21

© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com

A4018_ELH • 2/10/2016

Snap-In Aluminum Electrolytic Capacitors – ELH Series, +85ºC

Leakage Current (LC) cont’d

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:

Where:

V

If this level is exceeded, a large quantity of heat and gas will be

generated and the capacitor could be damaged.

V

This level represents the top of the linear part of the curve.

V

This lies between V

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)

tan δ or ESR

• Frequency

The capacitor’s life depends on the thermal stress.

Frequency Dependence of the Ripple Current

ESR and, thus, the tan δ depend on the frequency of the applied voltage. This indicates that the allowed ripple current is also a function

of the frequency.

Temperature Dependence of the Ripple Current

The data sheet specifies maximum ripple current at the upper category temperature for each capacitor.

Expected Life Calculation

Expected life depends on operating temperature according to

Where:

L:

Expected life

Lo:

Load life at maximum permissible operating

temperature

T:

Actual operating temperature

To:

Maximum permissible operating temperature

This formula is applicable between 40°C and To.

I

V

R

V

F

V

V

S

Expected Life Calculation Chart

Expected life (h)