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Thread: Can the PSU protect my components? Or do I need a UPS or a voltage regulator?

  1. #11
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    Quote Originally Posted by jonnyGURU View Post
    No. I won't excuse you.

    An AVR can protect from damage that's beyond what the PSU can handle. Period. Not every PSU is infallible. And when a power strip fails, you don't know until it's too late.
    I think you're mixing the surge protection issue with input voltage regulation issue.

    AVRs per si don't do surge protection. They usually incorpore a surge protector. But considering PSUs don't need to have the input voltage regulated (and all the issues caused by trying to do so), it's much better to plug it directly on the mains. Or use a dedicated surge protector (with no AVR).


    Quote Originally Posted by jonnyGURU View Post
    Corsair doesn't put that sticker on the box. I'm curious who is putting that on the box.
    The distributor or reseller, as said by Cyrix. AVRs are very common here.

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    As voltage drops, current increases. So I'd rather have an AVR boost my mains during a brown out. Especially when mains here are typically 110V. In 220V areas, I can see how it's less of an issue.

    Also, an AVR can remove EMI/RFI interference and noise from other hardware connected to the same circuit.

    And PSU's that have lower than spec hold up time can benefit. You say that the AVRs you've seen switch too slow.... Any of the ones I've used have the voltage corrected in a period of time that's much shorter than even an entry level PSU's hold up time. Of course, I'm talking about units from companies like APC and Tripp-Lite. Perhaps there are cheap AVRs down in Brazil that aren't as effective?

    The label seems to imply that damage can occur. For now, I completely fail to see how that's possible.

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    So I talked to RBuass and he pointed me to this video:

    https://www.youtube.com/watch?v=SfTc...ature=youtu.be

    He tells me that there are very crappy AVR's in Brazil that have switching times as slow as 33.3 mS: http://prnt.sc/dlh36n

    He said that the relay used inside these devices are not solid state and are similar to what's used in a car for a fuel pump, etc. These are products that you certainly do not see in the U.S.

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    Default Protection against crappy power

    As others have noted, if your computer isn't crashing during the brownouts, it's unlikely to be hurting your PSU.

    A typical PSU will operate with input voltages down to 90V (to handle the 100V mains voltage used in Japan). At low voltages, it needs to draw more current to provide the needed power, and that leads to increased heating of the primary-side switching components. But heating is a time-averaged effect, and power semiconductors are very unlikely to suffer lasting harm from a brief, infrequent, and moderate overload. In other words, it can do 120% of its rating for half a second.

    (This tolerance is exploited by cheap PSU manufacturers who put two 15A diodes in a PSU and claim it's rated for 40A.)

    Surges are something else. There are two kinds:
    1. "Swells" Increases in the supply voltage to well above normal for a few seconds. If you're in a 120V area, a PSU capable of handling 240V won't suffer. The main limitation is the 400V rating of the input components. 240V RMS rectifies to a peak of 340 VDC, so there's not a lot of headroom there before you start damaging the primary side filter capacitors or switching transistors.
    2. "Spikes", a.k.a. "transients" mostly caused by lightning. Brief impulses (measured in microseconds) of very high voltage. These are an issue, and a PSU is limited in how much it can do.
    Now, I've ranted about this before, but once more...

    The thing about lightning strikes is that they do not have a well-defined voltage. What they have is a well-defined current. A typical lightning strike is about 10,000 A, and a large one is 100,000. That current flows to the wet ground outside where the raindrops are falling, and the voltage is whatever it takes to make that current flow.

    The point is that it is not only literally impossible to stop this (with any insulator thinner than the quarter mile of air the bolt has already jumped through), but the harder you try, the more you'll suffer. The voltage will just rise until it does punch through.

    Just like boilers have relief valves, and explosives factories have at least one weak wall, the way to deal with this irresistible force is to not resist it, but give it somewhere safe to go. Carrying this current without damage is what the MOVs in a surge protector do. When the voltage rises above normal levels, they start passing ''huge'' amounts of current. This causes them to heat up very rapidly, but since spikes are brief and MOVs are (by the standards of electronic components) large and heat-resistant, they don't have time to get hot enough to melt.

    Anyway, a spike wants to spread. It comes in on one wire, and goes out ''every other wire'' to the outside world in search of ground. This is the mechanism by which spikes arrive at your computer in the first place: lightning hits a power line some miles away, and proceeds along the wires in both directions looking for a path to ground. It finds some paths down power poles, but spreads along every path to the large area of wet ground that is its ultimate destination. So it goes along power lines, through transformers, and to your house. There it spreads to every appliance looking for the easiest path to every form of ground.

    The current is divided by all this spreading out, but even 1% of a lightning strike is 100 A or more, and that's quite enough to fry electronics.

    So say you have a computer plugged in to AC power, and connected by an HDMI cable to a television, that is connected by a coaxial cable to a cable TV feed.

    Well, a spike coming in the AC power will divide itself between the AC neutral, the AC ground, and the coaxial cable. A few MOVs in your PSU can safely handle the first two, but can't do anything about the third. The spike will travel through your computer and through your TV, almost certainly damaging them in the process.

    This is why the essence of spike protection is to build an electrical "island" where every outside wire goes through the same surge protector. That gives spikes paths from every outside wire to every other wire. Remember, the spike's final destination is the wet ground outside where the raindrops have carried the charge from the clouds. If the shortest path to there is through the surge protector, then your computer is protected. (The Faraday cage is a similar concept.)

    Just remember that spikes are between wires. For every pair of wires connecting your computer to the outside world, ask where is the path that lets a spike get from one wire to the other without going through the protected equipment.

    A device connected only to the power line, whether it's called a "surge protector", "line conditioner", "power supply" or whatever can handle spikes between those three wires, but it can't help you with surges from those wires to any ''other'' wires (network cables, phone lines, HDMI cables, audio cables, etc.) that might be connected to your computer.

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    Quote Originally Posted by jonnyGURU View Post
    If you're only having brown outs that make the lights flicker, but the PSU stays on, then there's nothing happening to your computer parts and your PC isn't "slowly sacrificing itself".

    The PSU has a "bulk cap" that holds enough charge to keep the PSU live. If there's a brown out, this cap discharges slightly, but that's what caps do.

    The only part of a PSU that can "sacrifice" itself is if there is a lightning strike. There is a fuse and an MOV that, if there's a big enough spike, can blow rendering the PSU useless.
    Thanks for the quick answer.

    So you're saying that I can trust that Corsair PSU in providing "clean" power to my system? I really don't want to buy a UPS, too expensive, and obviously an overkill in my case. I've just read and watched some reviews about this APC voltage regulator, and it doesn't seem to be brilliant.

    The anomalies I've got in my flat are:
    - flickering lights
    - occasional buzzing noise from the headphone when plugged into the audio jack of a plugged in tablet.
    - When someone turns the lights on in the kitchen, the monitor in my room goes for a 1-2 secs.

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    Quote Originally Posted by za1234ki View Post
    Thanks for the quick answer.

    So you're saying that I can trust that Corsair PSU in providing "clean" power to my system? I really don't want to buy a UPS, too expensive, and obviously an overkill in my case. I've just read and watched some reviews about this APC voltage regulator, and it doesn't seem to be brilliant.

    The anomalies I've got in my flat are:
    - flickering lights
    - occasional buzzing noise from the headphone when plugged into the audio jack of a plugged in tablet.
    - When someone turns the lights on in the kitchen, the monitor in my room goes for a 1-2 secs.
    All the anomalies either point to your house or flat

    not having a good ground connection (that's that buzzing noise on the headphones) (although that would trip the RCD(as you call it in the UK))
    or a really bad power issue locally over the power lines,bad transformer?
    or maybe the wiring in your flat is old or may have issues that need to be fixed.

    UPS's are glorified surge suppressors with the added benefit, that has a built in battery that will let you shut down you computer or keep working for a little while even if the power is out.

    However after describing the anomalies you mentioned i would purchase a Surge Protector from APC, or Belkin, something well known. If you could find one with fireproof MOV's or ceramic encased ones then that's better (that's just my preference)

    At least it would deal with any problems before it hits your PSU until you figure out what's causing it.

    I saw this site and it has some good tips to figure out your power problems

    http://ask-the-electrician.com/elect...licker-or-dim/

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    I recommend to get a decent UPS, so you don#t have to worry so much about the PSU. The sticker is basically noch even telling half the story.

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    Quote Originally Posted by jonnyGURU View Post
    As voltage drops, current increases. So I'd rather have an AVR boost my mains during a brown out.
    And do you think this is really an issue?

    If the PSU can work with 90 VAC, case closed. If not, then the problem is your PSU.

    Quote Originally Posted by jonnyGURU View Post
    So I talked to RBuass and he pointed me to this video:

    https://www.youtube.com/watch?v=SfTc...ature=youtu.be

    He tells me that there are very crappy AVR's in Brazil that have switching times as slow as 33.3 mS: http://prnt.sc/dlh36n

    He said that the relay used inside these devices are not solid state and are similar to what's used in a car for a fuel pump, etc. These are products that you certainly do not see in the U.S.
    Maybe you have AVRs with some level of isolation and faster relays? Does this manage to stop the generation of the spikes caused when the relays (or whatever you're using) commute? And what about leaving the PSU with no input while the relays commute?

    These are the specs of a low cost AVR in Brazil (PDF): http://www.sms.com.br/aplicacoes/doc...familiaID=E027

    And now, looking to something from APC, we have this (PDF): http://www.apc.com/salestools/ASTE-6...7V37_R1_EN.pdf

    Response time on the two are the same, up to 2 AC cycles.

    At least the APC one works with 80 VAC input. The ones from SMS for 115/127 V need at least 91 or 93 VAC input. It's ridiculous if you consider a full range PSU can work with 90 VAC input, while the AVR not.

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    These line-interactive UPS are transforming the voltage using low-frequency transformers. It makes much sense, on the contrary, as the AVR function actually is usually implemented as couple taps from the same primary winding. There is no reason to make it able to correct much larger drops of the line voltage than about 20 %. Otherwise this primary winding itself (basically in auto-transformer mode) would have to be rated to handle the full power continuously, which would mean the transformer would have to be huge and expensive to handle that without melting. Cheap units on the other hand try to make use of very small transfomers, those of what I call as "Must Power origin" even have aluminium winding instead of copper (that's one of the reasons they haveso poor inverter efficiency). If the drop is larger, the UPS usually switches to the inverter and provides output power from accumulators.

    As for overvoltage, older UPSes just turned to yet another tap from the primary winding. Everything used to be switched using ordinary relays. Newer models I believe use semiconductors to lower the voltage and modulate the sine-wave so there is often just the tap to boost the voltage, but no other one (to lower it). There may be semiconductors used instead of ordinary relays, but generally this is either the case of high-end line-interactive UPSes, or on-line UPSes. Properly dimensed (for transient situations) high-power semiconductors for AC use (multi-layered components like triacs etc.) are not that cheap plus it lowers the efficiency as they have losses and need continuous cooling. You can not use ordinary FET for AC, that's the thing.

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