RE: [TCML] Line Filter Rating

["Lau, Gary" <Gary.Lau@xxxxxx>]

Thank you Jim for a much-needed sanity check!  There is an awful lot of advice out there suggesting that massive ground wires are needed, probably driven from a lower inductance (?) perspective than a current carrying one.

I'm curious about your report of killing an NST in a coil that was not properly grounded - I've not heard of such a failure mode before.  It's clear that without a proper ground, that the RF return path will occur _through_ the NST and into the mains wiring.  Do you know just what it was in the NST that failed?  Primary to core insulation?

Commercial EMI filters are actually not very good at attenuating the relatively low resonant frequencies that most coils operate at.  Their main application is to attenuate much higher frequencies.  This isn't to say that EMI filters are worthless, as TC's generate a lot of harmonics; just not what many of us think they are.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of jimlux
> Sent: Friday, August 01, 2008 12:06 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Line Filter Rating
>
> bunnykiller wrote:
> > Hey John...
> >
> > Since you are imploying a 9/30 NST as the power supply, you have a few
> > options as far as grounding. In preferential order here they are
> >
> > 1. ( expensive) pound about 10  8' copper rods into your lawn and
> > connect all of them together with 1/2" thick solid core copper wire :)~
>
> Not only expensive, but sort of massive overkill...  On the other hand,
> if your coil magically calls down lightning strikes, then you're all set.
>
> > 2. ( affordable) drive 1  8' copper clad steel rod into the ground and
> > connect with 12 ga. wire
>
> For a 9/30?  How long is that 12ga wire? Unless the ground rod is right
> underneath the coil, I don't know that this is much better than just
> laying the wire on the ground, sans rod.
>
> > 3. ( cheaper)  drive 2' of steel pipe with 12 ga. wire attached
> > 4. (really cheap) use a counterpoise made of chicken wire approximately
> > 3X3 feet attached to the base of the secondary with 10 ga. wire
>
> You might go to 4x4 ft.. and AWG 16 wire is a lot easier to handle, and
> will certainly handle the not too massive current from a 9/30  (after
> all, the RMS current in the PRIMARY is 30mA, tops, and the RMS current
> in the secondary is probably less than 1 mA.  Peak currents are higher,
> sure, but the secondary is wound with a good fraction of a mile of
> fairly fine wire, so the extra loss from a couple feet of AWG 16 as
> opposed to AWG 10 is negligible.
>
>
> > 5. ( really cheap now) spread alot of salt on the living room carpet and
> > soak well with water, attach wire to plumbing or gas pipe and lay wire
> > on carpet or better yet in soaking wet carpet pad...   not the best idea
> > but possible with potential dangers involved ( do not touch toroid while
> > barefoot on the wet carpet if using this method)......
>
> Or, invite a crew of incontinent beer drinkers over and get a barrel of
> beer...
>
> Or all the puppies from 101 Dalmatians?  (prior to house training)
>
>
> > 6. dont ground at all but be prepared for transformer/cap failure or
> > racing arcs on the secondary...
>
>
> Oh yeah.. an excellent way to kill your NST, if the secondary doesn't
> catch fire first..
> been there, done that..

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