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Yes, for power supplies certified >2000m please read the “note” in the spec.
In general, for unpotted models, a derating of 5°C/1000m has to be applied and for potted models, a derating of 3.5°C/1000m has to be applied.
For example LRS-75-24:
The datasheet shows:
The Note. 7 shows:
At 5000m the derating curve will need to move 15°C following the arrow (1)
At full load the maximum operating temperature at 5000m will be 35°C shown at (2)
Most small wattage and fanless power supplies are mainly installed in the horizontal position. If you have to install it vertically because of mechanical limitation, you should consider the output derating due to the heat concern. The temperature derating curve can be found on the spec sheet. Regarding the power supplies with built-in fan or the application has forced cooling system, vertical and horizontal installations have less difference. Ex. In SP-150 derating curve, the ambient temperature difference in application is 5 Celsius from vertical to horizontal. The output wattage in forced cooling can be 20% higher than air cooling convection.
In MEAN WELL’s specification you can find 2 derating curves, in below example the 300W open frame power supply: EPP-300
- The Derating Curve with the Ambient Temperature vs. Load
- The Derating Curve with the Input Voltage vs. Load
- In this Curve one can find that the maximum load of this power supply is 300W at 50dC when an external air flow of 20.5CFM is applied. For temperatures exceeding 50dC, 60dC for example additional derating need to be applied, in above case at 60dC the maximum load would be 225W. (50dC 300W, 70dC 150W => from 50dC to 60dC: 75W derating)
- In case this power supply would be used at 90VAC input, a derating of 80% must be applied. So, in previous example with the 20.5CFM forced air the max load would be 240W. In case of an ambient temperature of 60dC and a 90VAC input the maximum rated power would be 225W * 0.8 = 180W with 20.5CFM forced air.
- If the power supply is used in an application without additional forced Air, the power supply will be derated to 200W till a maximum temperature of 50dC
- In case it will be powered by a 90VAC input the power supply has to be additionally derated to 80% of the 200W = 160W max
1. To increase the reliability of the power supply, we suggest users choose a unit that has a rating of 30% more power than actual need. For example, if the system needs a 100W source, we suggest that users choose a power supply with 130W of output power or more. By doing this, you can effectively boost the reliability of the power supply in your system.
2. We also need to consider about ambient temperature of the power supply and whether there is additional device for dissipating the heat. If the power supply is working in a high temperature environment, we need to make some derating to the output power. The derating curve of “ambient temperature” versus “output power” can be found on our specifications.
3. Choosing functions based on your application:
- Protection function: Over Voltage Protection (OVP), Over Temperature Protection (OVP), Overload Protection (OLP), and etc.
- Application function: Signaling Function (Power Good, Power Fail), Remote Control, Remote Sensing, and etc.
- Special function: Power Factor Correction (PFC), Uninterruptible Power Supply (UPS) function.
4. Make sure that the model qualifies for the safety standards and EMC regulations you need.