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Old 4th June 2012, 02:40 PM   #91
Legis is online now Legis  Finland
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I just ordered AC-43 polyester conformal coating in spray bottles, it was the best I could find in Finland.

Some info:

Dielectric strength at 23 C and 50% r.F. kV / mm ≥ 80 kV / mm (2kV per mil)
Surface resistance at 23 C ≥ 10^15 Ω Ω * cm * cm
Surface resistance after 96 h storage in water ≥ 10^12 Ω * cm * cm Ω
Dielectric constant at 23 C between 50 Hz and 1 MHz (1.5 0.5)
Dissipation factor at 23 C between 50 Hz and 1 MHz ≤ 15.10^-3
Loss factor of 0.2 = Point of intersection 200.10-3 ≥ 78 C

It should dry hard but flexible coating, and it's compatible with all other coatings there might be underneath like epoxy based powder coating. I hope it also dampens the stators a little. Capacitive effect is very small due to low dielectric constant value.

Has anybody tried polyester based conformal coatings on esl stators?
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Old 29th June 2012, 05:31 PM   #92
Legis is online now Legis  Finland
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I changed from above mentioned polyester based "real" insulation coating to (solvent thinned) high gloss urethane-alkyd varnish that has 48% solids. Polyester gets too expensive if I ever wanna do a thick coating. I have rolled on couple of layers and it smoothens out guite nicely, looks very glossy (like it's wet when it's not), and applying is way faster than spraying, which I did before. The stuff does not get like epoxy-hard, but stays a bit elastic even though is very hard and durable. Good for curved stators. Hopefully it insulates at least 400V per mil. I will do many many layers.

Regards,

Legis

edit. here's a close-up after 2 coats of high gloss black powder coat, 5 coats of conformal coating and 5 coats of rolled urethane-alkyd varnigh on top (stator is 18 ga). Does not look like much.

Click the image to open in full size.

Last edited by Legis; 29th June 2012 at 05:45 PM.
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Old 30th June 2012, 06:32 AM   #93
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Looks Good !!
Can't wait to hear how they perform.
They should do well !!!!



jer
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Old 2nd July 2012, 11:22 AM   #94
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Hello Legis,

I too have found that the greatest concentration of alkyds solids was available in a furniture spar urethane (Helmsman). I would venture to guess by the appearance of your stators your probably done. How much voltage will you be using, will you be performing an arc test to verify coatings?

Did you roll this on?

I wonder if dipping the stators into urethane may be a viable coating option? I will be exploring this possibility.
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Old 2nd July 2012, 01:41 PM   #95
Legis is online now Legis  Finland
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Quote:
Originally Posted by dochungwell View Post
Hello Legis,

I too have found that the greatest concentration of alkyds solids was available in a furniture spar urethane (Helmsman). I would venture to guess by the appearance of your stators your probably done. How much voltage will you be using, will you be performing an arc test to verify coatings?

Did you roll this on?

I wonder if dipping the stators into urethane may be a viable coating option? I will be exploring this possibility.

Hi, I'm using this stuff: Products in alphabetic order - Tikkurila | Decorative Paints | Products

I plan to use 6-8kV bias on 3mm d/s. Drive voltages max. 5300Vpeak (50Vrms to 1:75 step up). I wish I had a HV wand to test the coating but I quess I just have to apply thick coating and wish for the best.

Yep rolling works very well for me. A foam roller gives the smoothest result. I don't thin the stuff before applying. The roller naturally instroduces visible air bubles into the coating but they can be rolled out by rolling very gently over them couple of times and the bubles disappear. I cannot detect any bubbes with a bare eye from dryed coating.
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Old 3rd July 2012, 01:06 AM   #96
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Legis,

here is a better link to what I used Exterior Clear Protective Finishes | Wood Products it essentially looks like a similar product.

For the H.V. wand you can use your power supply and connect one end to your stator and the other to an insulated handle screwdriver connected by alligator clips, then use tinfoil to drape across the screwdriver to essentially drape across the insulation. I typically do this on the granite counter top with low lighting and the wife nowhere insight, also do this in a quiet room to possibly hear any sizzling.
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Old 3rd July 2012, 01:12 AM   #97
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Legis, I got to tell ya, after looking at your work again I must say it looks great! However, I would strongly suggest that you arc test your panels thoroughly before you begin assembly!

Cheers!
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Old 3rd July 2012, 09:49 AM   #98
Legis is online now Legis  Finland
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Hi, I tried the spark test with the bias supply after 24h cure time. The stator was connected to the step up trafo, and the aluminum coated mylar was biased, aluminum side turned against the stator. At 2,2kV nothing sparked through although the membrane got sucked pretty hard into the stator and the neon bulb blinked like hell. I boosted the bias to current maximum 4,7kV, the neon bulb was lit all the time and I got two sparks near the center area after 10-15 seconds. They left spots on the mylar so I know where they got through.

I quess I just insulate those spots, put on 2 extra layers on the whole panel on both sides, and the panel is quite ready after that... I will also test the front stator with the same method after I have put more layers on it's front side first.

I quess the insulation works quite well.

Click the image to open in full size.
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Old 3rd July 2012, 10:52 AM   #99
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Excellent Job !!!

You are finally on your way to enjoying those beautiful panels again !!!



jer
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Old 4th July 2012, 01:01 AM   #100
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Awesome, I never thought to use aluminium coated Mylar to arc test in that manner, you would certainly hear arcing.

I gather from Jer's comment that this is a rebuild, are those ML curved panels?

Doc.
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