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Re: [TCML] phillips question about wax and more
Polyurethane varnishes did not exist during Tesla's lifetime.so he could not
have commented on them. I fully agree that the varnishes and shellacs of
1899-1900 were inferior for high voltage work.
In a message dated 6/11/08 4:34:35 P.M. Eastern Daylight Time,
Beeswax and rosin was found to be the "best" insulating medium for a
Tesla coil, such as a pancake. Tesla himself found that to be most effective.
All insulating mediums have different characteristics at different
frequencies, just like capacitors of different materials.
Tesla stated shellacs and varnish are not good insulators for Tesla
coils but that is all we have today.
Trying to find beeswax or rosin in large quantities at reasonable
prices is not easy.
The closest substitute are toilet rings for the beeswax. Of course
that is new rings.
Now insulating medium for a HV transformer can be a variety of
materials as discussed in this group.
Re-potting a NST without shunts is mainly for heat transfer as you
are now operating a NST up to 10 times its original rating, you need
to take the heat away.
Now, when you re-pot a transformer, or motor or even a capacitor,
there will always be tiny air pockets in and around the windings due
to surface tension of the insulating medium. Oil is better at filling
those pockets and wax, varnish, tar, and etc is worse.
These pockets of air are a potential source for arcing due to reduced
insulation resistance in those areas.
Vacuum impregnation is the only way to remove the air pockets and
insure the system is at its best for insulation.
As stated, not all of us have means to draw a vacuum on our devices
but most of us have simple wood working tools.
Pre heat the transformer before pouring the medium, this is very
important for wax/ tar as the cold iron will cool the wax/ tar and
form air pockets preventing the wax/tar from effectively insulating
Take a vibrating sander and remove the paper, put the pad of the
sander on the case of the transformer, coil, cap or etc when you are
pouring the wax, tar, oil or etc. The vibrations will help "pop" the
air bubbles and get the insulating medium more effectively
distributed into the windings or plates.
Not as good as drawing a vacuum but works well and simple.
Now, using a ASRSG, there will be periods where the NST is "unloaded"
and higher voltages will be across the windings. NST's do not like to
run open circuited at all, they are not insulated to handle the open
voltage for long periods of time.
As your transformer gets older, it is more susceptible to shorting
out as the insulation starts to break down.
This could be a possible reason for your NST dying with a ASRSG.
At 10:56 PM 6/10/2008 -0500, you wrote:
>While we're on the topic of NSTs, ASRGs are pretty bad for them right?
> It seems that my NST keeps shorting, and I think it's due to the
>Tesla mailing list
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