RE: question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Loudner, Godfrey by way of Terry Fritz <twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>

Hi Dave

I hope you are using a ballast on your transformer, otherwise the
transformer will be ruined by excessive current. Place a choke in series
with the 120 volt primary. The inductance of the choke will limit the
current flow through the primary during the short circuit at the spark gap.
You can make a choke by shorting the secondary of a mot (microwave oven
transformer) and placing the primary leads in series with the primary of the
potential transformer. When the secondary leads of a mot are connected
together, some of the inductance in the primary is cancelled, allowing a
pretty good and safe current to flow to the potential transformer. If you
want more current to flow to the transformer, then connect the primary of a
second shorted mot in parallel with the primary of the first mot. More mots
can be added in this way, but eventually the inductance of the choke will
become so low that excessive current will flow to the potential transformer.
One or two mots should be sufficient. You will have to accept whatever
inductance is supplied by your choke. Some people have chokes custom made
for a particular power supply, but this approach is very expensive. At
http://www.pupman-dot-com, much information can be obtained by entering the word
ballast into the search engine. 

For short periods, your potential transformer can be run at twice it rated
level. Your transformer can really putout a lot of current, making it a very
dangerous transformer. I would not attempt to place a hand held fluorescent
tube near the secondary of a tesla coil while using such a powerful
transformer. The tesla secondary could become connected to the tesla primary
by a streamer. This could allow lethal currents from the primary tank
circuit to enter your body. Depending on the situation, you could be
electrocuted. Then there will be no more research coming from you concerning
your spiro secondary project. Such demonstrations should be left to the
seasoned professional, who take a calculated risk by considering EVERYTHING
that could go wrong. 

Godfrey Loudner      

 

> -----Original Message-----
> From:	Tesla list [SMTP:tesla-at-pupman-dot-com]
> Sent:	Friday, February 01, 2002 8:47 PM
> To:	tesla-at-pupman-dot-com
> Subject:	RE: question
> 
> Original poster: "David Thomson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
> 
> Hi Godfrey,
> 
> I fully understand what you mean by the Potential Transformer is not
> current
> limited.  I put it on my Tesla coil today.  The spark gap looked more like
> an arc welder.  My single thoriated tungsten, magnetically quenched,
> static
> spark gap just couldn't handle it.  I've been working all day to build a
> spark gap to handle the power.  Fortunately I have eight heavy duty
> military
> electrical contacts made with pure silver rings and some kind of
> non-corrosive, hard electrode.  A preliminary test with this new spark gap
> on my 15KV NST showed a 100% increase in spark length on my secondary
> terminal.
> 
> Yes, the impulse level does seem a bit low compared to others I have seen.
> But I don't intend to see anything over 50KV in the primary so that should
> be OK.  I'm hopeful that this higher current can be put to good use in my
> coils.
> 
> Tell me some safety tips concerning the secondary terminal when the
> amperage
> is increased.  I haven't worked with a high current transformer on a Tesla
> coil before.  Will it still be safe to hold a fluorescent tube to the
> terminal to draw off sparks?
> 
> Thanks,
> 
> Dave
> 
> David Thomson
> dave-at-volantis-dot-org <mailto:dave-at-volantis-dot-org>
> 
> 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Thursday, January 31, 2002 5:58 PM
> To: tesla-at-pupman-dot-com
> Subject: RE: question
> 
> 
> Original poster: "Loudner, Godfrey by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>
> 
> Hi David
> 
> My mistake that I thought you were writing about a primary. You certainly
> have a potential transformer, not a neon sign transformer. A potential
> transformer is not current limited, but a NST is current limited. A
> potential transformer is used to monitor the voltage level of a
> transmission
> line. High voltage is reduced to low voltage for connection with a volt
> meter. The 50kV peak could mean that the insulation can withstand a
> momentary transient of 50kV. Seems a little odd, usually the impulse level
> is 150kV.
> 
> Godfery Loudner
> > -----Original Message-----
> > From:	Tesla list [SMTP:tesla-at-pupman-dot-com]
> > Sent:	Thursday, January 31, 2002 8:18 AM
> > To:	tesla-at-pupman-dot-com
> > Subject:	RE: question
> >
> > Original poster: "David Thomson by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
> >
> > Hi Godfrey,
> >
> > >In your original mailing, you wrote like you were talking about the
> > secondary. But a secondary is not flat,
> >
> > Mine is.  I wound a 27" diameter flat spiral secondary out of 21 gage
> > wire.
> > I'm doing several experiments with flat spiral secondaries.  You can see
> > some of my work with smaller flat spirals wound with three parallel
> wires
> > at
> > my web site www.tesla-coil-builder-dot-com.
> >
> > >What you call a potential transformer just might be a high voltage
> > testing
> > transformer.
> >
> > I'm learning a bit more about this transformer today.  I may have been
> > wrong
> > in stating it was DC output.  The transformer schematic on the cover
> shows
> > a
> > positive and negative terminal with arrows supposedly indicating the
> > direction of current.  But this may simply mean that one terminal is
> > intended to be on the ground side and the output may be AC after all.
> > It's
> > an older transformer made by Westinghouse and I have much to learn about
> > it.
> > One person has suggested to me that it is actually an old style neon
> sign
> > transformer.  It has a winding ratio of 120 to 1 and there is nothing
> > indicating there is a rectifier inside.
> >
> > If this is correct, then I have an old 14.4KV neon sign transformer
> rated
> > for 50KV peak.  The label clearly identifies this transformer as a
> > Potential
> > Transformer.  Perhaps the two are synonymous?  Are there any experts on
> > this
> > list who can clarify this terminology?
> >
> > David Thomson
> > dave-at-volantis-dot-org <mailto:dave-at-volantis-dot-org>
> >
> >
> >
> 
> 
> 
>