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I moved to an area/building where there are quite some problems with the wall-power supply. Primaraly I would like to protect my computers, secondary I would like have some affordable UPS for some of them.
Common advice is a online-ups systems, but they are expensive in the initial purchase, and also they use a considerable amount of power
A 90% efficient 1000W UPS for example, fully loaded, will consume 100W of power continuously.
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during the time that the power is ok, because they are constantly doing a power conversion subjected to loss.
There are some quite affordable "Line-Interactive" UPS around (which dont have much additional power consumption) but most of those have modified sine output, which appear to be dangerous for PCs with active pfc.
it's safe to use a non sine wave UPS in the US, or any other country where the line power is 120VAC ...... But I also tried to make another important point, it is ONLY safe if you are using a APFC PSU, this is because then there is only ONE input capacitor and it will be rated at 450VAC If you are using a Passive PFC or non PFC PSU you will have TWO capacitors, and a selector switch for 120VAC or 240VAC operation These capacitors will be rated for only 200VAC EACH In a country where the line power is 120VAC only ONE of the capacitors will be used But the square wave voltage will in the US be 470VAC/2=235VAC So that's why you need a APFC PSU, APFC PSU=450V capacitor Passive or non PFC PSU operated at 120VAC = 200VAC capacitor, too little for 235VAC square wave
The explanation behind the danger was based on some oscilloscope readings the output of such UPS, which contain besides quite blocky, quite high peaks at the block edges, that may kill some caps.
A general discussion on the topic of UPS and dangers to active pfc is interesting and can be found on many places, without a clear consensus (at least I didn't find it). So some clarification on that topic could be of interest, because conclusions seem controversial.
But at this point my main question is, if putting a voltage regulator behind such as "modified sine" ups, could prevent the damage by such peaks to PSUs with active pfc?
Sarmes
Posted 2014-11-19T12:25:44.447
Reputation: 121
@Sathya your edits removed some links to the references, i think the links are quite essential for the discussion. Thank you for your effort in editing, but i dont really consider the removing of the links and shortening of the quotes as improvements. Yes its shorter now, but less clear in my oppinion. – Sarmes – 2014-11-19T12:40:29.827
@Sathya Is the orriginal version of my post now completly lost, or is there some way how to retrieve it? – Sarmes – 2014-11-19T12:45:00.423
To my knowledge, the sine wave approximation only occurs when running on battery power. When the mains power is connected the output should be similar to normal AC. My UPS causes a buzzing sound due to sine wave approximation, but only if I disconnect the mains. If you buy a reasonable make and model (e.g. an APC SMART UPS, about $500) then I really don't think you should have any problems since people are using them all the time for critical situations. The cheap consumer voltage regulators you are talking about do not turn the input into a pure sine wave, they simply prevent spikes. – James P – 2014-11-19T12:49:24.997
there were 4 references when I started editing - they are still there - the http was left out, so the parser wasn't linking them. Corrected that. You can see all revisions at http://superuser.com/posts/842187/revisions
– Sathyajith Bhat – 2014-11-19T12:49:27.557@Sathya i see the links in the bottom when i edit, but i dont see them in the normal text. Whithout the links, people miss an important the point of the question e.g. James – Sarmes – 2014-11-19T12:52:37.853
@Sarmes the links are highlighted in blue colour on the post. – Sathyajith Bhat – 2014-11-19T12:59:39.673
@Sathya Now its makes sense, perfect! – Sarmes – 2014-11-19T13:01:03.113
@James according to several sources the sine wave approximation can damage PSUs with active pfc in areas where voltage is not 110-120 Volts such as in europe, (see for example the complete forum post but especially the contribution of of Per Hansson 04-01-2008, 04:23 PM @ www.jonnyguru.com/forums/archive/index.php/t-3964.htm ) the problem is not the block shape of the signal, but the spikes at the edges of the blocks (see the osciloscope readings). I was hoping that the voltage regulator could "take away those spikes". – – Sarmes – 2014-11-19T13:07:57.607
Do you already have "active PFC" systems, or are you simply considering them? There's no real point in an individual having an active PFC system -- it saves you little if any money (and may even consume a hair more power). The reason for having them would be in a large business where it would save the business power factor surcharges. – Daniel R Hicks – 2014-11-19T13:15:37.750
A "voltage regulator", unless it's specifically a sine wave output version, is apt to make the waveform worse. – Daniel R Hicks – 2014-11-19T13:17:36.450
@Daniel R Hicks, Already have PSUs with active pfc (whithout knowing actualy), it seems to be quite standard on silver/gold rated psu's. (why did i go those psu's? Not for saving electricity to be honest, i thought that since they are powering expensive hardware, it would be safer, since i once had a fried mobo due a broken psu, and these psus have higher mtbf) – Sarmes – 2014-11-19T13:27:45.467
@DanielRHicks, could you explain/or provide a reference why it would make the waveform worse? – Sarmes – 2014-11-19T13:36:33.560
Just what I've read over the past 50 years or so. A "voltage regulator" must somehow modify the incoming power to maintain the target voltage. It can do this various ways, from "chopping" the incoming power to "bucking" or "boosting" the voltage with a transformer. These techniques modify the waveform, and not for the better. Those using a "saturable reactor" (the old heavy-iron school of voltage regulation) can actually increase the peak voltage by 30 volts or so over a sine wave. Newer models, using semiconductors, must somehow chop or clip the incoming sine wave to limit it's peak. – Daniel R Hicks – 2014-11-19T13:59:08.153
@Sarmes: Different UPS models will obviously produce different results. I suspect that the two that were tested were low end models. If you contact APC, they should be able to confirm that Smart UPS range is fine for PFC PSU's. Also they offer a connected equipment guarantee that means they would be liable to offer compensation if your device was damaged. – James P – 2014-11-19T14:15:53.977
Wikipedia even has a picture of the waveform of one of the models (SMT1500I) at http://en.m.wikipedia.org/wiki/APC_Smart-UPS
– James P – 2014-11-19T14:21:18.027@James, yes that picture is of an "expensive" true sine wave UPS. In the the table next to the picture on the Wikipedia link there is a statement, related to my question about the less expensive types of UPS where i was speaking about (in the case of APC "Smart-UPS SC": "A simplified version of the Smart-UPS, with modified square wave output (and thus incompatible with many active PFC PC power supplies" My aim was basically to use the cheaper UPS, with an aditional regulator to protect the APFC PSU. – Sarmes – 2014-11-19T14:36:37.003
@DanielRHicks It wasnt that i didnt believe you, but it seemed quite suprizing to me, that a regulator makes things/peaks worse. Is there any reason to use a regulator to protect equipment over a surge protector? (now speaking about the case whitout a UPS). Before i had a server with a power supply that if i unplugged it, would leave the computer running for another 2-3 seconds or so, i dont know how that feature was called, but when i read today about voltage regulators, i thought them to be some sort of smoothing-buffer, like that. – Sarmes – 2014-11-19T14:39:48.883
@DanielRHicks during my ongoing search i found a thread in another forum, dealing with a very similar question, in which a similar solution as in my question was propoased: http://www.tomshardware.co.uk/forum/352692-28-will-corsair-work-sinwave-square-wave commend of Quaddro 9 November 2012 02:08:26 I dont want to make it in to a yes-no discussion, im just looking for the answere, and i want to understand it.
– Sarmes – 2014-11-19T15:21:01.317@Sarmes: Are you sure that these higher end UPS models will actually work out that much more expensive for you? Firstly you won't need to buy any voltage regulators (which probably won't help anyway) and secondly you should be able to plug in more PC's to one unit than you could with a cheaper model. – James P – 2014-11-19T19:44:53.837
@James, well there is a significant price difference, but since i cant find a clear answere on my question, i think i will go for used line interactive UPS that have sine wave output, with new batteries. But im a bit suprized that there are different oppinions on the effect of these voltage regulators. – Sarmes – 2014-12-02T08:22:09.783