Datasheet
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Fort Lauderdale, FL 33301 USA • 954-766-2800 • www.kemet.com
Single-Ended Aluminum Electrolytic Capacitors – ESK, +85°C
Leakage Current (LC)
Duetothealuminumoxidelayerthatservesasadielectric,asmallcurrentwillcontinuetoflowevenafteraDCvoltagehas
been applied for long periods. This current is called leakage current.
Ahighleakagecurrentflowsafterapplyingvoltagetothecapacitorthendecreasesinafewminutes,forexample,after
prolonged storage without any applied voltage. In the course of continuous operation, the leakage current will decrease and
reach an almost constant value.
After a voltage-free storage the oxide layer may deteriorate, especially at a high temperature. Since there are no leakage
currents to transport oxygen ions to the anode, the oxide layer is not regenerated. The result is that a higher than normal
leakagecurrentwillflowwhenvoltageisappliedafterprolongedstorage.
As the oxide layer is regenerated in use, the leakage current will gradually decrease to its normal level.
The relationship between the leakage current and voltage applied at constant temperature can be shown schematically as
follows:
I
V
R
V
F
V
V
S
Where:
V
F
= Forming voltage
If this level is exceeded, a large quantity of heat and gas will be generated and the capacitor could be damaged.
V
R
= Rated voltage
This level represents the top of the linear part of the curve.
V
S
= Surge voltage
This lies between V
R
and V
F
. The capacitor can be subjected to V
S
for short periods only.
Electrolytic capacitors are subjected to a reforming process before acceptance testing. The purpose of this preconditioning
is to ensure that the same initial conditions are maintained when comparing different products.
Ripple Current (RC)
The maximum ripple current value depends on:
• Ambient temperature
• Surface area of the capacitor (heat dissipation area)
tanδorESR
• Frequency
The capacitor’s life depends on the thermal stress.