Re: lightning arresters

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Nicholas Field by way of Terry Fritz <twftesla-at-qwest-dot-net>" <nick.field-at-hvfx.co.uk>

Hi All,

It is important to note that these arrestors _are not_ continuous duty
devices.  Your pole pig outputting 14.4kV at an amp or so can toast one of
these in a split second.  Do they look like they can dissipate 15kW? ;-)

They are very effective as overvoltage protection in Tesla coil circuits,
however they must be specified to 'fire' at a voltage well above that of the
transformer, to account for resonant rise effects.  You do not want them to
clip every slight transient event, only the big dangerous ones.  Where the
danger threshold comes depends on the robustness and safety margins of your
components

If anyone's interested I have a 15 of these 15kV arrestors manufactured by
the Ohio Brass Company Inc. , unused, in manufacturer's packing, for £10 a
piece plus shipping.  Contact me at nick.field-at-hvfx.co.uk for details.

Safe Coiling,
Nick
_______________
Nick Field, HVFX
www.hvfx.co.uk

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, October 22, 2002 7:54 PM
Subject: RE: lightning arresters


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<tesla729-at-cs-dot-com>
>
> "Tesla list" <tesla-at-pupman-dot-com> wrote:
>
> >Original poster: "Godfrey Loudner by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <ggreen-at-gwtc-dot-net>
> >
> >I have some lightning arresters for from the local junkyard and have no
idea
> >as to their reliability. If one of the arresters is
> >placed across an x-ray transformer with a short spark gap in series,
> >bringing up the voltage with a variac causes little
> >blue sparks across the gap. As the voltage is increased, the intensity of
> >the blue sparks increases until a flame appears.
> >In the past, I mistakenly thought the appearance of the flame was a
sudden
> >switching on of the arrester. But actually the current becomes high
enough
> >to support a flame. The appearance of the flame is gradual, not sudden.
Is
> >this how
> >arresters are suppose to behave? I thought that the arrester would
suddenly
> >switch on. Quite possibly the arresters
> >are bad. There are a couple of guys on the list who wanted one for their
> >14,400 volt pole pigs, but the is no use shipping such heavy objects for
> >only shipping charges if they are bad.
> >
> >Godfrey Loudner
> >
> >
> >
> >
> >
> Hi Godfrey,
>
> I had talked to you about getting an arrester for my pig, but I just
> recently aquired three 15 kV rated ones off of ebay. The 15 kV ones
> seem to be about right as they don't start shunting out my pig's
> output to the coil at only about 70% variac setting like the 12 kV
> rated one did.
>
> Regarding your query about the reliability of the ones that you
> retrieved from a junk yard: I think what you described is "normal"
> operation for a lightning arrester, as I'm noticed this same
> phenomenon in my 12 kV rated arrester and it definitely "worked"
> in my coil system (the 12 kV rating made it cut off too fast with
> my 14.4 kV pig).
>
> Sparkin' in Memphis,
> David Rieben
>
>
>