I have built a dozen or so UV lights over the past ten years. I always copied regular commercial lamps when I selected ballasts and other components, matching lamp wattage and ballast ratting. Over the years I have heard a lot of discussion on "overdriving" UV lamps to increase their power output. At least two manufacturers have comments in their literature that the lamps (tubes or bulbs) on their lights are overdriven. This has lead me to a bit o' confusion, and a number of questions about overdriving lamps and ballast selection in general. Possibly someone who actually understands the subject could enlighten me.
As I understand it, overdriving a lamp involves simply using a ballast designed for a higher wattage lamp. In exchange for this greater power output there is some sacrifice in the life of the lamp. So, my questions are;
By how much does going to a more powerful ballast increase lamp output? I have put 15 watt MW tubes into a lamp with 25 watt ballasts. I see only a minor change in output over the same lamp run with a 15 watt ballast. I have never actually measured the difference.
Does overdriving a lamp really cause a significant loss in lamp life. Does it reduce the number of on-off cycles that the lamp can handle?
Is there a practical limit on how much a lamp can be overdriven by? What happens if I drive an 18 inch tube with the ballast for say an 8 foot lamp ?
Is there a difference in output driving a lamp with a newer solid state ballast over an old style magnetic ballast?
I recently overheard a comment that leads me to think that different size and type lamps, U or H shape lamps or straight tubes, run at different voltages. Not the 110v or 120v that the ballast draws, but the ballast output voltage. Is this true, and does it factor into selecting a ballast to overdrive a lamp? Assuming that one owns a VOM, how do you measure this?
Is there a significant difference between ballast manufacturers, or is price the main deciding factor in selecting a ballast?
Since I am about to reballast a couple lamps to eliminate an annoying hum any assistance would be appreciated.