[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: HV & ballasts
Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>
>>Rule of thumb: 10W per foot of tube. So that's getting
>>on to 1A per ballast.
For a particular tube, say 100 W.
>>But. Most such are 'rapid start' single pin tubes, with
>>internal resonant circuit to make the starting 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 startballast.)
'rapid start' was poorly chosen on my part. I ferget
what the buzzword is the filamentless tubes. I'd
still be nervous of those ballasts, as above.
>>>(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..).
> Actually, they were 120W tubes (having just called the shop
>manager and asked...)
> Also, I find (on one of the zillions of web sites that talk about how
> wonderful brand X ballasts are) that "rapid start" means that they apply
> power to the filaments and HV to the tube simultaneously.
cf above, my bad.
> There is a capacitor on some ballasts, across the power line,
>to do PFC. Easily distinguished, because the ballast will
>either say (in tiny print) something like PF=0.75, or, in
>great big type "New Improved Power Factor PF=.98".
> And, yes, a bunch in parallel...
> Say you had 15 of them... I'd wire them up in a 1,2,4,8,
>kind of pattern, giving you (in this case), 16 power steps
>(actually 17.. no ballast)
My concern is the cases were few ballasts are in series
with the Tesla System power transformer:
If the input current to THAT is large, one
could exceed the current rating of the ballast.
Picking some numbers from the air:
400W Tesla System transformer, 120 V:
Impedance (loaded): 120/3.33:
Taking a single fluorescent Ballast, '100w' nominal:
1A (roughly) with 50v (roughly) across the, tube
60V/1A = 60 ohms impedance.
(Some may argue that the '100w' tube is only getting ca
50W. That's The Way Fluorescent ratings are done...)
System impedance (loaded): 96 ohms
System current: 120/96 == 1.25A
1.25A thru a ballast rated at 1A.
Repeat for 1KW system and the results get even more