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Original poster: "Hajdrowski, Leo T." <leo.hajdrowski@xxxxxxx>
Hi Dr. Resonance,
I guess what you're saying is the consensus of everyone answering this
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Tuesday, July 04, 2006 6:33 AM
Subject: Re: Capacitor
Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>
These blue "glassmike" caps will not work for RF Tesla coil duty ---
they are DC filter capacitors and will fail in short order at RF
frequencies. You need extended foil pulse duty rated capacitors designed
for RF (high freq alternating currents) work.
>Original poster: "Hajdrowski, Leo T." <leo.hajdrowski@xxxxxxx>
>The capacitor I'm using is made by Plastic Capacitors, Inc. of Chicago.
>It's a type 'OF' HV Filter - Glass Container. It's a hermetically
>sealed plastic dielectric with mineral oil. It's 9" long by 1 5/8"
>It's .02MFD and 30KVDCW.
>Yes, the other X-Ray capacitors were .11MFD in parallel at 90KVDC! Very
>I adjusted the spark gap to fire continously with the greatest gap
>spacing - I'm not using any additional air for quelching. I tuned the
>primary by adjusting the tap that produces the longest secondary spark.
>One end of the secondary coil wire goes to the top torroid and the
>other end to a pipe pounded into the ground.
>I just don't get that HV high frequency corona; as I said before, the
>output looks just like a step-up transformer!
>From: Tesla list [mailto:tesla@xxxxxxxxxx]
>Sent: Monday, July 03, 2006 11:51 AM
>Subject: Re: Capacitor
>Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>The next thing that I would look at is the primary coil tuning followed
>next by the spark gap design. Have you tuned the primary coil to the
>secondary for maximum output spark length? Also, how well built is your
>spark gap? Does it pro- perly and efficiently dissipate the generated
>heat to allow for proper and complete quenching? Also, I think Bart
>Anderson mentioned in previous post that he was assuming that your
>stated ".2 uFd" rating of your 2 caps was a misprint and that you
>actually meant to say that they were rated at ".02 uFd".
>Is this correct?
>The 30 kV DC rated capacitor can also be ran on AC although not at the
>full rated 30 kV in AC volts. What's more important is whether ot not
>your capmis rated for pulse discharge duty or for filtering duty.
>Filter cpas aren't of much use for Tesla coils as they are not designed
>ruggedly enough for the very high discharge currents generated by the
>rapid charge/discharge cycles of Tesla duty. Filter caps will quickly
>overheat and may catastrophically rupture from internal heat buildup in
>a Tesla coil.
>----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
>Sent: Monday, July 03, 2006 10:46 AM
>Subject: RE: Capacitor
> >Original poster: "Hajdrowski, Leo T." <leo.hajdrowski@xxxxxxx> Hello
> >David, As you suggested, I replaced the (2) big X-Ray capacitors with
> >(1) .02 MFD, 30KVDCW capacitor.
> >I still get the same 6-8" spark w/o any corona on the torroid!
> >Since the capacitor is rated as DC, can I run AC?
> >-----Original Message-----
> >From: Tesla list [mailto:tesla@xxxxxxxxxx]
> >Sent: Tuesday, June 27, 2006 3:06 PM
> >To: tesla@xxxxxxxxxx
> >Subject: Re: Capacitor
> >Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx> Leo, Larger
> >than resonant (LTR) capacitance is a good thing, especially for NST
> >powered coils and even more so for NST powered coils that are
> >equipped with a synchronous rotary spark gap (SRSG). However, there
> >are limitations to this and .44 uFd is WAYYY too large of a primary
> >ca- pacitor for a 15/60 NST powered coil. I believe around
> >.02 uFd is a resonant capacitoance for a 15/60 NST trans- former and
> >resonant size is considered optional for a stationary gapped NST
> >powered coil and 3x resonant for an SRSG NST coil. So with your
> >stationary gap,
> >.04 uFd would be about as big as you would want to go with your coil.
> >Your capacitor is about 11x too large and even if you were to series
> >2 caps instead of paralleling them, you'd still be at .11 uFd which
> >would still be nearly 3x to large! You should probably opt for the
> >942 series snubber capacitors (.1 or .15 uFd each at 2000 volts) and
> >series-parallel how ever many you need to get the correct total
> >capacitance with a multiple-mini capacitor (MMC).
> >Also, I believe you'd be better off to take out your rectifier and
> >run AC with this type of coil. DC powered coils require proper
> >filtering or else you're just running a half chopped off sine wave
> >instead of true DC and this would not be an efficient way to operate
> >I would also consider building a better multiple section stationary
> >spark gap with forced air cooling to aid in quenching or if you're
> >willing to take on an additional constructional challenge, go for a
> >David Rieben
> >----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: <tesla@xxxxxxxxxx>
> >Sent: Tuesday, June 27, 2006 12:35 PM
> >Subject: Capacitor
> > >Original poster: "Hajdrowski, Leo T." <leo.hajdrowski@xxxxxxx> Hi
> > >All, One quick question.
> > >I just finished helping my son build a coil:
> > >15 kv, 60 ma nst with full wave rectification Secondary 10.5" x 30"
> > >#22GA wire Primary 3/8" 10 turns copper tubing flat coil - 1/2"
> > >spacing between winds 1" spacing between primary and secondary
> > >First windings of secondary approximately 1" above primary.
> > >Stationary spark gap with 1/4" spacing 20 amp variac 30" dia.
> > >Torroid
> > >(2) .22uf 90KV capacitors in parallel (They came from an X-Ray
> > >machine and are about 4" dia. X 18" long).
> > >We only get about an 8" spark and no corona.....it doesn't appear
> > >to be high frequency, more like a step-up xfmr.
> > >Is too much capacitance bad?
> > >Thanks...Leo