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Nst transformer? Answered

How do I find out how much current my transformer can drive? How do I compare the drive of my transformer, and what's the purpose?


The drive current of a transformer is usually limited the size of the wire on the secondary windings. Small diameter wire, small current. In the case of a neon sign supply, the voltages are high, but the current is low. (You won't be welding very much with it)

Wiki says this:

They convert line voltage from the 120-347 V range up to high voltages, usually in the range of 2 to 15 kV. Most of these transformers generate between 30 - 120 mA.




4 years ago

Here is what I use.


...but that won't measure the output POWER capability, will it ? You're driving an open circuit ( and pray your meter can handle several kV directly.....)

True, but  power is not my first concern.
  • I usually need to find out if the primary is a mains voltage able winding.
  • See picture of what I mean.
  • Then I want to know the secondary output voltage
  • Finally Power comes up and how much current can it deliver.
  1. My first inkling of the power ability is the size and weight ( Heft )
  2. Then the construction ie coils, or bobbin material.
  3. Then the visible insulation gives me an idea of operable temperature.
  4. Is it an old Radio Shack slap together metal encased fire starter.
  6. Ultimately a fully loaded thermal run will determine the POWER

But our author was asking about an NST ( Neon Sign Transformer )
and today that could be a resonant instant start transformer with air-gap
current limiting final output ( hard to use on anything else then mercury vapor )


If you know the open circuit volts, you can determine the output resistance of the source. The maximum amount of power you should be pulling should be that into the same resistance.
So, OC volts = 1000V,
SC amps =0.03
resistance = 1000/0.03 = 33KOhm.

Load = 33kOhm, output power = 5002
=7.5W. Put your own,. accurate, numbers in

What will 30ma(short circuit) do for me?