Date: Mon, 1 Dec 2014 12:39:24 -0500 From: Alejandro Imass <aimass@yabarana.com> To: John Johnstone <jjohnstone@tridentusa.com> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: UPS for FreeBSD Message-ID: <CAHieY7QqeUGUiOfMZyOkVkunWyBO7izX=a_2rxYgu1eYrmBhgA@mail.gmail.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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On Sun, Nov 30, 2014 at 12:33 AM, John Johnstone <jjohnstone@tridentusa.com> wrote: > I agree this thread is extremely long so I'll consolidate. > > > [...] > 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. > > Why do switching power supplies really care about the input wave form? Most switching power supplies rectify with a full bridge and capacitors and then switch from that rectified DC so why would it care about the incoming waveform? So long as it's oscillating, square, sine or triangular should work just the same. I think HF components would get filtered by design in the first few stages of the switching PS so I don't understand why pure, or close to pure sine wave is really important. What components are really at risk from poor sine-wave inverter? Besides, UPS are designed to power the equipment for a short period (either to shut-down or activate a backup generator), so in reality there is that much more risk by using a cheaper UPS? IS the price difference really worth it? Or is it all technical mumbo-jumbo to charge a lot more for "pure sine wave", which honestly does NOT need sophisticated components like someone said. It can be accomplished with a simple saw-tooth (with 2 OP-Amps one as integrator and another one as comparator) and a low-pass filter (a coil of wire). Inverter circuitry is really not that complex and good sine-wave approximations are not that hard to do. I am pretty sure a typical switching PS will do just fine if you feed the square wave or an unfiltered saw-tooth sine wave into it. Anyway just MHO. Best, Alejandro Imass
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