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Re: 3rd harmonic trap. Apology

Original poster: "Jolyon Cox" <jolyon@xxxxxxxxxxxxxxxxxxxxxxxx>

In understanding that a little knowledge is a dangerous thing, I acknowledge
that at thew time of my writing  I was not in full possesion of the facts,
not least that I have not yet read Paul Nicholson's work and until that time
it is beholden upon me to read a little more and comment a little less.

My purpose in asking about the third harmonic trap was as an alternative to
Terry's bandpass filter (no offence intended!) my thinking being that  third
harmonic oscillation was the cause of  excessive primary currents cause
destruction of  the IGBTs in a DRSSTC in the event of it arcing to the
primary; I now understand in this line of reasoning I may have been mistaken
and need to read more.

My sincerest apologies,

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, March 25, 2005 3:28 PM
Subject: Re: 3rd harmonic trap

> Original poster: "Gerald Reynolds" <gerryreynolds@xxxxxxxxxxxxx> > > Hi Terry and all, > > If I remember right, didnt Paul Nicholson describe the higher resonant > modes of the "1/4" wave secondary and a third harmonic was not among > them. If this is the case, then why would this be an issue?? > > Gerry > > >Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx> > > > >Hi, > > > >I am not sure "why" filtering the 3rd harmonic is needed. But one could > >put a high-Q LC filter in parallel and short that frequency out on the > >primary. But you would still get the 3rd on the top voltage and secondary > >system so I am not sure "why".... > > > >Filtering the secondary would be hard since it is not obvious how one > >would do it. The primary is already a real good high-Q filter, so the 3rd > >harmonic is very low. Simply the natural switching is responsible for a > >lot of that and you are not going to stop that much unless you run CW. > > > >Filters like the protectors in the note could be modified. Just an LC > >circuit.... They can be made very high Q!! and high current!! Adding > >such a parrallel LC might do odd things like get other resonant > >frequencies going.... > > > >In the case of the protectors, they are in series and far off values so > >they just blend with the secondary (even though there are three inductors > >and three caps, it is still second order). They normally have very little > >effect. > > > >Cheers, > > > > Terry > > > >At 01:51 PM 3/23/2005, you wrote: > >>On 23 Mar 2005, at 8:38, Tesla list wrote: > >> > >> > Original poster: "Jolyon Cox" <jolyon@xxxxxxxxxxxxxxxxxxxxxxxx> > >> > > >> > if a 3rd harmonic band-reject filter or "trap" would not work, how > >> > about a band-pass filter tuned to the fundamental of the TC? Would > >> > this not a correct description of the of circuit described in the > >> > following? http://drsstc.com/~terrell/notes/DRSSTCprotec.pdf > >> > >>Has the scheme actually been tried? What is the effect on tuning of > >>the extra inductors capacitors? I thought a Tesla Coil was a bandpass > >>filter of sorts. > >> > >>Malcolm > > > > > > > > >