PFC & Sine Wave UPS Interactions?

[qdemn7]

Since I'm seriously considering on buying a Sine-Wave UPS, I want to know can there be any type of problems using a Power Supply with Power Factor Correction and a Sine Wave or Double Conversion UPS? No type of feedback between the two trying to (over)correct for bad power? Any problems at all?

 

[dandragonrage]

No problems.

 

[t5brick]

i don't know a whole lot about Sine-Wave UPS units. from what i've read, they simply make sure the output is a Sine wave, they do nothing for power factor. power factor is when the voltage and current sine waves aren't aligned. you can guess what a PFC does.

i'd say that they'll work together to correct 2 different problems.

 

[jasonlitka]

As long as the UPS you buy outputs a TRUE sine wave there isn't a problem. If it outputs a stepped sine wave then you might ruin into issues. There are some issues betwen high-quality PSUs (like those from PCP&C) and cheaper UPSs (like APC's Back-UPS models). I'd suggest a nice UPS from APC's Smart-UPS line. I have never had any problems with them (except the price).

 

[gee]

As long as the UPS you buy outputs a TRUE sine wave there isn't a problem. If it outputs a stepped sine wave then you might ruin into issues. There are some issues betwen high-quality PSUs (like those from PCP&C) and cheaper UPSs (like APC's Back-UPS models). I'd suggest a nice UPS from APC's Smart-UPS line. I have never had any problems with them (except the price).

very few UPSes put out stepped sine waves; most non-sine UPSes (eg, APC BackUPS units) put out a filtered square wave which is more like a "fatter" sine wave. And switching power supplies actually *prefer* this non-sine waveform over a true sine wave. The non-sine waveforms reduce the ripple current in the input capacitors and input rectifier.

PFC circuits won't care what you give them, as long as it's not a pure square wave or anything.

Oh, and this is coming from someone who designs power supplies as part of his day job...

 

[Ice Czar]

thats the second time you mentioned modfiied sinewaves being better than pure
was wondering if maybe you like to cook up a UPS FAQ with some juicy linkage?

 

[qdemn7]

very few UPSes put out stepped sine waves; most non-sine UPSes (eg, APC BackUPS units) put out a filtered square wave which is more like a "fatter" sine wave. And switching power supplies actually *prefer* this non-sine waveform over a true sine wave. The non-sine waveforms reduce the ripple current in the input capacitors and input rectifier.

PFC circuits won't care what you give them, as long as it's not a pure square wave or anything.

Oh, and this is coming from someone who designs power supplies as part of his day job...

OK, thanks for that info. From what you're saying it sounds like I don't really need to spend the extra money on a "pure" sine wave UPS as long as the switchover time is low enough.

thats the second time you mentioned modfiied sinewaves being better than pure
was wondering if maybe you like to cook up a UPS FAQ with some juicy linkage?

Yes please, it's always best to hear from a professional in this area. And this would be save a lot of time in the future with people posting questions.

IMO, power supplies and UPS are one of the areas of enthusiast computing that tend to be ignored, unless it's about someone sleeving their PS. People will spend $500 on the latest video card, or $1000 or the latest CPU but then buy a POS PS, and won't even invest in a UPS or even surge protector.

 

[gee]

thats the second time you mentioned modfiied sinewaves being better than pure
was wondering if maybe you like to cook up a UPS FAQ with some juicy linkage?

I'm more inclined to write a "good power supply" FAQ, describing how a power supply works and how to identify if a power supply is a piece of shit or not by pulling the lid.

But heck, I'll write a quick UPS FAQ if wanted. Give me a while though; I'd like to bring a scope home from work and get some pictures of waveforms from my BackUPS.

 

[qdemn7]

I'm more inclined to write a "good power supply" FAQ, describing how a power supply works and how to identify if a power supply is a piece of shit or not by pulling the lid.

But heck, I'll write a quick UPS FAQ if wanted. Give me a while though; I'd like to bring a scope home from work and get some pictures of waveforms from my BackUPS.

Yes please to both.

 

[jasonlitka]

very few UPSes put out stepped sine waves; most non-sine UPSes (eg, APC BackUPS units) put out a filtered square wave which is more like a "fatter" sine wave. And switching power supplies actually *prefer* this non-sine waveform over a true sine wave. The non-sine waveforms reduce the ripple current in the input capacitors and input rectifier.

PFC circuits won't care what you give them, as long as it's not a pure square wave or anything.

Oh, and this is coming from someone who designs power supplies as part of his day job...

That's not what APC says. My info came straight from them. They said that their cheap units were better than everyone else's because they used a stepped sine wave where as everyone else used a square wave. Their SmartUPS line uses a true sine wave. I had problems with one of their BackUPS models along with a PCP&C PSU. Replacing it with another BackUPS didn't help so they sent out a SmartUPS as a replacement. It worked fine. Some PSUs DO prefer a true sine wave over a stepped one or a square wave.

 

[Bitchnmoan]

I'm more inclined to write a "good power supply" FAQ, describing how a power supply works and how to identify if a power supply is a piece of shit or not by pulling the lid.

But heck, I'll write a quick UPS FAQ if wanted. Give me a while though; I'd like to bring a scope home from work and get some pictures of waveforms from my BackUPS.

Attn: Ice Czar - when it comes out, slap some glue on the back and make it a sticky






...just a suggestion from the peanut gallery

 

[FLECOM]

That's not what APC says. My info came straight from them. They said that their cheap units were better than everyone else's because they used a stepped sine wave where as everyone else used a square wave. Their SmartUPS line uses a true sine wave. I had problems with one of their BackUPS models along with a PCP&C PSU. Replacing it with another BackUPS didn't help so they sent out a SmartUPS as a replacement. It worked fine. Some PSUs DO prefer a true sine wave over a stepped one or a square wave.

APC Smart UPS > *

i have like 6 of them in my house...

miami power = teh suck

 

[Ice Czar]

I'm more inclined to write a "good power supply" FAQ, describing how a power supply works and how to identify if a power supply is a piece of shit or not by pulling the lid.

But heck, I'll write a quick UPS FAQ if wanted. Give me a while though; I'd like to bring a scope home from work and get some pictures of waveforms from my BackUPS.

Both, and yes glue would be liberally applied

 

[gee]

Both, and yes glue would be liberally applied

I lack free time, so this might take a while.

I also don't have many "reference" PSUs around to compare; it'll be an "evolving" FAQ, I think.