Re: [APD] Reactive Ballast

["S. Hieber" <shieber at yahoo_com>]

Sounds like a simple coil ballast? Not liek a stepdown since there is only a single winding. The bulb is started by routing current through the bulb filaments in series and the coil for a moment (usually a small starter, a momentary, normally open switch, is used). When the starter switch closes it heats the bulb, vaporizing the mercury in the tube and putting an magnetic field aroudnthe coil. When the switch opens up, which happens almost immediately when current is running through it, the collapse of the magnetic field on the coil causes a brief voltage surge which gets the bulb arcing across the tube. The AC current through the coil keeps the voltage up for operation after that. The coil also presents an impedance to the AC, which limits the amount of current that the bulb can draw -- hence the term "ballast". Without that impedance, a fluourscent bulb would draw more and more current until it had an active failure (i.e., pow!).

Some of the small bulbs, like many 7, 9, 11, and 13-watt u-tubes, have the starter built into the base of the bulb. For these bulbs you would want to stick with a magnetic ballast. Some of the small u-tubes don't have the starter built in but those are kind of hard to find.
 
sh
 
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----- Original Message ----
From: Chris Hotte <ecwh73 at gmail_com>
To: aquatic plants digest <aquatic-plants at actwin_com>
Sent: Tuesday, September 11, 2007 10:03:39 PM
Subject: Re: [APD] Reactive Ballast


S. Hieber wrote:
> It depends on the starting requirments of the intended bulbs and the ballast, not just the general operating requirements.
I was reading a bit into that. There are no capacitors in line with the 
circuit. I cracked open the ballast casing which is like a standard 
stepdown AC/DC transformer bulky plug type. It appears like a 
transformer with a surrounding square of metal, which is not a permanent 
magnet, as it has no effect on my CRT. Since it's a 13W bulb, I'm to 
understand that the initial spark is possible from the standard 120V 
before the reactance kicks in.

Seen here: http://ecwh.yi.org/CFL%20001.jpg

I suppose I could cart it off to a local electrical supply shop for 
identification.

- C
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