Conclusion
Derating calculations are only as reliable as the data they are derived from. Additionally, they are based on several assumptions. Consequently, real-life testing is needed to generate precise parameter values and accurate derating curves.
Automating this process guarantees repeatability and can speed up the testing significantly. For instance, in order to properly characterize a power supply, measuring the maximum temperature of multiple critical components manually at different airflow rates used to take several days. Now, accurate derating curves can be generated in a matter of hours, thanks to automated processes.
When a user installs a power supply in harsh operating conditions with high ambient temperatures, they have to understand that the lifetime of the device will be significantly reduced. Nevertheless, there may be situations where the power supply needs to be pushed to the extremes of its operating envelope, but this must be done without risking catastrophic failure such as thermal runaway or burnt-out components. However, knowing that the derating curve is measured rather than calculated renders a degree of confidence by implying that the power supply will survive such extreme events without failing in the process.
Our tests also revealed that different components reach their maximum temperature limits under different operating conditions. For example, at low air flow, the temperature of the input bulk capacitor could be the “weakest link” that limits the output power. However, at higher air flows, vortex shedding around the cylindrical shape of the capacitor increases the effective heat transfer rate and a different component (typically, the switching transistor) reaches its critical maximum temperature before the capacitor. Such real-life variabilities are difficult, if not nearly impossible, to simulate accurately using thermal flow modelling, but by using multiple hot-spot IR thermal imaging, the RECOM system can automatically selects the most critical component and uses that to control the load.
Thus, derating curves are not always similar for the same power supply under different operating conditions. For RECOM customers who need reassurance that our power supplies will not be pushed beyond their limits under extreme conditions, we can program our wind tunnel set-up to replicate those operating states and give a clear pass/fail reply.
[1] If you think the title sounds familiar, Kurt Cobain sang the line "I’d rather be dead than cool" in the track Stay Away in his album Nevermind by Nirvana. He achieved both, of course.
Automating this process guarantees repeatability and can speed up the testing significantly. For instance, in order to properly characterize a power supply, measuring the maximum temperature of multiple critical components manually at different airflow rates used to take several days. Now, accurate derating curves can be generated in a matter of hours, thanks to automated processes.
When a user installs a power supply in harsh operating conditions with high ambient temperatures, they have to understand that the lifetime of the device will be significantly reduced. Nevertheless, there may be situations where the power supply needs to be pushed to the extremes of its operating envelope, but this must be done without risking catastrophic failure such as thermal runaway or burnt-out components. However, knowing that the derating curve is measured rather than calculated renders a degree of confidence by implying that the power supply will survive such extreme events without failing in the process.
Our tests also revealed that different components reach their maximum temperature limits under different operating conditions. For example, at low air flow, the temperature of the input bulk capacitor could be the “weakest link” that limits the output power. However, at higher air flows, vortex shedding around the cylindrical shape of the capacitor increases the effective heat transfer rate and a different component (typically, the switching transistor) reaches its critical maximum temperature before the capacitor. Such real-life variabilities are difficult, if not nearly impossible, to simulate accurately using thermal flow modelling, but by using multiple hot-spot IR thermal imaging, the RECOM system can automatically selects the most critical component and uses that to control the load.
Thus, derating curves are not always similar for the same power supply under different operating conditions. For RECOM customers who need reassurance that our power supplies will not be pushed beyond their limits under extreme conditions, we can program our wind tunnel set-up to replicate those operating states and give a clear pass/fail reply.
[1] If you think the title sounds familiar, Kurt Cobain sang the line "I’d rather be dead than cool" in the track Stay Away in his album Nevermind by Nirvana. He achieved both, of course.
