Life Time Estimation Lifetime Estimation of Electrolytic Aluminum Capacitors from Jianghai To estimate the Lifetime of a non-solid Electrolytic Aluminum Capacitor from Jianghai, the following formulas can be utilized. The Lifetime depends mainly on the ambient temperature, the ripple current and the rated 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: LX = L0 · KT · KR · KV Where: LX L0 KT KR KV 1. Total Lifetime Lifetime under Rated Ripple Current at Upper Category Temperature (see catalogue) Temperature Factor Ripple Current Factor 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 - TX KT = 2 10K Where: 2. T0 Rated Temperature TX Actual Operational Temperature KR Ripple Current Factor: The influence of ripple current on Lifetime can be estimated according to the following formula: KR = Ki With: A= 1 – A ∆ T0 10K () I I0 2 Where: I Actual Rated Ripple Current I0 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 Safety Coefficient, defined as T0 = 105°C I > I0: Ki = 4 I ≤ I0: Ki = 2 Ki = 2 T0 = 85°C 14 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, the operational voltage will affect their Lifetime. It is expressed as follows: KV = Where: UR n UX ( ) UR Rated Voltage UX Actual Operation Voltage n Coefficient, defined as: 1≤ 1,25 < 2< UR UX UR UX ≤ 1,25 → n = 5 ≤2 →n=3 →n=1 UR UX 4. Frequency Correction Factors: If the actual Ripple Currents I are not given at the same frequency like I0, weighing factors need to be applied. If 1 + Ff 1 I If1 ... Ifn Ff1 ...Ffn If 2 ( ) ( ) I= 2 2 Ff 2 + ... If n ( ) 2 Ff n Actual Rated Ripple Current at different frequencies Ripple Current at different frequencies Frequency Correction Factors for different frequencies 5. JIANGHAI Electrolytic Capacitor Lifetime Estimation Formula LX = L0 · KT · KR · KV T0-Tx = L0· 2 10K I · Ki 2 [1- ( I ) ]· 0 ∆ T0 10K · UR n (U ) X T0 = 105°C T0 = 85°C I > I0 → Ki = 4 I ≤ I0 → Ki = 2 → Ki = 2 ≤ UR ≤ UX 1,25 → n = 5 1,25 < UR ≤ UX 2 → n = 3 2 UR UX 1 < → n = 1 Assistance needed? Please contact Jianghai Europe GmbH +49 (0) 2151 652088-72 or [email protected] 15