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Re: Unpowered NST shocks



Hi Gary, all,

Comment interspersed.

> Original Poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
>
> The explanation to the reported shocks from an unplugged NST was
>discussed roughly a year ago on this List.  The suggested
> explanation is that if the NST is switched off while the secondary is
> shorted, the short circuit current circulating in it's secondary would
>persist for a considerable time. Opening the secondary short would
>cause a voltage spike to be developed across the secondary.

True, but as I pointed out in my mail to Alex, the guy who started
this thread shorted the NST AFTER removing power, so this
canīt be the reason ;o)

> However, I also tried a simple experiment on my bench.  I took a 15/30
>NST and hooked a NE-2 bulb across the 2 HV bushings as a HV spike
>ndicator.  I also shorted the two bushings with a separate clip lead.
>I briefly applied, then removed AC power from the primary, and within
>1-2 seconds, removed the short from the secondary.  I repeated this
> several dozen times, but never once saw the bulb flicker.

In the same mail, I pointed out this is EXACTLY my comprehension
problem. No inductor is lossless. By the time you pull the plug and
open the short (takes several seconds at best), the stored energy
will be lost to internal losses (and turned into heat). I DO believe
this will work in a LTR designed coil as the inductor is shorted and
opened many many times per second (depending on the BPS rate)
through the spark gap.

An easy way to replicate the kicker effect w/o harming oneself is
to take a relay (like 24v) and apply power to the coil. While touching
both terminals of the relay coil, remove the power. You will recieve
quite a kick (pun intended), even though the applied voltage is only
24V (the inductive kicking voltage is in the hundreds). It is NOT
dangerous to try this (people with heart problems shouldnīt tho).
And now you know why every DC relay needs a reverse inserted
diode (freewheel)..........


Coiler greets from Germany,
Reinhard