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| Power Factor Correction and Servers |
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| Halcyon:
I noticed an option in the BIOS for a newer Dell server, that allow you to turn PFC on or off. It's not something you usually see in this type of equipment. Why would someone want to turn PFC off? Does it have some kind of drawback that I'm not aware of? |
| Monkeh:
Apparently it increases standby power consumption. I'm not quite sure who has a use-case for large numbers of servers sat powered off, but apparently someone wanted it enough for Dell to do it.. |
| NiHaoMike:
Having PFC on increases power use at light load. Some UPS systems perform the PFC function and since the UPS would be rated for the maximum VA draw, the increased current at low load would not be a problem. That said, it probably would be more accurate to make the choices "Auto" and "Always On" since PFC will always have to operate under significant load. |
| Miyuki:
Either a light load (what should be solved automatically by the PFC controller) Or a UPS issue. This sounds more plausible. You can even decide to use non-sinusoidal output on UPS as this will increase efficiency. But most PCF controllers will go crazy with it. There are even some UPS systems that provide DC, but it tends to be on lower voltages as it is a hustle to fuse or disconnect 300-400V DC It is a pure waste to make UPS for servers to produce pure sine as nothing there use AC and they you have to convert it against back to DC with PFC //edit But the manual says it decrease consumption in Sleep mode |
| Marco:
I see minus 48v as server power, why minus? |
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