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Re: [TCML] Terry Filter Gound

Hi Dex,
It's true that larger power does certainly create more havoc with hv transients, but also the gap, how the systems running, etc.. make a difference. But to what power makes it a requirement is difficult if not impossible to answer definitively. It's an individual choice. Some transformers are more tolerant than others. NST's are a bit fragile. Most failures are due to a hv winding failure (not all) where the insulation has been punched through causing a shorted turn and usually visible on the outer layers of the hv windings. I prefer to filter NST's. My Pig and Mots I don't filter (just my choice). But with that said, I have even over-volted an NST with a Terry Filter installed (once). A filter is not a full-proof guarantee that the transformer will survive everything, but it does well to filter out most of the garbage.
Regarding filters, I should note that I have noticed less noise on the line with a solid state SISG system than with a traditional spark gap (well, my family has noticed less noise (TV interference mainly). 

Regards,
Bart

Dex Dexter wrote:

What power levels requires filter for a spark gap tesla transformer?
Do all 500-1000 W powered coils require filter?
Dex 

From: "Dex Dexter" <dexterlabs@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Terry Filter Gound
Date: Wed, 11 Mar 2009 03:51:29 -0700



--- bartb@xxxxxxxxxxxxxxxx wrote:

From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Cc:
Subject: Re: [TCML] Terry Filter Gound
Date: Tue, 10 Mar 2009 19:53:16 -0700

I agree and we've said so many times on the TCML.
Bonding is absolutely required (mains to case) in all consumer circuits. But too often, coilers take this "bonding issue" without common sense (applying it to everything). A Tesla Coil is not an appliance. You of course can hook mains ground to the NST case, safety gap, etc. But if you do, you have just directly connected every high voltage nasty transient the coil will spit out (and it will in abundance) to every appliance in your house (Xbox360's, TV's, VCR's, Computers, Washing and Drying machines, Coffee Pot, Clocks, etc..).
Don't do that. Instead, tie RF ground to the Terry filter safety gap and to the NST case. This will direct those nasty transients to the dedicated RF ground. But with that, you must ensure that you never handle your NST with power applied. This is an important safety rule that must be maintained.
If your ok with killing your household items, then sure, hook up mains ground to your NST. No problem. Just don't come crying to me when "bad" happens.
I went though many years never losing anything in my house (because I didn't have a lot to lose I guess). But eventually, I lost a sound card, a video card, and an Xbox360 (just my personal experiences). Others have killed various electronics. "Separating" mains ground from hv garbage in a TC system is highly recommended. One of the best ways to do this is without a direct connection. 

Take care,
Bart

Lau, Gary wrote:

NO!  In a midpoint-grounded NST, the NST case and HV winding midpoint connect to the RF ground, same place as the Terry filter ground.  The mains ground goes only as far as the Variac case - things that one would reasonably touch while the coil is operating.

When an NST is used to power a neon sign, it's reasonable to expect that one might touch the NST case, so it needs to be tied to earth ground for safety.  But as the NST case in a Tesla coil circuit must be tied to RF ground, you can't have it both ways, so don't touch the NST case while your coil is powered up.

Schematics of my coils here:  http://www.laushaus.com/tesla/myschematics.htm
And Terry filter stuff: http://www.laushaus.com/tesla/protection.htm

Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of James Howells
Sent: Tuesday, March 10, 2009 3:30 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Terry Filter Gound

The NST mains ground goes to mains earth
Every thing from the HV side including the safety gap Tery filter goes to Actual
earth / ground / stake in the soil
________________________________
From: Simon Dodd <simon@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tuesday, 10 March, 2009 19:08:54
Subject: [TCML] Terry Filter Gound

Hi Guys,

I'm a little bit confused about the ground from the Terry Filter.  All the schematics
and pictures I have seen have indicated connecting the ground of the safety gap to
RF ground and also running it back to the NST ground.

However everything else I have read has stated expressly not to connect the NST
to the same RF ground as the Tesla coil.  The only thing I can think of is to not
connect the NST to the mains earth and keep it only on the RF ground.

Thanks



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