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Re: NST question

Hi David,

        Your NST, will put out 15kV at zero amps into an open load or 0
volts at
60 mA into a short.  The most power one "should" be able to pull out of it
would be when the NST is putting out 7.5kV at 30mA (250000 ohms) or 225 watts
when the source "resistance" is matched to the load resistance.

        In a neon signs (another use for a NSTs ;-)) the transformer is almost
always running into a "near" short.  If a 15kv/60 NST is shorted it will draw
7.5 amps from the AC line (due to the voltage and current transformation
ratio).  7.5 amps at 120 volts is 900VA (volt amps).  They don't say watts
because the voltage and current waveforms are way out of phase so the "real
power" (watts) is far less.  I imagine Jefferson has measured the "real" power
running into neon signs and they decided to rate their transformer that way.  I
have seen a fairly wide number of ratings on 15/60 transformers and it really
just depends on what the manufacturer feels like putting on it.  My Transco
says 900VA at 8.25 amps...

Of course, when we get them hooked to a coil, we can play all kinds of tricks
to get 900 (and more!) real watts out of them mostly by sizing the primary cap
to cancel the transformer's current limiting.

So, if it says 15000 volts max at 60 mA max, you have the right transformer
regardless of the other babblings on the label.  ;-))

Cheers,

        Terry


At 02:52 PM 03/17/2000 -0500, you wrote: 
>
>     I have a Jefferson Electric 15 KV NST rated at 60 milliamps (1 out of a
> dozen free!), BUT the the tag also says that it only uses 500 watts. 
> Shouldn't it be closer to 900 watts? why is the tag contradicting itsself?
> Should I still consider it to be 60 milliamps?
>      ~Dave