High Voltage insulating resin - Page 1
Forum section: electronics / general

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 04, 2021, 02:35:32 pm
content: HelloI want to use a high voltage insulating resin for several high voltage transformers (10kV and 20kV and above) but I don't how I should choose a proper resin:Thanks

author: David Hess
author_rank: Super Contributor
timestamp: August 04, 2021, 04:49:06 pm
content: Wax may be an easier to use alternative. There are specific was formulations intended for potting.

author: TimFox
author_rank: Super Contributor
timestamp: August 04, 2021, 05:02:59 pm
content: With any potting material, be careful to eliminate bubbles from the final state. Normally, this is done by pumping a vacuum above the "pot" while the material is still liquid.Wax is a traditional material: note that it shrinks drastically at the phase transition between liquid and solid as it cools.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 04, 2021, 05:16:26 pm
content: Beats me. Have you checked mfg websites (e.g. 3M)?As I recall, the stuff used in FBTs is extremely hard; probably mineral filled (silica or otherwise?).And yeah, you definitely want a vacuum pot for that. You can verify quality in a couple ways, like hi-pot for isolation barriers, but also partial discharge for breakdown around windings -- a pocket of air exhibiting breakdown, is detectable as high frequency (impulsive) emissions, when the part is excited (preferably by a nice smooth sine wave).Tim

author: David Hess
author_rank: Super Contributor
timestamp: August 04, 2021, 07:34:22 pm
content: One reason I would avoid random epoxy potting compounds is that some have horrible dielectric loss even without leakage. Tektronix had a horrible time with this when they initially changed from wax to epoxy.Quote from: TimFox on August 04, 2021, 05:02:59 pmThat is why I mentioned that there are specific wax mixtures used for potting.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 04, 2021, 09:59:34 pm
content: Huntsman and LORD are two companies that produce very high quality 2 component resin for high voltage insulation.As others have mentioned, for a good high voltage insulation, you need to pot under vacuum.One important reason for the vacuum is to get all humidity out of the system before potting, otherwise the humidity can be a big factor in the insulation properties.

author: TimFox
author_rank: Super Contributor
timestamp: August 04, 2021, 10:16:24 pm
content: A fundamental reason to avoid bubbles is a not-obvious electrostatic result. In a parallel-plate geometry, the E field between the plates with a uniform dielectric (or vacuum) isE=V/x, wherexis the spacing. If almost all of the gap is filled with a dielectric with constantk, but a thin layer of air (k= 1) occupies a small region, the equilibrium value of the field in the dielectric is unchanged, but the field in the air gap is increased by the factork, which is bad since the breakdown field in air is probably less than that of the dielectric.

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 07, 2021, 02:08:54 pm
content: Quote from: TimFox on August 04, 2021, 05:02:59 pmQuote from: HighVoltage on August 04, 2021, 09:59:34 pmI want to see some videos about it, I want to build a simple one in my room! I'm alive with my instruments!

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 08, 2021, 06:24:22 am
content: Quote from: David Hess on August 04, 2021, 07:34:22 pmcould you please show me a good wax and a mixer?I found an epoxy with the below specification:Dielectric coefficient= 4.6Viscosity= 1080 CentipoiseDensity= 1.47 gr/cm3Pressure resistance= 742 kgf/cm2Volume resistivity= 5e14 Ohm.cm3Surface resistivity= 9.8e13 OhmHeat Deflection Temperature= 50 'Cis it a good insulating Epoxy?

author: David Hess
author_rank: Super Contributor
timestamp: August 08, 2021, 05:21:24 pm
content: Quote from: xzswq21 on August 08, 2021, 06:24:22 amI do not know anything more than you can find online. I know that it takes more than pure paraffin wax.

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 23, 2021, 06:29:54 pm
content: I want to buy a vaccum pump to remove air bubble in an electrical insulating resin, target pressure as you recommended me should be around 10-50mBar,internal volume of my Vacuum oven is 0.45 cu.ft. Int or 12.7 Liters (inside chamber dimensions :8"x8"x12”)now I have two choices for the vacuum pump:"Fisher Maxima C plus M2C" and "Welch 8890A"Fisher M2C:https://www.fishersci.com/shop/products/fisher-scientific-maxima-c-italics-begin-plusitalics-end-vacuum-pump/0125777https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/scientific/brochures-and-catalogs/brochures/fisher-scientific-maxima-c-plus-vacuum-pumps-brochure.pdfWelch 8890A-55:https://www.idealvac.com/NEW-Welch-8890A/pp/P104262https://www.idealvac.com/files/brochures/Welch_8890_Owners_Manual.pdfwhich one is better for my application? as you see the internal volume of the oven is small.I will buy a used one, but the Welch 8890 has an air lock system! it means:QuoteThanks

author: BrokenYugo
author_rank: Super Contributor
timestamp: August 23, 2021, 07:24:26 pm
content: I highly doubt you need a $2500 scientific vacuum pump for this, a cheap AC service vacuum pump should do.

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 23, 2021, 07:31:55 pm
content: Quote from: BrokenYugo on August 23, 2021, 07:24:26 pmthe price of a used one is only $100-$200

author: David Hess
author_rank: Super Contributor
timestamp: August 23, 2021, 08:50:05 pm
content: A cheap AC service vacuum pump is more than good enough. A regular air compressor could also be used by attaching to the intake.

author: Vtile
author_rank: Super Contributor
timestamp: August 23, 2021, 10:04:45 pm
content: Shellac is one natural resin used in the past as electrical insulator.. Most probably is still used as "secret incredient" in many products.https://electrical-engineering-portal.com/dielectric-strength-insulator-materials

author: Vtile
author_rank: Super Contributor
timestamp: August 23, 2021, 10:41:37 pm
content: Quote from: xzswq21 on August 08, 2021, 06:24:22 amI don't know exactly, but should that be "Dielectric constant"? If not, what is the difference?

author: BrokenYugo
author_rank: Super Contributor
timestamp: August 24, 2021, 01:41:23 am
content: Quote from: xzswq21 on August 23, 2021, 07:31:55 pmI would assume they're cheap used because they have who knows how many hours on them (as I recall, rebuild parts for most brands are expensive or outright never offered) with who knows what sucked through them, probably by careless students*. I'd take a new Chinesium pump over that, e.g. (assuming USA) $150 Harbor Freight 2 stage 3CFM 22.5 micron, or $90 for single stage 2.5CFM 75 micron, even if they're an order of magnitude off spec that's still sub millibar.*Which is probably why they're asking $2500 for what look a whole lot like a $200 AC service pump with a different hardware kit, schools will just pay it.

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 24, 2021, 09:02:04 am
content: Quote from: Vtile on August 23, 2021, 10:41:37 pmYes, it's dielectric constant.what do you think about "3M™ Scotchcast™ Electrical Resin 8N"https://www.3m.com/3M/en_US/p/d/b5005042037/there are a lot of electrical resin from 3M:https://www.3m.com/3M/en_US/p/c/coatings/electrical-resins/is it a good epoxy resin for high voltage transformer potting?

author: HighVoltage
author_rank: Super Contributor
timestamp: August 24, 2021, 09:50:17 am
content: No, this 3M product would not work !It is meant to be applied to motor windings at the end of the winding process.But not for high voltage insulation.

author: xzswq21
author_rank: Frequent Contributor
timestamp: August 24, 2021, 10:21:14 am
content: Quote from: HighVoltage on August 24, 2021, 09:50:17 amI checked most of 3M epoxy resin datasheets but I couldn't find any high voltage characteristic in any of them, actually most of them have 300-400V/mils electrical strength, please help me to find an epoxy resin, some of them are Room temperature curing and some of them are heat curing.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 24, 2021, 10:29:39 am
content: I have used 3M and Loctite products for repair and installation of HV transformers and terminations.E every time i have dont these kinds of job i have got a repair procedure form the manufacturer of the equipment or contacted the support line/email at 3M or Loctite. The support line will give you an recommendation for the best product or products to use .