SAFE Phasing of Neons (fwd)

---------- Forwarded message ----------
Date: Sun, 28 Sep 1997 15:06:50 -0400
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: SAFE Phasing of Neons

> > 
> > ---------- Forwarded message ----------
> > Date: Sat, 27 Sep 1997 13:10:44 +1000
> > From: The Meyer Family <meyer-at-webfront-dot-net.au>
> > To: tesla-at-pupman-dot-com
> > Subject: Power Supplies
> > 
> > Hello,
> >         My name is Andrew Meyer, I am 16 years old and enjoy
experimenting with
> > high voltage devices especially Tesla Coils. I am writing to see
> > anyone can help me. My original coil (6" diameter) has been
powered by one
> > 12kv Neon Sign Xfmr at 30mA. I have recently obtained five more
NST's to
> > hook into the coil. I am writing to ask how you determine the
polarity of
> > the transformer so you can hook up all of the -ves and +ves
> > 
> > Thanks :->
> > 
> > meyer-at-webfront-dot-net.au

The SAFEST method to get two neon sign transformers properly phased
for parallel operation is to connect their cases together and then to
a good AC ground. Then wire the primaries in parallel and attach a
wire with adequate HV insulation to one the first transformer's HV
terminals. Use caution for this next part, as there is the
possibility of having a 12KV potential difference across the gap that
the wire will be forming. I recommend not directly holding the wire,
but rather using an insulated rod to manipulate the hot wire.

When you plug the 120VAC in you can then touch the free end of the
wire to the HV terminals on the second transformer. You will get a
12KV arc to the one that is OUT of phase, and hardly any arc at all
to the HV terminal that is IN phase. If the phasing is the opposite
of that desired, then simply rewire the parallel connection wires
that join the first transformer to the second. In other words, leave
the first transformer alone and just exchange the two primary wires
on the second transformer ONLY.

I know that some people test their transformers by first connecting
one of the HV terminals of the first transformer to one of the HV
terminals of the second transformer. THIS IS VERY DANGEROUS!! If the
HV terminals are wired so that they are AIDING, then the cases of the
two transformers will float to a 12KV difference, and the other two
HV electrodes will rise to a 24 KV difference. This in itself can
lead to transformer destruction, not to mention case to case arcing
and possible case to primary arcing. 

Since neon transformers are center tapped to the case, CONNECT the
cases, and ground the cases to a good AC ground. By the way, the same
goes for when you are actually using the paralleled transformers.
Always connect the cases and ground them to a good AC ground.

Coiling has enough dangers as it is. Let's not take any unnecessary

By the way, if you feel uncomfortable working with the HV output of a
neon transformer, then power the primaries of the transformers with
the output of a 6 or 12 volt transformer. With a 12 volt transformer
the voltage is reduced from 12Kv to 1,200 volts.

Hope this helps.
Fr. Tom McGahee