Re: HV & ballasts

["Tesla list" <tesla-at-pupman-dot-com>]

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:
			3.33A
		Impedance (loaded): 120/3.33:
			36 ohms.
	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
	So:
		1.25A thru a ballast rated at 1A.

	Repeat for 1KW system and the results get even more
	'interesting'.

	best
	dwp