Re: RC filter resistor

["acmnovak" <acmnovak-at-xxxxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Maybe a string of 3 60 watt or 6 30 watt bulbs would suffice?
The voltage differential between them would be like a few KV each which
would certainly not be a problem...
Later-
-Mike


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, November 05, 2000 4:57 PM
Subject: Re: RC filter resistor


> Original poster: "David W" <Dav_W926-at-hotmail-dot-com>
>
> You are all talking about 50 ohms, 100ohms, etc. But I thought that a
filter
> resister for a TC system needed to be about a couple kilo ohms.  That's a
> lot more than a light bulb.
>
>
>
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Sunday, November 05, 2000 2:47 PM
> Subject: Re: RC filter resistor
>
>
> > Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
> >
> > A 100W light bulb, when hot, is roughly a 100 ohm resistor.  Sure, it
> would
> > work, but here are the practical problems:
> > 1) The resistance varies a LOT from cold to hot. Very low when cold
> > relative to the hot temperature. Standard 300W halogen bulb (nominally
> > around 48 ohms when hot is about 3.5 ohms when cold.
> >
> > 2) Breakdown voltage. A standard 100W bulb and socket isn't going to
hold
> > off the high voltage real well because the clearances are kind of close
> > (look how close the wires are inside the bulb.  In theory, the resistor
> > potentially needs to take the full supply voltage at some point in the
> > cycle.
> >
> > That said, something like a 150W halogen bulb or 300W halogen bulb might
> > not be a bad idea.  They are long enough that breakdown voltage isn't an
> > issue, and if you size it for the cold resistance, then you might have a
> > winner. If you have a 30 mA NST, the bulb's not even going to get warm
> > (considering normal operating current is around 2.5A for a 300W bulb).
> > OTOH, there might be easier ways to get a 3 ohm resistor (like a fairly
> > short length of nichrome wire).
> >
> > Scavenging an old toaster or electric heater might be a way to get
> nichrome
> > cheap, if you don't just buy it.
> >
> >
> >
> > ----------
> > > From: Tesla list <tesla-at-pupman-dot-com>
> > > To: tesla-at-pupman-dot-com
> > > Subject: RC filter resistor
> > > Date: Sunday, November 05, 2000 8:26 AM
> > >
> > > Original poster: "acmnovak" <acmnovak-at-email.msn-dot-com>
> > >
> > > Could a light bulb (>100 watts) be used as a power resistor in a RC
> > filter?
> > > They are made for heat and are redily avaiable most everywhere...
> > > The fact that power resistors heat up and are not easy to find in the
> > right
> > > values really kinda makes me wanna avoid the whole RC filter
situation.
> > A
> > > filter composed of two 100 watt lightbulbs, a safety gap, and a bypass
> > cap
> > > would be a cheap and easy way for one to protect a hard to
> find/expensive
> > > xformer..
> > > Thanks
> > >     -Michael
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
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