RE: NST Life Expectancy

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

Original poster: "WIZZARD . by way of Terry Fritz <teslalist-at-qwest-dot-net>" <pbobyk-at-hotmail-dot-com>




>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: RE: NST Life Expectancy
>Date: Fri, 13 Jun 2003 11:03:41 -0600
>
>A properly constructed "Terry filter" includes safety gaps that have been 
>adjusted to fire just over the NST's open-circuit voltage, and a string of 
>MOV's.  Did your filter have these elements?

Yes the circuit was functioning.
Read next statement.

>Your statement that "my new RQ gaps were opened full.." would seem to 
>indicate the cause of the problem.  Safety gaps and MOV's are like speed 
>limit signs and speed traps, and opening the gaps is like putting the gas 
>pedal to the floor.  Live fast, die young.

You are absolutely correct. It turns out the gap was large enough that the 
voltage could have peaked to 20 KV and not the "proper" 15 KV max. I have 
also changed the variac tap to 120 Volt max instead of 140.

>The water condensation may be a by-product of the fire resulting from your 
>NST's internal arcing, or it may be a remnant of a harsh pre-coiling life 
>in an outdoor sign, difficult to say now.  If the latter, this may have 
>been a factor in the unit's early demise.

I found the high voltage lead almost on top of the neutral lead under the tar.
After removing the tar in this area the transformer worked again... WHEW.


>Gary Lau
>MA, USA
>
>
>Original poster: "WIZZARD . by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><pbobyk-at-hotmail-dot-com>
>
>My 4" coil and had one of the NST's die.
>I suspect my protection circuit was the cause.
>I made a Terry filter and put it on my remaining NST.
>I believe the second transformer has now failed.
>I'm new to this game but I think a transformer should last more than a
>couple minutes of operation.
>What is the normal life expectancy of an NST?
>
>The second 15KV/30mA transformer was doing great. The coil was tuned and my
>new RQ gaps were opened full..
>I could hear some internal arcing inside the NST case and could smell a
>burning smell.
>I pulled the top off the transformer immediately and some smoke/steam came
>out as I lifted the cover.
>I could see the tar had cracks just like the last one that failed. This
>time there was a small hole where what looked like water had condensed
>around. The liquid was also condensed on the top that I lifted off. The
>transformer case was quite warm if you grabbed the case.
>What is happening?
>How can I stop this.
>
>A quickly going broke coiler... LOL!