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Insulation of enameled copper wire
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TOPIC: Insulation of enameled copper wire

Re: Insulation of enameled copper wire 2 years, 3 months ago #769

tech1 and spectre
thank you I think that I will try to use drawn wire hard and I will see the test results.
Now I have another question..Did you know something about round copper enameled wire which can be flattened? A standard product PEI+PAI round witch will be flattened and use after.???

Re: Insulation of enameled copper wire 2 years, 3 months ago #770

Coated copper can be flattened. Although, flatened bare copper can be coated as well. Two different processes that give different results.
Coating copper then flattening can only be flattened so much,typically 5:1 maximum ratio (thickness to width ratio )before coating begins to loose adhesion to conductor and begins to crack off. Also, this process mostly pulls out all of the elongation out of the wire returning it back into the hard condition. This process also gives you a different resistivity ( ie: 3% higher than typical soft wire ). Which can cause trouble if not taken into account if the wire is heated high enough to shift the resistance.
On the other hand, coating the pre flattened copper is more difficult but higher aspect ratio's can be used along with none of the physical properties and resistivities being affected due to the curing temperatures of the polymers. The only draw back typically is edge coverage. Although, this can be overcome with proper processing.

Re: Insulation of enameled copper wire 2 years, 3 months ago #771


ok.... but regarding the flatening of the round copper enamelled wire. After flatening the adherence is very low. There is a special method for cleaning of the bare wire -round (for example using of water with alcohol) before enamelling process, and afther this cleaning, enamelling and in the end flatening the adherence is good? Please tell me if you know other cleaning methodes of bare wire before enamelling, others than the normal cleaning with water and scotch brite.
Thank you

Re: Insulation of enameled copper wire 2 years, 3 months ago #772

Cleaning of the wire is not what is breaking down the adhesion during the flattening process. during the flattening process the wire is elongated as well as compressed beyond the strength of the adhesion strength of the polymer to the wire. PEI with an overcoat of PAI is a good choice for this although there are other polymers that work as well and possibly better for this process. As for cleaning of the wire for better adhesion I have always seen better results with adhesion using a polymer with compounds in it that promote adhesion to certain alloys. Also, cure of the polymers are critical as well. whats worse than a little bit of drawing solution on the wire before coating is micron sized fines pressed into the alloy during the drawing process. If your draw solution is heavily loaded with fines, this can cause major adhesion problems.

Re: Insulation of enameled copper wire 2 years, 3 months ago #773


Tried to respond last night but timed out so tonight I will do word document first. Glad to see response from Tech1.

Adhesion is always a funny thing and Tech1 does a great job explaining what I was going to say. Coating wire is like painting any surface. If the surface is clean, not too smooth or slick, and the coating properly coats and bonds to the surface you have good adhesion.

When you use wipes, etc on the wire you have to be careful to frequently move the wire to a clean spot because what you wipe off the wire gets on the wipe. After a while you are then applying it back onto the wire. When you use an abrasive like Scotch brite you are literally ‘sanding” the wire. That produces additional copper dust which gets applied back on the wire.

While I don’t know what make equipment you have, the pre-annealer burns off some of the dirt, grease, and lubricants on the wire. Some annealers have steam injected into the annealer tube, some have a water bath that is used to quench and cool the wire. This produces steam which seals the tube and keeps oxygen from discoloring or oxidizing the wire. (Oxidized wire will almost always have adhesion problems). Some annealers also have nitrogen injected into the tube to prevent oxidation.

Coating shaped wire is challenging but only because you have flats and corners to coat equally. GE used to run some shaped wire through a Turks’ head device to change the dimensions slightly. It allowed them to get a variety of sizes from a single size. Since the wire was used in oil filled transformers minor problems with the insulation were minimized.

Again it depends upon your equipment and operation speeds, etc, but it would be a lot easier to take round wire, flatten it with something like a Turks head and then coat it with enamel. Since the same piece of equipment could be used to flatten the bare wire or the enameled wire, it would make more sense to do it while bare. Coating flattened round wire is much easier than coating shaped wire.

Perhaps Tech1 can give some insight as I know he makes a lot of specialty wire with a variety of alloys. It still seems to me that flattening it before coating makes the most sense.

Re: Insulation of enameled copper wire 2 years, 3 months ago #774

Dear tech 1, Richard

I have to produce round wire which will be flattened. This is a must. I am using enameling equipments with drawing machine, bare wire preparation (washing device with water and scotch-brite+ pre-annealer with steam and cooling device with water and after air) ...and enameling oven, ...take-up. I need please some help how to clean very good the surface of the wire, a solution something because I must guarantee for this wire that can be flattened without problems. And in your post you said that the flattened wire can be used in the production of transformers without problem...why?..if the wire has cracks is this not a problem? can the wire be used in production of transformers? the layer of paper which is wound on the layer of flattened wire protect the transformers against breakdown voltage?
P.S. Sorry for my bad English
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