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Re: series neon xformer dc power supply?


    I was looking for a true neon transformer spec sheet when I had found a
http://www.worldyellowpages-dot-com/hupchung/  Sign Transformer.  I remember
something from the Movie DUNE.

    In this catalog on page A-19 listed at the bottom of the page is a
series of coil, and core transformers.
http://www.allanson-dot-com/products/transformer.pdf

    Now, for safety sake, I am showing you by how much the primary has to be
isolated from the secondary for the parallel primarys, with the series
secondarys based upon both the primarys, and secondarys being in phase.  If
I had two of those transformers with exactly the same specs, and model
number.  The two primary could be placed in parallel as long as they are in
phase.  Assuming that these transformers were wound exactly the same by a
company standard, I should be able to reliably take the top primary wire of
the both transformers when they both lay the same way on a table as in the
picture.  Then both of the bottom wires, and join them.  The top pair of
wires would go directly to the switch for the main 120VAC, the second pair
directly to the prong of the outlet through the cord.  According to the top
of the list on the spec sheet for that type of transformer one will draw
1.35 Amperes, and two will draw 2.7 Amperes in parallel.

    At this point I have the secondarys to be concerned with.  For the phase
relationship to be right, that would be the top wire of one on the table
with both transformers facing me on the table exactly as in the picture, and
the bottom wire of the other, and joining those two wires places the outputs
in series.  Now, when I measure the voltage from the unconnected wires left
from one transformer to the other, I will have 15 Kv at 20 mA.

    The right to ground this, is find which of the two prong wires are hot
in respect to the third grounding prong.  Your house current is designed
from a split to ground from ground 220 VAC, or 240 VAC 60 Hz system in
America.  So, the wall transformer really gives you one side of the main
transformer, and Earth Ground as 110 VAC, or 120 VAC because, the center tap
is Earth Ground.  So, one of the two prongs will have 0 volts if the house
is wired correctly, and the other will have 110 VAC, or 120 VAC to the third
Prong or the ground prong.  This means that one side of the system is earth
ground, and the third prong is actually a high current handling Earth Ground
which bypasses the circuit breakers.  This helps to prevent people from
getting shocked, and doesn't protect equipment so well.  It is that way to
protect you.  Break out your DMM, or VOM, and go check the wall outlet.
Some houses are not wired correctly, and they are typically over 50 years
old.  Most have been upgraded to present standards but, you have got to
check first.

    Now, back to the parallel input, series output transformer
configuration.  What you need to do to save your transformers Isolation, and
insulation is find which of the two are actually earth ground then join that
prong wire to the third prong wire, and only the pair of wires that are
joined on the output which place the secondarys in series.  The insulation
cannot recognize the difference beyond its normal output it's just plus, or
minus half of the output voltage of the two in series in respect to ground,
or they are responding in the same fashion, and only step up the voltage the
same amount above the ground.  This is true with a metal chassis that is
earth grounded, it cannot tell the difference from the core.  Second, it is
an inductive voltage divider, and impedance will always place half of the
voltage of the two transformers on one side of ground, or the full output of
one transformer on one transformer.  They cannot feel the difference in
watts the current hasn't change per transformer and is still at 20 mA.  Even
when you marry the circuit to the two unconnected wires the load is
distributed by inductive reactance.  It just works like that doubling, there
would be a difference that would effect the insulation if you used a third
transformer that would be felt on the primary as a result of the doubling of
the series circuit made of the secondarys, because you can only afford one
ground and as soon as you placed a third transformer into the parallel
input, series aiding output arrangement then you will have double the
voltage felt on the primarys of two transformers above ground.

James.



>Original Poster: "John" <jbowers1-at-jnlk-dot-com>
>
>Hello all,
>
>I recently came across a website with a schematic for a dc power supply
>using two 15 Kv neons in series feeding a full wave high voltage dc
>rectifier (both diode and tube rectifiers are presented).  The author notes
>that after rectification, the supply is capable of around 42 Kv output (30
>Kv before).  Now I've read a lot of material suggesting that neons cannot
>be used in series, only parallel, and I'm wondering if such a supply would
>work without harming the neons?
>
>Thanks,
>John Bowers
>
>