Date: Sun, 30 Nov 2014 11:11:42 -0500 From: Paul Pathiakis <pathiaki2@yahoo.com> To: John Johnstone <jjohnstone@tridentusa.com>, freebsd-questions@freebsd.org Subject: Re: UPS for FreeBSD Message-ID: <547B41BE.20700@yahoo.com> In-Reply-To: <547AAC20.1050006@tridentusa.com> References: <CAHieY7QGp2ELF-R91eu=vSrPsimVmVNJQ4kfucQ56PR7EEZmig@mail.gmail.com> <m57qdq$did$1@ger.gmane.org> <54777AB1.9010800@bluerosetech.com> <m581p1$65m$1@ger.gmane.org> <54779629.302@bluerosetech.com> <54789AF3.7090100@yahoo.com> <547AAC20.1050006@tridentusa.com>
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To all that responded on this thread: Thank you. I feel I have a better understanding of all this now. :-) The time spent to better educate others and myself is welcome and so "FreeBSD Community". P. On 11/30/2014 00:33, John Johnstone wrote: > I agree this thread is extremely long so I'll consolidate. > > On 11/28/14 10:55 AM, Paul Pathiakis via freebsd-questions wrote: >> Again, these UPSes are not double sine wave, they are stepped. You can >> get one for cheap, but, again, how much value do you place on your >> server and the information it has? If you're looking at APC, you have >> to look at their 'server class' UPS. They start (I think) at 1500VA and >> about $850. > > I think things could be clearer about the terms "double sine wave" and > "stepped". I think it should be made clear that although a UPS that > outputs a 60 Hz square wave is producing a poor approximation of a > sine wave, better designs still produce a sine wave in a stepped > fashion, just with a higher number of steps. One that produces an > infinite number of steps would be indistinguishable from a pure sine > wave. > > On 11/28/14 5:04 PM, Paul Pathiakis via freebsd-questions wrote: >> I found this which seems to be pretty solid. I believe it someone >> mentioned UltraUPS. >> >> http://www.controlledpwr.com/whitepapers/uutopla1.pdf > > This whitepaper refers to the stepped approximation of a pure sine > wave in their design: > > "The inverter reconstructs a sinewave from the DC using PWM (pulse width > modulation); a method that “digitizes” the DC into various width pulses > to make an AC sinewave." > > The number of steps needs to be high enough to not cause problems. > > On 11/27/14 2:25 PM, Darren Pilgrim wrote: >> Sine-wave approximating inverters do bad things to any power supply >> with a regulator cap (which is everything that won't catch fire on >> its own). The issue is the high frequency components and the >> hundreds of under- and over-voltage events per second inherent to the >> stepped square waveforms used (every step is a spike or sag). >> >> UPS manufactures know this is bad, so they try to hide it by calling >> it "modified sine wave", "quasi sine wave", "simulated sine wave", >> "PWM sinewave", etc., and hope you're dumb enough to fall for it. I >> have yet to see a consumer UPS that doesn't do this. > > I wouldn't say it fair to interpret UPS manufacturer's descriptions of > their methods of simulation as "hiding". > >> You need to buy a server-grade UPS to get something that won't damage >> your electronics. APC SmartUPS, Cyberpower PFC Sinewave or Smart >> App, Eaton 5P/PX or 9 series, Tripp Lite SmartOnline, etc. > > On 11/28/14 1:22 PM, Paul Pathiakis via freebsd-questions wrote: >> "Simulates" utility power. This is the sneaky little bit of >> marketing. Saying it's sine output.... It is, but it's simulated. >> I've been roped in by the APC marketing machine previously. > > As far as "simulated" being a bad thing, by definition all UPS's have > to simulate a sine wave once the AC power goes away. It is just a > question of how close an approximation is it. There's no question > that a 60 Hz square wave would be a poor approximation. > > As the number of steps increases, the magnitude of the "high frequency > components" and "under- and over-voltage events" becomes so small as > to be negligible. There are plenty of "server-grade" UPS's that > produce a step approximated simulated sine wave as the Controlled > Power whitepaper states. > > One aspect to consider is that if a UPS isn't an on-line design, any > negative effects experienced by the load due to the quality of the > output sine wave will only occur when the output is being produced by > the UPS during a power failure. It's reasonable to expect that this > is going to be a short interval which in many cases may not cause any > power supply problems. > > - > John J. > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "freebsd-questions-unsubscribe@freebsd.org"
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