overdriven flourescent lights

[Mr. Limpet]

From what I have read, The lamp will draw as much as you give it. Some say that you can blow it up by giving it too much power. The ballast limits this. And putting 2 ballast in parallel does not double the current, due to the design of the ballast. i am still trying to find out more, but I am pretty sure that the bulbs do not have any limiting effect. Paul.

[ronrca]

Lamps blowing up is not true, at least with overdriving them 4x since I have a lamp being overdriven 4x for around a year now. I have not tried using 2 separate ballasts connected in parallel since the increase in power drawn by the lamp does not increase after around 3-3.5x from what I have read. Therefore trying to overdrive them higher than 4x will not achiece anything, just perhaps max the lamp intensity.

[Mr. Limpet]

I don't think you can blow them up using a standard ballast, but if you could drive them harder, they would acccept the power until something gave. My point being that the lamps themselves are not able to limit the power into them. I searched on google for "ballast design", and got a bunch of interesting sites that I am still trying to sort through.
It appears that the longer the lamp, the higher the voltage required to keep it running. At some point the voltage is higher that the 120V input. It appears to be between 36 and 48 inches. At that point the ballast design becomes more complex because you have to step up the voltage. I guess that is why most 8 ft commercial lighting is run at 277 Volts. I always wondered about the 277VAC that you see on commercial panels. Once you have the right voltage, it is just a matter of pumping the right amount of current to get whatever intesity you want.
Now it gets even more complicated, because with new power regulations demanding more efficient lighting, the manufactureres have to go through a lot of tricky designing and you get into such things as Power factors and Crest factors. Also, the move to T8's also includes more efficient reflectors and fixtures. It all gets very complex. I'm still learning here. Paul.