David.Obdrzalek na mff.cuni.cz
Pondělí Březen 7 17:04:49 CET 2011
Narazil jsem na zpravicku v Q/A u Farnellu, prodavam jak jsem koupil:
Q: I notice that a lot of aluminium electrolytic has stated life times that can be
as low as 2000 hours. Does this mean that a product that is in use for 40 hours a
week would only last a year?
A: This is true but this figure is at the max working voltage and at the max
ambient temperature of the capacitor. Fortunately, by reducing the working voltage
and/or the ambient temperature of the capacitor, the life of the capacitor
increases dramatically. The bigges factor of the two is the ambient temperature.
The following equation shows that where voltage has a proportional effect,
temperature has an exponential effect:
Lfinal = Lr * ( Vr / Vw ) * 2^Th
where Th = (Tr - Ta + Dt) / 10
Lr = Rated life of the capacitor
Vr = Rated voltage of the capacitor
Vw = Working voltage of the capacitor
Tr = Rated temperature of the capacitor
Ta = Ambient temperature
Dt = Temperature increase due to the ripple current which is the hard part to
establish but can be measured.
Taking an example of a 63V, 105°C capacitor with a life of 2000 hours, we can
extend the life to over 142,000 hours if we have a working voltage of 40V and a
temperature of 50°C, a 70 fold increase.
Zdroj ovsem nerika, jak k tomu vzorecku prisel. Je mozne, ze by to bylo az tak
jednoduche (a silne)?
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