain performance and price is flexible. Other applications are not so flexible on price.

TTFN

 

[VEBill]

I think you accidently reversed the words 'price' and 'performance' regarding Bose.

;-)

 

[IRstuff]

I said they "want" not that they "had" ;-)

TTFN

 

[MacGyverS2000]

Flame,

The square wire issue is another dog altogether.

If we assume circular cross section coils stacked directly on top of one another, you are only using 78.5% of your available space for power transfer... a square conductor can use 100%. If the round conductors are interleaved (edge new layer fits into the valleys created by the previous), the value jumps up to around 93% usable space. Still, 7% improvement is nothing to scoff at.

So, you have to ask yourself what kind of improvement in usable space are you going to get by using thinner insulation (a higher percentage return when used on thin wires, almost nothing on larger wires), the compare it to the "abuse" factors mentioned above.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[bogeyman]

I can,t see any point in reducing insulation thicknes to such small dimensions. Existing enamel insulated wires are already at the micron thickness on small size wires.

There have been several attempts to use very thin insulations on aircraft wirng systems to reduce weight etc one popular wire type which found great favour was kapton insulated, the insulation thickness is about 1.5 thou and is very good at its job, that is untill it gets damaged by overload or abrasion. The charred remains at the damaged point of the insulation carbonises and becomes a reasonable heating element that does not draw a significant current to trip the circuit breakers but does draw enough to get the remaining insulation hot enough to charr a bit more insulation and so on...
There are a large number of disapeared airliners for which some authorities believe the blame lies in kapton wire, kapton wire is no longer installed on aircraft.

I dont think that a nano insulation will ever be seen as safe by anyone whose been involved with kapton wiring.

If you use square wire to wind a soleniod you will reduce the DC resistance to pi/4 times the round wire equivalent.
This may be good for a loud speaker motor and may benefit other power tranducers as well. It costs more to make square section wire but it can be done at low cost in volume, the problem comes with winding it from drum to coil since you have to keep the wire from twisting.

Square wire was once used to make conections between the screw terminals of the components in radio sets (in the 1920's) the theory being that a greater area of wire was gripped by the terminal. In measurements I have made of this technique it does not seem to be worth the trouble since I could not achive anything better than a few micro ohms of change.

 

[BobbyNewmark]

You might look into the superconductor industry. They deal with low voltages, unusual coils, and assemblies that have to survive being fired in a kiln.

 

[BrianR]

Wire used in aviation needs to be as light as possible so if you can produce a worthwhile weight reduction then there is likely to be interest. Durability is an issue here though.

 

[sigmanut]

I'm new to this but it seems like there is really not very much conversation here about the voltages generated in a coil when the circuit is opened. If this is a relay or solonoid application, very much care would have to be dedicated (taking up more room) to prevent the coil from shorting the first time it was deenergized. That voltage generated is not related to the 12 volts design of the coil but however much is generated by the magnetic field colapsing. Thin insulations breakdown with this event.

 

[bogeyman]

In response to Sigmanuts point,
If you are intending to drive an inductive load from semiconductor switches it it normal to add a commutation diode across the coil, this will prevent a destructive high voltge spike from ever occuring however this is at the expense of a delay in the decay of magnetic field. A zener or varistor shunt (with a break down voltage lower than the maximum voltage that any other connected component can withstand) over the switch will provide protection for the switch with only a little increase in the fall time. The sort of time periods involved will typicaly be in the region of 1 to 500 milliseconds dependening on the magnetic circuits characteristics and the inductance and resistance of the coil.
A huge quantity of varistors were installed in older electro-mechanical telephone exchanges to prolong the life of relay contacts without delaying the operating speed (they used to have to run at faster than 10Hz to cope with pulse dialing methods)we used to call them red smarties (trans M&Ms).

 

[sigmanut]

Exactly what I was getting to bogeyman. Thus if those space eating components are not used, this nano-thin insulation will breakdown immediately. This is a large part of your problem flamefront.

 

[psuedoAE]

Care must also be given to the insulations ability to withstand the voltage potential during operation. Unless this material is some kind of new, higher withstand material, it's likely it will only be useful in very low-voltage applications. I am not sure what the insulation resistance is, but general a 1-mil insulation is only good to a practical 200V in electronic wire. Not sure what magnet wire thickness is required to withstand per mil, but a micron is incredibly thin, and may not be able to operate in most day-to-day industrial applications that I think most on this forum are more familiar with.

 

[jimkirk]

Maybe there's an application here for constructing Litz wire. Hundreds of very small gauge strands, braided in parallel to reduce the effects of skin depth. Strand to strand voltage would be near zero. Overall insulating sleeve would be added. With the individual strands of wires down to the order of 0.01 mm in diameter in some cases, there may be some benefits to thinner insulation for increasing the conductor cross section efficiency.