On 2008-09-04, Don Bruder <dakidd@[EMAIL PROTECTED]
> wrote:
> In article <LLydnV7NW6y3UyLVnZ2dnUVZ_orinZ2d@[EMAIL PROTECTED]
>,
> "Dave" <db5151@[EMAIL PROTECTED]
> wrote:
>
>> "Eeyore" <rabbitsfriendsandrelations@[EMAIL PROTECTED]
> wrote in message
>> news:48BFC5D3.566F1BA9@[EMAIL PROTECTED]
>> >
>> >
>> > Dave wrote:
>> >
>> >> It seems to me that a flourescent ballast is probably just a
transformer
>> >> and
>> >> a high-voltage electrolytic cap. And when it "goes out" it's
probably
>> >> because the cap failed. If these are true, could I just replace the
cap
>> >> and
>> >> make it work again?
>
> In all of the flourescent fixtures I've seen that use a cap, it was just
> a small ceramic disk capacitor wired across a little NE-4 or similar
> bulb, both contained in the easily replaced "starter" can. (But those
> were *OLD* fixtures - At least 20 years old) No caps to be seen anywhere
> else in them.
the power factor correction caps are optional in some settings
(eg domestic use) and required in others (eg commercial use),
wether or not the cap is needed is a matter for the makers of the
electricity regulations.
When you get 100 or more florescent fixtures all running at once
(like you could in a school or supermarket) the large load with
a power factor would be pretty horrible, the caps clean it up a bit.
I remeber the electricians discarding pitch-filled capacitors what had
partially de-potted themselves while they were doing maintenance on the
flourescent fixtures at high school.
> Last year, we had the ballast in an 8 foot fixture die, and it came
> scary-close to burning down the barn
8-foot? is that two 4 foot tubes? or do they make 8 foot tubes?
the longest I've seen are 5 foot tubes.
hmm, I should dig out inverter I made and make me a light sabre :)
that bulb in the starter is not a simple neon either, there's a
bi-metallic strip in there that un-shorts it when it warms up,
while the starter is shorted the power flows through the filaments in
the tube and warms up the electrodes.
Bye.
Jasen
|
