X2:Can be found in chi-square distribution.This method compares to the previous methods, this calculation uses real test data to demonstrate the reliability of the power supply. Please refer to the following equation for MTBF calculation. If the power supply is continuously used at double the MTBF time, the probability of proper operation becomes 13.5%(e-2=0.135.ĭMTBF (Demonstrated Mean Time Between Failures) is a way of evaluating MTBF in a relatively short period of time based on accelerated deterioration (high stress, high temperature) tests under specific parameters and conditions. Currently MEAN WELL is adopting MIL-HDBK-217F, to predict the expected reliability through Stress Analysis (excluding fans) this MTBF means the probability of the product can continue the normal work after working continuously up to the calculated MTBF time is 36.8% (e-1=0.368). The exact meaning of MTBF is, after continuously using the power supply for a certain amount of time, the average time that the probability of proper operation is down to 36.8%(e-1=0.368). MEAN WELL utilize MIL-HDBK-217F(Stress Analysis) as the core of MTBF. MIL-HDBK-217F is a United States military standard, and TELCORDIA SR/TR-332(Bellcore) is a commercial regulation. The regulations, MIL-HDBK-217F Notice 2 and TELCORDIA SR/TR-332(Bellcore) are commonly used to calculate MTBF. MTBF can be calculated by two different methodologies, which are “part count” and “stress analysis”. Please note the attached German and English PDFs which hold all the above information for print-out.MTBF (Mean Time Between Failure) and Life Cycle are both indicators of reliability. Gottschalk, Armin: Qualitäts- und Zuverlässigkeitssicherung elektronischer Bauelemente und Systeme, ISBN, 978-3-8169-2680-1 The MTBF value should not be confused with the minimum service life of a system. For the development engineer, these values allow to validate the failure rates of the complete system in order to select other components if necessary or to start a redesign. The values of the analysis must be considered as pure statistical values. The MTBF value is specified in the chapter "Specifications / Standards" of the "Hardware Reference" corresponding to the controller.Įxample: Extract of chapter "2.5 Standards" of the "EPOS4 Module-Compact 24-1_5 Hardware Reference.pdf" manual: This finally means that the specified total MTBF-value match very precisely the reality. The remaining passive components are calculated according to the MIL-HDBK-217F handbook. That is the reason why we calculate with these effective FIT-values. Active components have a predominant influence on the resulting MTBF-value of a product. These FIT-values are preferred for calculating the MTBF of maxon controllers, because they allow a more accurate calculation than the general values from handbooks. Producers of electronic components identify the effective FIT-value with so-called accelerated tests according to the Arrhenius law. They are based on international standards such as:īased on parts lists, the MTBF value is calculated for each part, considering as well external factors such as ambient temperature, humidity or stress. Manuals are used to get realistic MTBF values close to the later experience in the field. Besides the time for repairing, it includes the time for failure analysis as well. MTTR is the average time needed for repair (= Mean Time to Repair). It is used for systems that cannot be repaired the device directly enters the recycling process. The term MTTF (= Mean Time To Failure) differs only slightly from MTBF. Therefore, MTBF values are determined with the help of manuals that include these conditions. A large influence comes from the ambient conditions such as temperature variations, vibrations, and so on. Summing the MTBF values of single components or subassemblies gives the MTBF of the full system. The MTBF results from the inverse FIT or λ values. Failure rates are identified by means of life testing experiments and experience from the field. Typical values lie between 300‘000 and 1‘200‘000 hours. The MTBF value (= Mean Time Between Failure) is defined as the time between two errors of an assembly or device. Phase 3, the deterioration phase, is hardly relevant for electronic components.Īssuming that the failure rate λ is approximately constant, the equation can be simplified as follows: In this second phase, the standard failure rates for electronics components are defined and calculated. In the second phase, the admissible failures are defined, usually with a constant rate over time. In the first phase, one finds the early failure due to weakness in the materials, quality variations in production, handling mistakes and spurious, unconfirmed failures. Where to find the MTBF value of maxon controllers?Įach component has a failure rate curve in the shape of a bath tube, called Weibull distribution.How is reliability calculated for maxon controllers?.
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