Reliability and service life of MEAN WELL power supplies

Among the significant characteristics of power supplies that influence the decision to choose one or another series are information about the warranty period for the model, its reliability and service life. And if the warranty period is quite accurately defined in the Specification for a series of power supplies from MEAN WELL, then there is no such unambiguity with the assessment of reliability and determination of the service life for a number of reasons.

Any electronic devices, including power supplies, have an uneven failure rate (Failure Rate) during their life cycle.

Failure rate in different periods of operation

The greatest number of failures occurs at the device initialization stage - when the finished power supply is turned on for the first time and its characteristics are checked. This number of failures can be minimized by careful control of incoming components, streamlined production and random batch testing (for a number of series, the manufacturer conducts 100% initial testing of assembled power supplies and converters). When all the initial failures have already shown themselves, a rather long (many-year) period of random failures sets in. At this stage, due to the adopted technological solutions, selected components and topology, failures are possible, but their number does not exceed a certain acceptable and economically feasible level for the manufacturer. Further, with time of physical wear and obsolescence of materials and components (their degradation due to operating conditions), the failure rate increases over time. In other words, at this stage, the life of the power supply comes to an end.

What factors most affect the reliability of a power supply and its performance?

• temperature . This includes both the ambient temperature itself and the ventilation conditions of the power supplies. The better the conditions for air convection and the more stable the ambient temperature, the better.
• Humidity and steam . The higher the humidity values, the higher the risk of failure of the power supply. Fluctuations in the temperature of the medium, when condensation is possible, also affect in a similar way. Therefore, when choosing a power source, it is advisable to pay attention to the degree of protection of the IP case (if any), or to fill the device with a protective compound partially or entirely (potted, semi-potted, indicated in the Specification for the series).
• Dust . Using the power supply in dusty environments can lead to direct failure of the components in the power supply, such as a cooling fan, or cause insulation failure between individual nodes. Therefore, it is advisable to provide dust protection for the power supply, for example, by using an additional dust filter, as well as to carry out periodic inspection and cleaning.
• Vibrations and shock loads . Exposure to this factor can lead to mechanical wear of the components and the power supply assembly, such as physical damage to winding components, solder points, loosening of wires in connectors, etc.
• electromagnetic field . It is important to take into account both the direct location of sources of strong electric and / or magnetic fields in the area where the power source is located, as well as the change in the directions of these fields during the operation of such equipment. Most power supplies have a number of protections (including overvoltage), but these protections are not always able to fully protect the power supply itself, or adverse electromagnetic conditions can significantly reduce its service life.

The main characteristic that determines the reliability of MEAN WELL power supplies is the mean time between failures (Mean Time Before Failure, MTBF), expressed in hours of operation, using the example of power supplies of the ELG-150 series . MTBF in specification

MTBF is an expected value intended to predict reliability. MTBF is the average operating time until the reliability of the product drops to 36.8%. For example, if the MTBF of a product is 20,000 hours, this does not mean that this product can be used for 20,000 hours, but rather that after using for 20,000 hours, the probability of its operation is 36.8% (e ^-1 = 0.368 ). The mean time between failures and the probability of correct operation (reliability) are directly related by the relations:

MTBF and Reliability

Mean Time Between Failures (MTBF) can be calculated using two different techniques: component based calculations and stress testing. MEAN WELL typically uses two standards for MTBF calculation, MIL-HDBK-217F and TELCORDIA SR/TR-332 (Bellcore).

MEAN WELL does not directly standardize the service life of power supplies and does not indicate it in the Specification, since this value completely depends on the operating conditions presented above. In a simplified form, the service life of a device is determined based on the dependence of the service life of its components on the ambient temperature and load level. Therefore, for each device, the most critical component is determined and a lifetime calculation is made based on the lifetime of this component under various conditions. For example, from the Test Report for EDR-120-24, such a component is an electrolytic capacitor in one of the circuits:

Estimated life of the most critical component for EDR-120-24

In some cases, the test report also indicates the expected service life obtained on the basis of accelerated testing (Accelerated Life Test), for the example of the same EDR-120-24, it is about 50 thousand hours, which is about 5 and a half years in operation 24/7/365. But this is more of an estimate than a fact.

For questions related to the selection and use of MEAN WELL products, please contact Meanwell@chipdip.ru .