Re: NST current, was Filters & Chokes

[FutureT-at-xxxxxxx (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

In a message dated 11/14/00 9:45:51 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

> Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com> 
>  
>  I use a standard unmodified 15/60 NST and the filter uses a pair of 1.6K
>  113W resistors.  For a very long time I was puzzled at just how hot these
>  got.  By standard logic, the power is I^2 R, or .06^2 * 1600 = 5.76Watts.
>  But after building a fiber-optic VI probe, I was able to scope the NST
>  secondary current with a digital scope, which also performs true-RMS
>  calculations.  Guess what?  My 60mA NST is pushing 184 mA, RMS.  It appears
>  that some unexpected things happen when charging an LTR cap, speculation is
>  that the current shunts saturate and allow far more current to pass.  So 
the
>  184 mA causes a dissipation of 54 Watts per resistor.
>  
>  Gary Lau

Gary, all,

I use a 12/30 NST with LTR cap, and it pushes about 50ma, but this
only happens if I turn up the voltage to 140volts input using a step
up type variac.  I seem to remember that you're using a step up
variac also?  With a normal 120 volts input, my NST just gives the
rated 30ma to the coil.  But if I use a matched size cap, then I can 
get 50ma with just 120 volts input.  I haven't tried 140 volts into a
shorted output NST to see what the current is.  The 140 volts input
probably has a lot to do with increasing the current.

John Freau