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Re: Terry filter construction

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Dirk,

At 11:52 PM 10/10/2005, you wrote:
I am now building my Terry filter but I have a couple questions. How much distance must be between separate the parts of different potential? For example, how much distance is required to prevent it arcing over the circuit?

I have kept two things in mind while building these components.

1. Electricity follows path of least resistance.
2. Any distance smaller than safety gap will arc there first. Approximately, how wide should the safety gap be set? 

See the post Gerry just had:

""With the TC primary disconnected from the NST output, set the safety gap spacing to "just not fire" with the NSTs maximum input voltage (ie, 120Vac if plugged directly into the power outlet or 140Vac if using a step up variac). Once set, avoid the temptation to widen the safety gap in order to get longer sparks. During TC operation, you can widen the main gap until the safety fires occasionally (for static gaps).

Gerry R""

Here is a chart of spark gap distances vs. voltage:

http://hot-streamer.com/TeslaCoils/Misc/SGapVolt.jpg

The peak voltage on a 15kV NST is 15000 x SQRT(2) = 21000V. The chart says 20000V can arc 1.75cm (3/4 inch) between sharp points. But the filter is probably only seeing 1/2 that between points in any places so 10kV gives about 3/8 inch. So maybe double that to 0.75 inch. Try to avoid any really sharp edges since they like to corona anyway.


I have posted an image of my Terry filter template. I drew it up in AutoCad, then printed it up. This makes drilling the holes a lot easier and nicer. Do you see any errors in my template design?

<http://www.dirkstubbs.net/terry_filter_template.jpg>http://www.dirkstubbs.net/terry_filter_template.jpg 

Looks fine to me.

Cheers,

        Terry




Thanks
Dirk