RE: [TCML] Terry Filter Gound

[Quarkster <quarkster@xxxxxxx>]

Dex -
 
Remember that in "real-life" operating conditions powering a luminous tube, a NST only operates at full output voltage for a few seconds every time it is turned on. As soon as the gas in the tube ionizes and begins to conduct, the output voltage of the NST drops to a much lower value than its "nameplate" (open-circuit) voltage.
 
A high-quality NST should be designed and built with good enough safety factor in the secondary insulation that it can survive for a reasonable length of time at full output voltage (for example, with a broken luminous tube), but that is not its "normal" operating condition.
 
Unless you have an unlimited supply of "free" NSTs, I strongly recommend a Terry filter for any NST that is powering a Tesla coil.
 
Regards,
Herr Zapp
--- On Wed, 3/11/09, Dex Dexter <dexterlabs@xxxxxxxxxxx> wrote:

From: Dex Dexter <dexterlabs@xxxxxxxxxxx>
Subject: RE: [TCML] Terry Filter Gound
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Date: Wednesday, March 11, 2009, 11:41 AM

How much peak voltage a normal 15kv,60 mA NST tolerates?
If the spark gap in parallel is set to fire at 18-20 kV the NST is safe without
filter?

Dex 

--- Gary.Lau@xxxxxx wrote:

From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Cc:
Subject: RE: [TCML] Terry Filter Gound
Date: Wed, 11 Mar 2009 16:52:40 +0000

It probably comes down to how robust your transformer is, insulation-wise,
rather than what power level it generates.  Could also be that a 15kV NST needs
protection more than a 4kV NST, as there is less margin in the insulation.  But
in more practical terms, I think folks tend to use a filter if they feel their
transformer is not something they can afford to loose.  If you've got a
shelf full of NST's waiting to be used, you're probably not going to
bother with a Terry filter.  MOT's are both low on the voltage scale and
relatively plentiful, so unlikely candidates for filter protection, despite
being at least 1000W.

A more interesting question would be - at what power level should one use a
dedicated RF ground.  But I gave no good advice for that one!  Probably depends
on whether you have a house full of critical, expensive medical electronics.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Dex Dexter
> Sent: Wednesday, March 11, 2009 7:02 AM
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] Terry Filter Gound
> 
> 
> What power levels requires filter for a spark gap tesla transformer?
> Do all 500-1000 W powered coils require filter?
> 
> Dex

<snip>
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