hv transformer wiring

[evengravy]

hi,

I am building an ozone generator using a high voltage neon sign transformer and I am a little unsure of wiring. The transformer I have is brand new and runs off 230v and produces 3kv@9ma. I want to be 100% sure of how to wire this safely for obvious reason so I would appreciate your assistance guys/gals.

Basically the nst that I have bought is like in the image attached.

The ozone generator electrodes will consist of a scroll of stainless steel mesh that is pushed into a Pyrex test-tube where it unfurls against the walls and a lug on the end makes connection to the circuit through a nut and bolt through the screw-on lid. A stainless steel mesh tube on the outside of the test-tube acts as the other mesh electrode and is connected to ground via the terry clip mountings that hold the assembly in place. 

The secondary side of my transformer is not marked, do I simply ground one side of the secondary (which will be the outer electrode) and tie this to the case also?

View attachment 41253

View attachment 41254

View attachment 41255

 

[evengravy]

My current thinking is to wire the secondary to the electrode like the image attached,

Since one side of the secondary is contained within a sealed pyrex tube I am presuming this is correct but I would appreciate input/corrections, thanks.

View attachment 41256

 

[Hero999]

That looks fine to me.

he red wires are the secondary and the brown and blue are the primary.

 

[evengravy]

thanks hero,

one question, does it matter which wire of the secondary is grounded? there are no markings on the secondary wires at all, and they are both the same colour.

am I correct in thinking one secondary wire is + and one - that should be grounded? if so how would I identify which is +?

my thinking is that the turns ratio is 1:13 so if I apply mains voltage to the secondary side and measure the primary side as it produces a safer measurable voltage this way,  I can determine the + and - wires on the secondary.

Not sure if this is even necessary?

Thanks, even

 

[Hero999]

How can one wire be + and the other - when it's AC?

The winding doesn't need to be grounded.

You're right, the ratio will be 1:13 because it's the ratio of primary to secondary voltage, there's no need to measure it.

Although you'lll probably fry the meter trying to measure 3kV, the transformer is unlikely to deliver a lethal shock because the current will be limited by the high leakage inductance. I know this because the secondary winding is grossly oversized which increases its inductance and limits the current and that a neon lamp is an arc lamp which needs a current limited power supply.

 

[evengravy]

Thanks hero,
I've been working with hv dc ozone up until now so sorry for the confusion,

just so I'm clear could you check my wiring diagram?

Thanks, even

View attachment 41257

 

[Hero999]

That will work fine.

 

[evengravy]

hero,

thanks very much, even

 

[Stephenah]

thank you.I would like to read this.

 

[awright1]

While it is true that a neon sign transformer is current limited by design, do NOT assume that you can be casual about dealing with the high voltage.  It only takes 10-20 ma through the heart to throw it into fibrulation with possibly lethal results and I believe that neon signs operate on higher currents than this.  I presume you do not have a spec sheet on your transformer telling you what the current limit is.  In any case, the nominal current for fibrulation is an average.  You or your guests may be more sensitive. 

Be sure there is no possibility of human contact with the hot secondary lead and that the other end of the secondary is solidly grounded.

I urge you to read this Wikipedia entry on NSTs before proceeding.
http://en.wikipedia.org/wiki/Neon_sign_transformer

awright