Author Topic: Degassing of Dielectric Oil Using High Vacuum.  (Read 258 times)

Offline Patrick

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Degassing of Dielectric Oil Using High Vacuum.
« on: November 07, 2019, 04:32:39 AM »
Ok I'm getting ready to make a serious go at it. Some questions I have would be temp, duration, and pressure Im continuing research but not sure.

The goals for this apparatus are to degas oils and epoxy, vacuum draw and fill caps and transformers with epoxy, oil or 2 part silicone. Side projects would be to verify capacitors and mosfets at the equivalent to 100k feet at high and low temperatures.

pics of the apparatus:
https://i.imgur.com/1iv0TPR.jpg
and:
https://i.imgur.com/g2EIR0N.jpg
pdf: Attached

I'm making a stainless steel screen like layer-cake to act as Raschig rings. Which will be lifted into and out of the oil being degassed by stepper motor and scavenged 3D printer vertical axis parts. All parts will be thoroughly sonic cleaned including the motor. Ive found this and similar information that suggest .1 to 5 torr or thereabouts is a good starting point.

ill verify a samples breakdown potential before and after treatment in 6 hour intervals i guess to graph a trend indicating the end of improvement for each oil type.

I don't have access to the purpose made dielectric oil like Shell Dialla AX, but I use food oil mostly anyway.

The capacitors in the clear cube were at 100k feet for balloon testing.

.
« Last Edit: November 07, 2019, 05:30:41 AM by Patrick »

Offline davekni

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Re: Degassing of Dielectric Oil Using High Vacuum.
« Reply #1 on: November 08, 2019, 03:52:11 AM »
Do you have oil for your vacuum pump?  That would likely be much better than food oil.  Mineral oil is often available at local stores - used as an occasional laxative or as baby oil.  (Baby oil is just mineral oil with perfume added.)  Food oils have polar groups, which will cause higher dielectric loss, more water absorption, and likely lower breakdown voltage.  Also, food oils (unless 100% saturated) have C=C double bonds, so will chemically degrade faster.
David Knierim

Offline Patrick

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Re: Degassing of Dielectric Oil Using High Vacuum.
« Reply #2 on: November 08, 2019, 07:02:46 PM »
mmmm Ive looked at this before, back on 4hv. ill have to run a table and chart of all oils and properties, now I have the equipment to do so. Only Corn oil seemed to be catastrophically unusable right from the get go. We were trying to stay away from hydrocarbon oils.

Soy bean oil is used in 50kV+ main line transformers which run for decades. So we always discussed this, but now we'll know. Aging is always a concern, but for me 2-3 years is fine.

We always thought "Envirotemp"was soy bean oil with green dye and 1 or 2 % additives that we hobbyists probly dont need.
https://www.cargill.com/news/releases/2013/NA3082422.jsp
« Last Edit: November 08, 2019, 07:07:15 PM by Patrick »

Offline DashApple

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Re: Degassing of Dielectric Oil Using High Vacuum.
« Reply #3 on: November 08, 2019, 10:16:14 PM »
I have ever only vacuumed a transformer under oil to remove the trapped air within the windings and not tried to degas the oil its self so not sure if this reply will be helpful

I used HV transformer mineral oil and ran it direct from the vacuum pump for 6 days

I believe there are some baby oils that are pure mineral oil without any additives ?

Offline davekni

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Re: Degassing of Dielectric Oil Using High Vacuum.
« Reply #4 on: November 09, 2019, 03:20:09 AM »
Interesting information about Cargill's FR3 oil derived from soybean oil.  Looks like I'm way out-of-date!  I wonder how much modification is done to the soybean oil.  They mention paper insulation lasting much longer.  Perhaps that's tied to the polar molecules in paper bonding to the polar parts of the oil.  (The dielectric dissipation caused by the polar parts of the oil would be of no issue at line frequency, only for high-frequency use.)

Cargill mentions FR3's biodegradability.  To me, that suggests the double-bonds (unsaturation) are likely still present.  Guess that's not an issue as long as the air is thoroughly removed.

Thank you for the update.  I stand corrected.
David Knierim

Offline Patrick

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Re: Degassing of Dielectric Oil Using High Vacuum.
« Reply #5 on: November 09, 2019, 06:54:09 AM »
I stand corrected.

Im not saying thats fact just that was an example i found from the $$$ industry.

we need this info too but i cant find any open-source or open-method examples in several years of searching. Just random YouTube vids showing a poorly wound and insulated flyback in a food container of oil.

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Re: Degassing of Dielectric Oil Using High Vacuum.
« Reply #5 on: November 09, 2019, 06:54:09 AM »

 


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