Re: [TCML] phillips question about wax and more

[Mddeming@xxxxxxx]

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.
 
Matt D.

 
In a message dated 6/11/08 4:34:35 P.M. Eastern Daylight Time,  
fxrays@xxxxxxxxxx writes:

Hi all,
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  
the windings
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.

Frank

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
>ASRG.
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