Re: What is Kickback?

To: tesla-at-pupman-dot-com
Subject: Re: What is Kickback?
From: "Megavolt Nick" <tesla-at-fieldfamily.prontoserve.co.uk> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Fri, 07 Jan 2000 21:03:59 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi Gary,
             Kickback takes many forms:

1.Direct strikes to the primary
2.Non-quenching - when the sg does not quench properly the energy from the
secondary is fed back to the primary and primary resonant rise can make this
quite a substantial voltage.
3.Non-firing - when the sq does not fire the pri tank will 'res-up' to a
huge voltage, if it is reso matched.
4.Primary Resonant rise - this is the simple resonant action within the
primary circuit which experiences a Q factor rise (Not a direct Q factor
rise as the seconday mtual inductance is not included in the Q calcs)
5.Parastic Resonance - resonance within the filter networks or other
non-tank components.  This is much more dangerous than Primary Resonant rise
as it is not damped by the high spark gap resistance and mutual inductance
from pri to sec.

These, and many more, modes of 'kickback' introduce large voltage spikes
into the primary circuit which can break down the nst's insulation.
These 'kickbacks' are what the safety gap is designed to prevent. This is
why the safety gap is so important.  I would also advocate a safety gap from
the primary circuit to the rf ground as a better way of dealing with strikes
to the pri. than the normal primary safety gap which under primary strike
conditions can place the transformer under considerable insulation stress.
You may be able to model it with PSpice if you've got that much spare time
on your hands.  Plugging a scope into a real coil is probably easier though.

Regards
Nick Field

----- Original Message -----
From: Tesla List <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, January 06, 2000 7:17 PM
Subject: What is Kickback?


> Original Poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
>
> I see frequent references to "kickback", as something that caps and NST's
> need to be protected against.  Can somebody provide a concise definition
of
> just what this is and its underlying mechanism?  Something that can be
> modeled with PSpice?  I want to understand if there really is such a
thing,
> or is this just a reference to a streamer striking the primary circuit?
> Could it be due to the gap misfiring?  Streamer strikes aside, the only
> thing that I can see going from the secondary to the primary is, after
> quench, the primary and secondary inductors act as an untuned transformer,
> but I think the potential for primary damage is small due to the low
> efficiency of the untuned transformer.
>
> Thanks in advance,
> Gary Lau
> Waltham, MA USA
>
>
>