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Re: HV & ballasts
Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>
Tesla list wrote:
> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> You just gave me an idea!
> I've been thinking about how to build a "variable ballast
>inductor" that has discrete steps. The idea would be inductors
>switched with relays (ss or electromechanical)... I've always
>been stopped by the pain of building the set of inductors.
> What about using fluorescent ballasts just as that... series
>ballast inductors for a polepig type supply...
Well, rough numbers:
40 watt, 4 foot tube, means a ballast to handle
0.4A (roughly). Anyone building 0.4A input coils?
A manyness in Parallel, probably a complex series
parallel mesh. Need to design the switching control
to avoid overloading the inductors. Need to find a
manyness of same value, to keep design simple.
> Especially, if you find some of the big ones used in factories
>for the high output 8 foot tubes
Rule of thumb: 10W per foot of tube. So that's getting
on to 1A per ballast. But. Most such are 'rapid start'
single pit tubes, with internal resonant circuit to
make the spike. I have this Sneaky Suspicion this would
make them Very Complicated (==unstable) to work with.
(and, sometimes, even with two pin lamps, electrically,
the tubes only use open tube and the rapid start
>(which are being replaced....)... We used to have a bunch at my
>former work which were 160W (I can't recall if it was 2 tubes at
>160 each (i.e. 320 W all told) or 2 80W tubes..).
>I think it will be 2x 80W.
> Say they are 320W ballasts...
My recollection ( I think good) is that the
WATTAGE rating is of the ASSEMBLY (lets skip VA
for a bit??), that is ballast plus lamp. Lamps run
40-60VAC, IIR, with the remainder across the ballast.
I Dunno if they run two lamps in series, i think not:
If I'm doing this right in my head, easiest way to
figure it would be to work with the current: 80W
implies a bit under 0.8A at 120V (and some industrial
fluorescents are set up for 240 or 277, so know what's
being got....) ANYway, work with the current is
easiest, i think.
> This means that they have to be able to take a continuous current
>of 3-4 Amps (120V fixtures).
I think otherwise. cf above. 160W for the assembly,
means 2x 0.8A ballasts. Measure one & be sure...
> I think the tubes probably have a voltage drop of 50-60 volts
>after start, so the ballast is dropping some 60 volts
Concur, unless a 240V or 277 (maybe even 480) ballast.
> and must
> therefore have an impedance of around 10-30 ohms...
For the 0.8A case ('80W' tube (Yes. The tube only
actually dissipates about 40W. I believe they are
RATED the other way...)) I think more like 60V/0.8A=
> I imagine that ballasts are available for the carting away...
> When they get marginal in start performance, they just get
> replaced (obviously, you don't want the ones that exploded,
>overheated, failed catastrophically, etc.)...
Certainly possible, but I'd check the numbers a bit.
And i have this image of a manyness in parallel.