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Don Klipstein

In ,
wrote:

Bob M. wrote:
"CJT" wrote:
... and bulbs last (almost) forever with electronic ballasts.

This I've not heard before. Why do they last longer? It seems the filaments
are still being subjected to the stresses of current inrush when turned on.

The cheap electronic T8 ballasts I've been using have one wire that goes
to both filaments pins at the end of a tube, so current never flows from
one pin to the other through the filament.

This is an "instant start" ballast. The usual alternative is "rapid
start", where the filaments are heated during starting and during use.

T8 lamps are generally rated to be suitable for both rapid start and
instant start. Sometimes they had different life expectancy figures for
the two different starting methods, and when there was this difference the
life expectancy is shorter with instant start. Starting causes more wear
on the filaments when the filaments are not heated by current flowing
through them.

Keep in mind that in my experience about 99% of failed fluorescent lamps
failed from depletion of emissive material on the filaments, as opposed to
breakage of the filaments or the bulb.

Most fluorescent lamp filament breakage leading to lamp failure in my
experience is caused by extremely severe power surges that cause mass
burnouts. So far in my life, I have twice seen fluorescent lamps affected
by this phenomenon, both times in the same location. I have heard of this
before and it appears to be uncommon.

- Don Klipstein )