Hey Arjen, hope you're doing fine.
2011/4/16 Arjen de Korte <[email protected]> > Citeren Arnaud Quette <[email protected]>: > > > we (Eaton) have created a new data to expose efficiency of the UPS >> (basically it is the ratio of the output current on the input current). >> I know that at least APC should also provide it on some units, since I've >> seen evidence in an EPA presentation [1]. >> >> So I'd like to create the following new data: >> >> - Name: ups.efficiency >> - Description: Efficiency of the UPS (ratio of the output current on the >> input current) (percent) >> - Example value: 99 >> >> As usual, comments and feedback are very welcome... >> > > Two comments: > > 1) What would be reported if the UPS is running on battery? There clearly > would be no input power at that time. What is reported in that case? > in Eaton implementation, switching to battery gives an "ups.efficiency = 0" > 2) Calculating the efficiency based on the ratio of input and output > *current* leaves a giant loophole to artificially increase the reported > efficiency. On an online UPS one could increase the 'efficiency' by setting > the output voltage a few percent above the input voltage. Similarly, if a > system would have a near unity power factor on the input, but a crappy one > on the output, you'd also inflate the reported efficiency by using the RMS > figures. > indeed. and that's what we'll get if marketing takes over engineering. note that the standard disclaimer on device's data applies: this is not a lab measurements tool. Data are only approximations... as for Eaton implementation, I don't have the exact formula used in Eaton devices, but this is an approximation that also takes in account some percentage loss. As an example, here is a data excerpt of what I have with a unit here: (...) ups.efficiency: 72 ups.load: 13 ups.power: 209 ups.power.nominal: 1500 ups.realpower: 108 ups.realpower.nominal: 1350 ups.type: offline / line interactive (...) note that this unit is a line interactive. I'd only see some merit in reporting this, if it would be the ratio of input > and output real power values. I would be surprised if in a real world > scenario however if one would get very close to 99% (if not in running in > bypass mode). A more typical value of a double conversion UPS would be > something between 90-95% and even then only when the UPS is properly scaled > for the designed load. The good thing would be that people might be made > aware how much power they are wasting, given that fact that in many cases a > UPS will not be operated near the optimum efficieny load. > indeed. I at least consider this as a first step in the right direction. And it's also true that the example value may seem like a troll (putting something like 92 % would probably be more suitable). As for a 99 % efficiency, apart from running on bypass, I only know units like Eaton 9395, that have internal modules powered up or down depending on the ups load. which helps a lot in improving efficiency. cheers, Arnaud -- Linux / Unix Expert R&D - Eaton - http://powerquality.eaton.com Network UPS Tools (NUT) Project Leader - http://www.networkupstools.org/ Debian Developer - http://www.debian.org Free Software Developer - http://arnaud.quette.free.fr/
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