[TCML] Line Filter Rating
Gary.Lau at hp.com
Sat Aug 2 12:31:25 MDT 2008
Part of the problem is that the problem definition is not well understood - what is it exactly that we need to filter out? What is the symptom of the problem?
Is it high voltage transients that may damage household appliances? If so, is it a simple spike, or is it a HF burst?
Is it mainly the fundamental frequency, or is it higher frequency overtones? Is the problem one of fearing damage to things, or is it interference with phones, TV, etc?
Another problem is that we have no way to measure the effectiveness of anything. Given that we can't even agree on what the problem is, that's not surprising! Just saying that I've used so-and-so and I've not smoked any appliances in all my years of coiling carries no weight in my book.
I put an EMI filter and ferrite EMI filter on my coil, only because it was easy and cheap to do so and it didn't harm performance. There's no doubt that radio reception in my house is affected, and will likely be regardless of what I use, but I don't often listen to radio or watch TV while running my coil ;-) I run my coil so infrequently that I'm not overly concerned with affecting neighbors. If appliances and electronics died coincidentally with running my coil, I would probably take a closer look at transient filtering, but it's just not been a problem, so I'm content with the status quo.
Regard, Gary Lau
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of David Nelson
> Sent: Friday, August 01, 2008 9:59 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Line Filter Rating
> You say that comercial line filters are not designed for the frequencies of
> tesla coils. Should someone design one that is more appropriate?
> Dave Nelson
> ----- Original Message -----
> From: "Lau, Gary" <Gary.Lau at hp.com>
> To: "Tesla Coil Mailing List" <tesla at pupman.com>
> Sent: Friday, August 01, 2008 10:51 PM
> Subject: RE: [TCML] Line Filter Rating
> 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
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