It's a very fine relationship between efficiency and life. Drop the
efficiency and the life goes up dramatically. Think of, say, panel
illumination lights on a car versus headlamps - the headlamps are likely
to fail three or more times as often.
*Pride is what we have. Vanity is what others have.
Dave Plowman email@example.com London SW
The formula quoted in the wiki (don't know its source) is:
new life / old life = ( old voltage / new voltage ) ^1^3
(that raised to the thriteenth power in case it does not look ring in ASCII)
so 1000 hours at 230 volt would become:
nl / 1000 = (230/240)^1^3 = 0.58
so life = 1000 x 0.58 or 580 hours at 240V.
If you modify that to...
Falls very steeply at the start, stays at a fairly constant low level
and then gradually rises - I would agree, but it's that initial plummet
& the gradual rise at the end that is characteristic.
Sharp fall at the front sure... the end rise will vary depending on the
typical causes of failure. Some designs hit a wall at end of life due to
particular component limitations etc, so it can be as steep there aswell.
when clearly that cant be the failure mode?
I'd look at oxidation at or around the operating temperature. I bet
that's a sharp knee.
Or whether in fact the material strength starts to undergo a transition
at that temperature
To get light efficiency you run filaments as hot as they can go.
(in-ep-toc’-ra-cy) – a system of government where the least capable to lead
Others have already mentioned voltage, and vibration. Lamp brand also
has an effect. I found a batch bought from TLC outperformed some others
that I had tried previously for example.
There have been various discussions on this in the past (a particularly
good one some years back that got hijacked by one of our US based trolls).
One thing that a number seem to agree on (myself included) is that mains
voltage halogens are also intolerant of noisy switching, So it is
worthwhile swapping the switch for a new one as a precaution. (or better
still using a soft start dimmer to drive them)
For a real fix however, swap them for LV halogen or LED
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