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Re: [APD] Re: incandescent-replacement type fixtures -- or - else!



Thanks, Wright. Of course all this means that my original
comment about capacitors was (to borrow the liguists'
terminology) a tad whacko. I guess no manufacturer that had
lick o' sense would use a cap on the high voltage side. I
won't say which manufacturers that leaves in the running.
;-)

Anyone not impressed by the size of a single Henry (the
basic unit of measurement for induction), then just open up
the largest subwoofer loudspeaker you can find in the house
(go ahead, you only live once) and look for the coil that
keeps all a high notes out of the subwoofer -- you will
know it because it will be the biggest coil you can find in
there. It will be hefty enough to break bones if you drop
it on your toes and it probably measures about 1-5
millihenry (very tiny measures of induction which, I
believe, were named after henry and his wife millie).

Scott H.
--- Wright Huntley <whuntley at verizon_net> wrote:
> Scott's advice is right on.
> 
> Gas discharges are funny things, electrically. One of my
> associates at 
> Stanford University got fascinated by the little NE-2
> neon bulbs we used 
> for panel indicators, in those days. He measured the
> incremental 
> inductance, when one was running, as 1 Henry! That
> normally would take a 
> 500 lb coil of wire and core.
> 
> Switching a current flowing in such a reactance might
> cause far, far 
> higher voltages than Scott even predicted. Bottom line,
> from and old EE, 
> is don't try to switch the flow in wires hooked to the
> tube. It is a 
> *lot* bigger than a little NE-2 and the results are not
> likely to be 
> satisfactory. Switch the incoming power line.
> 
> Wright
> 
> PS. You won't find an ac capacitor that will withstand
> that service, either.
> 
> 
> > Message: 1
> > Date: Wed, 3 Mar 2004 08:33:13 -0800 (PST)
> > From: "S. Hieber" <shieber at yahoo_com>
> > Subject: Re: [APD] Re: incandescent-replacement type
> fixtures -- or -
> > 	living	with an ON/ON switch
> > To: aquatic plants digest <aquatic-plants at actwin_com>
> > 
> > The right value capacitor across the switch terminals
> can
> > prevent momentary arcing that's due to the switch
> contacts
> > almost touching during part of the switching cycle.
> They
> > highrer the voltage the wider the gap the arc can reach
> > across. What value capacitor will prevent the arcing on
> the
> > output, high voltage side, depends on the ballast and
> bulb
> > operating characteristics. Maybe one of the EEs can
> help
> > you there.
> > 
> > But there is another issue. If you're putting the
> switch on
> > the output side of the ballast, the side connected to
> the
> > lamps, then a 125V-rated switch is not adequate and
> > probably not safe. Your ballast and bulb probably run
> with
> > something more like 600 -- 800 volts across the output
> side
> > of the ballast, depending on the bulb and ballast
> > combination. If the ballast is instant start, the
> initial
> > strike voltage is even higher than the running voltage.
> > Much electrical stuff from the hardware store is rated
> for
> > 600V, which isn't really enough either. So first thing
> you
> > need is a switch designed to handle that kind of
> voltage
> > and then some more for a safety margin -- probably
> 1000V.
> > 
> > Whether the Ballasts are remote mounted or not
> shouldn't
> > affect whether the on/off switch arcs *if* the switch
> is on
> > the input side of the ballast.  I'd rather have my
> switches
> > on the input wires and run the wires to where I want a
> > switch than put the swtich on the wires that are
> closest --
> > I'd rather not fiddle with the high voltage if I don't
> have
> > to and I only have to intall the wires once.
> > 
> > Scott H.
> > --- BAshcraft at BrashearLP_com wrote:
> > 
> >>>> > Date: Tue, 2 Mar 2004 13:57:47 -0800 (PST)
> >>
> >>> 
> >>> Could you expand on "dropping a capacitor on the
> switch".
> >>>  My ballasts are 
> >>> remote mounted, but I'd like to be able to turn the
> lamps
> >>> off with 
> >>> switches in the hood.
> >>> 
> >>> I've tried it, and the switch contacts do indeed
> continue
> >>> arcing.  I was 


=====
S. Hieber

-  -   -   -   -   -   -   -
Amano Returns
to the AGA Annual Convention
Nov 2004 -- Baltimore

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