Lifetime Estimation

Life Time Estimation
Lifetime Estimation of Aluminum Electrolytic Capacitors from Jianghai
To estimate the Lifetime of a non-solid Aluminum Electrolytic Capacitor from Jianghai, the following formulas can be utilized. The
Lifetime depends mainly on the ambient temperature, the ripple current and, within certain limits, the operating voltage applied.
Other parameters may also affect the Lifetime. Moreover, L0 can be interpreted in many different ways, which has a fundamental
influence on the numerical result. Jianghai offers a high transparency by publishing the different typical definitions of Lifetimes in
each datasheet. Lifetime estimations are approximations by nature.
Please let JIANGHAI EUROPE confirm any result before using it. The formulas given here do not constitute part of a contract nor
of a specification. The formulas do not cover additional aging effects of certain electrolytic systems or other chemical effects. Please
contact us should you need Lifetime estimates for Solid Electrolyte Polymer Capacitors. Also the dimensions of the components
may have an effect. Forced cooling or other additional cooling-methods have a strong impact on the Lifetime and are not covered
by the formulas.
For the estimation and interpretation of Lifetime, a close collaboration with JIANGHAI EUROPE is strongly advised.
Structural formula:
Where:
1.
L = L0 · KT · KR · KV
L Total Lifetime
L0 Lifetime under Rated Ripple Current at Upper
Category Temperature (see catalogue)
KT Temperature Factor
KR Ripple Current Factor
KV Voltage Factor
KT Temperature Factor:
Aluminum Electrolytic Capacitors follow roughly the 10 K rule of Arrhenius. It is possible to estimate the Lifetime by
rule of thumb: When the operational temperature is reduced by 10 K, the Lifetime will double. The formula for KT in detail is:
T0 - TA
KT = 2
Where:
2.
T0
TA
10K
Upper Category Temperature
Ambient Temperature
KR Ripple Current Factor:
The influence of ripple current on Lifetime can be estimated according to the following formula:
KR = Ki
v2014.1
14
A
∆ T0
10K
( )
IA
2
With:
A= 1–
Where:
IA Actual Rated Ripple Current
IR Ripple Current at Upper Category Temperature (databook value)
ΔT0 Core Temperature Rise of the capacitor
(typically 5K for T0 = 105°C and 10K for T0 = 85°C)
Ki Basis, defined as
T0 = 105°C IA > IR: Ki = 4
IA ≤ IR: Ki = 2
T0 = 85°C Ki = 2
IR
Assistance needed? Please contact Jianghai Europe GmbH +49 (0) 2151 652088-72 or [email protected]
Life Time Estimation
3.
KV Voltage Factor:
For Radial Electrolytic Capacitors, this part of the formula has no impact (KV = 1). But for some bigger capacitors like Snap-In and
Screw-Terminal types with rated voltages above 350V, the operating voltage will affect their Lifetime. It is expressed as follows:
Where:
KV =
( )
UR
UA
n
Rated Voltage
Actual Operating Voltage
Exponent, defined as:
UA
UR
UA
0,5 ≤
4.
UA
→ n = 2,5
< 0,5 → n = 0
UR
Frequency Correction Factors:
If the actual Ripple Currents are not given at the same frequency like I0, weighing factors need to be applied.
If 1
( )
IA =
2
Ff 1
IA
If1 ... Ifn
Ff1 ...Ffn
5.
≤1
UR
0<
-n
+
If 2
( )
2
Ff 2
+ ...
If n
( )
2
Ff n
Actual Rated Ripple Current (normalized)
Ripple Currents at different frequencies
Frequency Correction Factors for different frequencies
JIANGHAI Electrolytic Capacitor Lifetime Estimation Formula
L = L0 · KT · KR · KV
T0-TA
=
L0· 2
T0 = 105°C
T0 =
0,5 ≤
0<
85°C
UA
UR
UA
UR
10K
· Ki
IA > IR →
IA ≤ IR →
→
≤ 1
[1- (
Ki
Ki
Ki
=
=
=
IA
IR
)
2
]·
∆ T0
10K
·
(
UA
UR
)
-n
4
2
2
→ n = 2,5
< 0,5 → n = 0
Assistance needed? Please contact Jianghai Europe GmbH +49 (0) 2151 652088-72 or [email protected]
15
v2014.1