Re: Necessity of NST Protection Filters and Safety Gaps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Brett Miller <brmtesla2-at-yahoo-dot-com> 


<SNIP>
I don't use protection networks as well on my NST powered tesla coils. I
have 4kV/32mA, 6kV/30mA, 12kV/60mA, and a 15kV/60mA
NSTs which have all been used in both static gap and synch rotary spark gap
tesla coils for hours and hours of use. No protection networks, and
no protection spark gaps. Although NST filters and safety gaps are
recommended, they aren't absolutely necessary.

It is a higher risk running without them, but how much higher is hard to
say. If the risk was really that high, i would really expect at least one
of the
above NSTs to fail especially considering how much use they are getting.
For one demonstration, I ran my 15kV/60mA NST for about 8 hours
straight (at about 20% duty cycle - 1 minute run-time, 4 minute rest period
waiting for next group to see exhibit). Thats a lot of use in one day!!!
That NST was darn hot all day!!

I mostly use Franceformer NSTs. I wonder is there are major diffe! rences in
the construction of various NSTs from manufacturer to manufacturer making
one type more prone to fail than another type.

Dan

Dan,

I use a Franceformer 12/60 on my 6" system with a static gap, usually RESO 
tank cap, and no protection either.  I have a guy locally who can get me 
transformers for free, and a neon sign dealer who will sell used 60ma NST 
to me for cheap <$30.00.  I figure I will be able to cheaply replace the 
NST should it let out its smoke.

So to back up your anecdote with one of my own....I've been using mine for 
around 4 years for average TC hobbiest use (a lot of lab tests and 
measurement) and occasional demos to friends and family.  I have all the 
components for a "Terry Filter" in a tupperware, I just haven't gotten a 
big piece of perfboard to lay it out on yet.  It's a matter of procrastination.

Another thing I've heard on the list over the last 5 years or so (and in 
the archives previous) is that Franceformer and Allanson tend to be the 
most rugged toughest brands of NST for TC use, but I haven't seen an in 
depth study with dissection illustrating why this is so.

-Brett

hot-streamer-dot-com/brett