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Re: [TCML] Insulating a MOT
On 11/07/2012 04:56 PM, mrapol@xxxxxxxxxxxx wrote:
. Has anyone ever tried spray-on rubber undercoating as
I have not used undercoating as a high voltage insulator, but glancing
at the MSDS of one particular product, "Rustoleum Undercoating"
reveals that the product contains bitumen.
Checking the wikipedia page for bitumen
(http://en.wikipedia.org/wiki/Asphalt), we learn that, "Most natural
bitumens contain sulfur and several heavy metals, such as nickel,
vanadium, lead, chromium, mercury, arsenic, selenium...."
So the bitumen in this particular brand of undercoating might have a
metallic content, but whether or not it might be a problem in a MOT
running at 60Hz will be the question (I do not know the answer to this).
Now here is another brand of undercoating (Tectyl 127cg -
which actually is an insulator, with a dielectric strength of 800V per
dry mil (0.001 inch).
So, it might depend upon exactly which undercoating product you end up
using; the Tectyl product is certainly rated as an insulator, while the
Rustoleum product will require you to run an experiment to see if it
Personally, I would try to source another MOT with better insulation,
or, barring that, I would pot the one you have in paraffin (I have my
NSTs potted in wax, as it has a dielectric strength of between 200V to
300V per mil). Paraffin has a very low viscosity at the temperature of
boiling water, which gives it the ability to penetrate pretty well; not
as well as oil, obviously, but it might be good enough depending on how
deep in you have to go (you can also preheat the MOT core to help keep
the wax liquid while it penetrates).
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