Shelf
life is
specified time for which
a capacitor can be
stored with no applied voltage.
Shelf Life
The
capacitance, ESR and impedance of a capacitor will not change
significantly after extended storage periods, however the leakage
current will very slowly increase.
KEMET
products are particularly stable and allow a shelf life in excess of
three years at 40°C.
The
shelf life of aluminium electrolytic capacitors is limited and
depends from stock conditions.
In
a normal warehouse situation (i.e max 35°C,60% R.H.) the limits as
per Table apply.
Years
|
Limits
|
1
|
Units
will meet initial electrical parameters level
|
2
|
Electrical
parameters check is required to understand if re-ageing is
required
|
3-5
|
Re-ageing
is required before use
|
>
5
|
End
of shelf life
|
Re-age
(Reforming) Procedure
Apply
the rated voltage to the capacitor at room temperature for a period
of one hour, or until the leakage current has fallen to a steady
value below the specified limit. During re-ageing a maximum charging
current of twice the specified leakage current or 5mA (whichever is
greater) is suggested.
Re-Ageing
Procedure
The
re-ageing procedure must be done @ room temperature
and
following steps 1. through 5.:
1.
connect units to a DC power supply through a resistor of :
a.
10k for units having working voltage lower than 100V
b.
100k for units having working voltage lower higher than 100V
2.
increase the voltage checking that the charging current is not
exceding the maximum initial DC leakage limit of the unit
3.
when the rated voltage is reached keep it for at least 4(four) hours
4.
discharge the unit through a 10kW keeping voltage decrease under
control until discharge is complete
5.
test units for DC leakage according to the specification
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