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Re: [TCML] NST TESTING.



James,

Are you having trouble with the transformer, or are you just trying "to see what it can do"?

Is it an older iron core transformer, without a built-in GFI circuit, or a newer one, with a GFI?  The newer transformers with the built-in GFI circuits usually need to have the protective circuitry bypassed before they can be used for TC work.  Such transformers usually have a reset button and perhaps a red LED mounted somewhere in the case.  Bypassing the GFI circuits can be a difficult job, especially if the transformer is potted in epoxy instead of the somewhat easier asphalt.

I assume you are not talking about a modern solid state inverter supply, which is not suitable for TC use.

For starters, without the transformer plugged in, I would check the electrical resistance of the primary windings with a DVM (should be a few ohms), and the secondary windings (should be somewhat higher resistance), to be sure that both show electrical continuity.

If you don't have continuity through both the primary and secondary windings, then your transformer is bad, and further testing is futile.

The best way to check the performance under power would be to connect it to a piece of neon sign tube about 4 feet long, if you have one.  You can test it from one secondary terminal to the case, and then it from the other terminal to the case.  NSTs have a center tapped secondary winding with the center tap connected to ground.

If the tube lights each way, then you know that both halves of the secondary are working.

If you do not have a couple of official neon tubes to try it with, then a 4 or 8 foot common fluorescent tube would work as well.  I wouldn't run it for very long, just enough to verify that you are getting high voltage from the transformer.

Make all of your connections before you plug in the transformer, and don't try to change or touch anything while the transformer is energized.

If you don't have any fluorescent tubes to use, then you could make a simple Jacob's Ladder (climbing arc) with a pair of insulators and some stiff coat hanger or heavy copper wire. Again, you can test each output terminal to the case ground terminal, to see if both halves of the transformer secondary are producing an output. Start with a gap of about 1/4" at the bottom of the electrodes.

Dave



On 6/14/2018 6:06 PM, James Janota wrote:
Ok I got a 15kv 30MA 470VA NST. How do I test it safely?

Regards

James Janota

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