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Re: [TCML] HV tolerant EMI filters?

> On Jun 21, 2017, at 5:45 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
> Hi Bill,
> I also toasted an EMI filter early on in my coiling career.  I performed a
> thoughtful analysis of how I had it wired, and discovered that I had it
> hooked up incorrectly.  It's not at all obvious what the right way is.  I
> wrote up the wrong and right ways with an explanation of what makes each
> right or wrong.  Please see http://www.laushaus.com/tesla/emifilter.htm.
> How did you have yours hooked up?

Hi Gary, thanks for the thorough reply. On the assumption that the load was
the expected to be the RFI generating source I had the NST connected to
the load terminals, and the Line going to the line. Actually, the filter was not
between the NST and the variable, but right at the line, after the circuit breaker.
Failure mode was to open completely on one side and very high resistance
on the other.

I suspect having the safety gaps set too far apart was a contributing factor,
although they were set correctly for a different main gap. The new RQ type
gap actually needs more gaps / spacing to fully charge the cap, I’m not even
getting full performance out of the machine.

Thanks for your reply and that informative link.
 - B(G)L

> Regards, Gary Lau
> On Wed, Jun 21, 2017 at 1:04 PM, Gomez <gomez@xxxxxxxxxxxx> wrote:
>> As part of my effort to build an “ultimate” (to me at least) control panel
>> / primary supply
>> for “My Last Tesla Coil”, I included a corcom type EMI filter in the
>> supply side of the line
>> to try to make the coil as “friendly” a load as possible.
>> During tune up during a recent demo, the primary took a strike, the
>> safety gaps didn’t
>> fire (that I noticed, it was all over in the blink of an eye) and somehow,
>> HV nastiness
>> got past the Terry filter, NST, and torched the filter.
>> During the event _something_ made brief arcing flames inside the panel
>> visible through
>> the ventilation grill, but there’s no side of physical damage to anything.
>> I’ve been scratching my head trying to find the path. All components, the
>> NST, the Terry
>> filter, appear fine.  There’s a fine dusting of what looks like smoke
>> residue on some
>> cables, but I’m damned if I can find any arc or penetration marks
>> anywhere.  The
>> ground of the coil was to earth and isolated from the supply/panel ground.
>> It seems to me that the strike’s HV had to pass through the Terry filter
>> and the NST
>> to get to the corcom, but then I would expect damage to those parts.
>> Curious.
>> I have some ideas to improve the situation for next time, but I’m now
>> wondering
>> whether anyone makes any EMI/RFI filters with rather high voltage peak
>> ratings.
>> My initial web searches from the usual suspects haven’t turned up any.
>> I suppose I could put a monster industrial MOV unit at the filter, but
>> that seems like
>> a bandaid which will just wear out eventually, the way MOVs tend to do.
>> Ideas?
>> - Bill “Gomez” Lemieux
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