Date: Tue, 2 Dec 2014 19:22:52 +0800 From: Erich Dollansky <erichsfreebsdlist@alogt.com> To: Alejandro Imass <aimass@yabarana.com> Cc: John Johnstone <jjohnstone@tridentusa.com>, FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: UPS for FreeBSD Message-ID: <20141202192252.7cab41b5@X220.alogt.com> In-Reply-To: <CAHieY7RZ21eR2R6SfSkNDaOabvL4FzOJfKFa-uDG=DdxdVGosg@mail.gmail.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> <CAHieY7QqeUGUiOfMZyOkVkunWyBO7izX=a_2rxYgu1eYrmBhgA@mail.gmail.com> <20141202103847.564806a2@X220.alogt.com> <CAHieY7RZ21eR2R6SfSkNDaOabvL4FzOJfKFa-uDG=DdxdVGosg@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Hi, On Mon, 1 Dec 2014 22:46:58 -0500 Alejandro Imass <aimass@yabarana.com> wrote: > On Mon, Dec 1, 2014 at 9:38 PM, Erich Dollansky > <erichsfreebsdlist@alogt.com > > wrote: > > > On Mon, 1 Dec 2014 12:39:24 -0500 > > Alejandro Imass <aimass@yabarana.com> wrote: > > > > > On Sun, Nov 30, 2014 at 12:33 AM, John Johnstone > > > <jjohnstone@tridentusa.com> wrote: > > > > > the average volage over a square is much higher than over a sine. If > > the components are not designed for this, they will fail. You can > > see this effect by connecting a light bulb to an UPS and switch > > mains off an on again. The smaller the difference in brightness > > gets, the better the UPS emulates a sine. Of course, the life time > > of the light bulb gets reduced. > > > > > Should not be a problem for any modern switching power supply. In > fact the higher the RMS the more efficient it will operate. The RMS > of the sine x/SQRT(2) of a square wave is just x, where x is the peak > to peak voltage. The peak to peak of 120V is around 170V which is > just fine for most switching power supplies which are rated for about > 250V RMS. It _could_ be a bit of a problem is the UPS is for 240V but > I have never personally seen one in a North American store. Besides > any 240V UPS manufacturer would have to know this and honestly I > don't really think that any UPS uses a square wave. > the world is a bit bigger than the USA. > I will be sure to test this with an oscilloscope when I finally buy > the UPS that started this thread - I promise I will buy the cheapest > one I find and post pictures of the output waveform ;-) > There are sites which do this already. I just do not have URLs at hand. They normally do not do a simple squere but use i.e. 3 squares. The higher the price gets, the smaller the squares will get. > [...] > > > > This is the question. Most power supplies will be able to handle the > > square waveform. Escpecially modern power supplies being able to > > handle any voltage from 100 to 250V. > > > > > Actually I was referring to another comment that suggested that HF > harmonics from saw-tooth emulation or square wave "ring" could somehow > affect the switching PS of a typical computer. I think this is > unlikely because it will get filtered by the first rectification > circuitry of the switching power supply (I am no expert and could be > wrong and maybe some switching PS would be sensitive to this, but I > really doubt it). HF does affect some transformers and linear > equipment and still is very unlikely. > Yes, it should be like this. > [..] > > > > It is the volume. When the cheaper UPSes appeared, their price > > advantage was pretty minor. > > > > I wonder meanwhile if it is not cheaper to use an inverter used in > > solar panel installations. At least for larger inverters, they have > > a clear price advantage but require batteries which are not > > available at the next corner shop. > > > > The problem I think is the switch-over speed. It would be really cool > to find UPS that use *any* external battery, and you could just use a > car battery for example which is very reliable, durable and readily > available. > Oh, I did this once for a client at a very remote location. He only has had a lousy generator but wanted to run a normal PC in a decent manner without spending too much money. We took the a cheap car battery charger, two car batteries and an off-shelve inverter to be used in a truck. Nothing can beat this as the UPS is always on. So no switch over. The clear disadvantage are the batteries. Car batteries are designed for a high load for a short period of time. The result with a low load over a longer period of time is bad. The best I have seen yet are batteries used for solar panels. The quality of the batteries is really outstanding. The price is even more outstanding. Erich
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20141202192252.7cab41b5>