Choosing an Active-PFC PSU for use with stepped sine wave APC UPSs

mckamey

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Jan 19, 2012
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I have multiple APC UPSs which all output a "stepped approximation to a sine wave" when on battery power and the specs on my newest at least state up to an 8ms transfer time from line-power to battery-power.

I've had trouble with my Antec Earthwatts 500 PSU from day one. Typically a dip in power (rather than a full on outage) will cause my entire machine to immediately reboot. I've only recently realized this PSU/UPS combination is the culprit.

I believe that it is either the transfer time or the stepped sine wave approximation or both that are not mixing well. Some reviews blame it on the Active PCF, and others implied that the transfer time may be longer than the PSU will accept. In my older UPS many dips in power would cause a reset event. in my brand new UPS any dip will reset, and pulling the plug will reset but not allow it to reboot.

Since my UPSs represent the larger monetary investment and are newer, I figured I will replace the PSU to get one that is compatible. I've been researching and been unable to find any sort or metric to determine a brand or model that will work. Short of buying and returning until I find the right combo, I thought I'd ask.

I have the APC Back-UPS Pro 1000, APC Back-UPS XS 1500, and APC Back-UPS XS 1000. What kind of PSU should I be buying? I would love features like "silent", "efficient" or "powerful" but at this point I'd settle for "works", "doesn't burst into flames" and "doesn't cost an arm & a leg".
 
Solution
I use a Corsair Professional Series HX750W PSU with my APC Back-UPS XS 1300 which uses stepped approximation to a sine-wave and it works absolutely fine.

When X-bit Labs does their power supply reviews they test for UPS Compatibility with an APC SmartUPS SC 620 that uses stepped approximation to a sine-wave.
I use a Corsair Professional Series HX750W PSU with my APC Back-UPS XS 1300 which uses stepped approximation to a sine-wave and it works absolutely fine.

When X-bit Labs does their power supply reviews they test for UPS Compatibility with an APC SmartUPS SC 620 that uses stepped approximation to a sine-wave.
 
Solution

mckamey

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Jan 19, 2012
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Thanks ko888 for your reply. I read through a bunch of X-bit Labs' reviews. It gave me hope that my situation was more the exception than the rule.

Ultimately I ended up going with the Thermaltake TR2 500W (TR-500P). It is also Active-PFC but I think the 17ms minimum hold-up time helps it to survive the swap over to battery and it appears to run fine on the simulated sine wave UPS output.

My old PSU is the Antec EarthWatt EA 500 and it is fully incompatible with my APC Back-UPS Pro 1000 (i.e. will not run on battery and on previous UPS couldn't survive the swap to battery). So I was very pleased with this new PSU.

Thanks.
 

Jettbot

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Mar 14, 2012
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I'm having the same problem. I have 10 various APC UPS's from the Back UPS RS800 to the Back UPS RS 1000 & 1500. We have all sorts of power supplies in our workstations and servers but on our 2 main servers I have a Seasonic M12d 850w and in the other I have a Seasonic X-750w. I'd list the specs of the motherboards but its irrelevant as they are identical and I've tried trouble shooting this problem by isolating each component and it can only be the M12d that's giving me grief.

No matter what UPS is protecting the M12D 850w, the tiniest browout, and here in Bangkok we get many per day, will shut down that server. An identical server sitting next to it with an X-750 has no problem.

I even tried swapping which motherboard the M12d was connected to and it still had the same problem.

I can only surmise that the M12d does not like the stepped power that APC UPS's put out which sucks because I've had so many powerouts that I just lost a 10TB raid from constant rebuilds.

How do you find out about this crap, it's not documented from what I can tell. And a 1500VA UPS is way more than I need for this server but nothing seems to protect it.

Thanks

 

When X-bit Labs reviewed the Seasonic M12D 850W (M12D-850) it worked with their UPS.
UPS Compatibility

Together with an APC BackUPS SC 620 this PSU worked at loads up to 360W (from both the mains and the batteries). The pair switched to the batteries normally. The UPS was stable.

There's no guarantee that the power supply will work properly with a specific UPS until you test it for yourself. Just because it works for someone else does not guarantee that it'll work for you.

From Seasonic's Q & A:

Q: Will my new Seasonic PSU work with UPS? How powerful should be my UPS?

A: All Seasonic power supply units perfectly work with Online and Standby UPS and majority of Line-interactive UPS, providing up to 70~80% of their maximum Wattage. But some rare combinations of Seasonic power supplies and Line-interactive UPS might be working only at 50% of PSU’s max Wattage or be completely incompatible. The only way to be 100% sure is to check it with your UPS. As for the UPS Wattage, we recommend you to have it about 50~100% higher than your PSU Wattage.