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Thread: Active PFC Power Supply and NON true sine wave UPS.

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    Default Active PFC Power Supply and NON true sine wave UPS.

    I've recently been reading a lot about PSUs with Active PFC circuits having problems with UPS battery backups that don't output true sine wave power. I see a lot of conflicting information about how "bad" this can be for both the power supply and the UPS, as well as how vehemently this situation should be avoided. It seems to depend on the specific units involved (Enermax PSUs with PFC apparently don't work at all with non sine wave UPSs), but I'm totally unclear when it comes to other power supplies.

    I read that Silverstone, for example, "recommends" using a true sine wave UPS, but I just don't know what this really means in practice. Exactly what can potentially happen if a sine wave approximation UPS is used? Why is it "recommended" to use a sine wave UPS with this type of power supply, and just how strongly is it "recommended"? Given that 90% of UPSs are NOT true sine wave units, is this really as big an issue as some are saying.

    I'm using a Silverstone OP700, and don't yet have a new UPS for this system.

    Any feedback on this would be appreciated.

    Thanks,

    Larry

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    Get a UPS.

    You're going to do more damage with brown outs low volting a PSU than you are with a UPS with simulated sine wave.

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    Quote Originally Posted by jonnyGURU View Post
    Get a UPS.

    You're going to do more damage with brown outs low volting a PSU than you are with a UPS with simulated sine wave.
    I ALWAYS run my systems on UPSs -- this is not in question. The only question is how important it is to get a true sine wave UPS instead of a simulated sine wave model. After reading everything I could find on this, I'm totally unclear how "bad" it is to run an Active PFC power supply (OP700) on a simulated sine wave UPS. (I understand that it only makes a difference when on battery, but I don't want to do damage to anything in the events that this happens.)

    Thanks for clarification on this,

    Larry

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    Have you read any professional writings on this or just ramblings on forums?

    The only company that I've seen formally suggest true sine for a PSU is Enermax. But their PFC circuitry is funky to begin with.

    I haven't been able to figure out what a square or simulated sine wave would be bad for PFC circuits. Every single UPS I've deployed on the floor or in a rack have been simulated sine wave line interactive units and I have yet to have one fail. In fact, personally I've only had two PSU's fail on me in service: an Antec True Power with buldging secondary caps and an Enermax that overheated and died because one of the fans stopped running.

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    Quote Originally Posted by jonnyGURU View Post

    The only company that I've seen formally suggest true sine for a PSU is Enermax. But their PFC circuitry is funky to begin with.
    Speaking of the new Mod82+ does not have the mothra in a bug zapper APFC ignition sound.

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    Nice. Maybe they figured out why the Libertys and Infinitis exploded on the primary.

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    Thanks for the extra info.

    Quote Originally Posted by jonnyGURU View Post
    Have you read any professional writings on this or just ramblings on forums?
    Both. I just spoke with both Silverstone and APC. Silverstone is going to get back to me on this question, but APC was pretty clear -- they strongly felt that PFC power supplies should use true sine wave UPSs. They told me that the reason for this was because PFC power supplies require a much faster changeover time when the battery kicks in, and that due to the design of stepped sine wave UPSs, they were not always fast enough to satisfy the power supply. This could lead to the PSU shutting down when the battery tried to kick in. The guy I spoke with said that the stepped sine wave wouldn't "damage" the PSU, but that it simply might not work, and that if it DID work, it might not "always" work. Apparently it depends on the specific power supply.

    The only company that I've seen formally suggest true sine for a PSU is Enermax. But their PFC circuitry is funky to begin with.
    I've heard that both Silverstone and Corsair also "recommend" true sine wave UPSs for PFC supplies, but it's difficult to find any specific information on why they recommend this, or what could happen if you use a stepped sine wave UPS instead.

    I haven't been able to figure out what a square or simulated sine wave would be bad for PFC circuits. Every single UPS I've deployed on the floor or in a rack have been simulated sine wave line interactive units and I have yet to have one fail. In fact, personally I've only had two PSU's fail on me in service: an Antec True Power with buldging secondary caps and an Enermax that overheated and died because one of the fans stopped running.
    APC said that the issue is with the changeover when the battery kicks in, but that once the unit is on battery, it shouldn't be a problem.

    Thanks again for the feedback here,

    Larry

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    does APC even make any consumer level true sine-wave UPSs? Even their more expensive stuff seems to be stepped wave approximation

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    Quote Originally Posted by lalittle View Post
    They told me that the reason for this was because PFC power supplies require a much faster changeover time when the battery kicks in, and that due to the design of stepped sine wave UPSs, they were not always fast enough to satisfy the power supply.
    Whaaaaaaa???????

    Stop right there.

    That has NOTHING to do with the output's waveform.

    That's the difference between a line interactive and online UPS.

    A line interactive UPS switches between AC and battery. There's a milli-second transfer time, but some crappy PSU's will shut down when they see this.

    Online UPS's are always running off the DC to AC conversion whether there's AC from the mains or not, so there is no transfer time.

    Both of these are true regardless of sine wave.

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    I'll just toss this in.....I've got APC UPS units on my computers. The units are the BackUPS XS 900. One computer has a Corsair HX620 ps, one has an Ultra X3 1kw. Neither power supply has had any issues with the UPS units, and we have quite a few electricity shutdowns, "brownouts", and other weirdness out here....but we're in the country and our elect. service is not the greatest at all. Not unusual to see our lights flick off and on at random times.

    But we've never had any problems with the UPS and power supplies at all.....and we've had these particular UPS's running for the better part of a year now.
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