Re: Filters for non - NST primary

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Gary, Phil,

Yes, pigs are "darn-near" bullet proof as a Tesla coil
power supply but I still like the idea of at least SOME
type of overvoltage protection. Electrical utilities use
what's know as a "distribution arrester" in parallel with
the HV primary line voltage input to the pig to protect
it from line surges caused by lightning strikes or swithing
surges. Internally, they are basically a BIG MOV and
are designed to start "clipping" the line voltage when it
substantially (>20%?) exceeds the rated voltage of the pig.
That's what I use with mine and you can check it out at:
http://dawntreader.net/hvgroup/david/gm.html It's on the very first 
picture. It's rated at 18 kV and it
hasn't clipped any with my 14.4 kV pig, even when over-
driven with 280 volts in for 16.8 kV out. I know it does
work though because I checked it out by carefully ramping
up a voltage across it with an x-ray transformer. It seemed
like it started clipping around 25 kV or so which is WELL
within the safety range for the HV side of a 14.4 kV pig as
I think a typical 14.4 kV pig's HV winding side is rated for 110 kV 
BIL. Distribution arresters occasionally show up on ebay or you might 
could contact your local power company
about one.

David Rieben

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, October 13, 2005 9:55 PM
Subject: RE: Filters for non - NST primary


> Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
> Charging current is far higher from a pig and would probably fry the
> resistors.  Also, should the cap selection or other variables cause the
> charging voltage to go too high, the MOV's would quickly fry.
> As far as pigs on the web using chokes, all I can say is don't believe
> everything you read on the web.  Pigs are bulletproof compared to NST's
> and need no external protection, but you can add chokes if you think
> they look nice.
> Regards, Gary Lau
> MA, USA
>
> > Original poster: FIFTYGUY@xxxxxxx
> >
> > In a message dated 10/13/05 10:17:51 AM Eastern Daylight Time,
> > tesla@xxxxxxxxxx writes:
> >
> >  > The Terry filter is only for NSTs.
> >
> >      How come? Why would it be unsuitable for a pig, MOT, PT, etc.? I
> > don't see how it could hurt.
> >      IIRC the pig setups I've seen on the Web *do* use the filtering
> > chokes on the secondary lines. I understand weird resonances and
> > other problems can occur with shunted transformers, such as NSTs,
> > when using filter chokes. Has anybody determined if they are of
> > harm/benefit on the larger systems?
> >
> > -Phil LaBudde
> >