Re: Shocks from NSTs after power down

• To: tesla-at-pupman-dot-com
• Subject: Re: Shocks from NSTs after power down
• From: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Wed, 08 Mar 2000 16:51:29 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi Guys,

I just got back from a break and saw a few posts about getting shocked 
from a Jacobs ladder after the power was turned off.  I had a similar
experience last year,  but fortunately did not actually get bitten !

Malcolm Watts explained this was due to current being sustained
by the massive inductance of the NST secondary.  It would only occur if
the HV leads were shorted during HV arcing,  and Terry worked out that the
circulating current would decay over quite a long time constant.  I had no
problem producing sparks from opening the HV connection,  around 20
seconds or so after cutting the power.  In some cases they were quite
fierce,  in some cases nothing,  depending on where in the AC cycle the
power had been cut.

Terry also did some quite alarming calculations on the possible
amount of stored energy !

This stuff is in the August '99 archives.  The thread was called:

"Danger, and I don't understand why"

Well now I understand why,  but am still very cautious when working with
anything that can store significant amounts of energy.  I would imagine
that pigs and large ballast inductors would be more hazardous in this
respect,  due to their higher L and lower Resistive losses.

Remember safety,  and beware the one thing that you forget to take into
account !

						Cheers,

						-Richie,

• Prev: Re: Salt water caps
• Next: Re: NST insulations
• Index(es):
  • Main
  • Thread