Jimmy wrote:
Hi Paul,
I'm not skilled about IT and I thought my PSU max power consumption was enough to establish UPS max power supplying for my PC, anyway that's my hw cfg (but PSU of course):
- CPU amd ryzen 2200g = cTDP 46-65W
- mobo msi b450-a pro = honestly I don't know!
- ram HyperX Predator DDR4 HX432C16PB3K2/8 Kit 8 GB (2 x 4 GB), 3200 MHz, DDR4 CL16 DIMM = I don't know exactly but I guess about 2x1.5W = about 3W
- hdd WD black @7400rpm (WD1003FZEX-00K3CA0) = 6.8W (read/write)
- monitor Acer x193w = 37W
- other stuff: basic mouse + basic keyboard + case (Sharkoon S25-w with 2 fans) = I guess just a couple of Ws
TOTAL = 111.8W for sure + mobo + other stuff = I guess it's all under 200W
Now the bad news: here in Europe I can't buy neither APC BR1000MS nor CyberPower CP1350PFCLCD series nor GX1325U series. I'm especially sorry for APC which I know is an UPS market leader. Here I can buy these cyberpower UPSs
https://www.cyberpower.com/eu/en/pro...inewave#models
in particular I pointed my attention to cp900epfclcd 900VA pure sine wave model:
https://www.cyberpower.com/eu/en/pro...u/cp900epfclcd
which is my "milestone" both for specs and price. I can buy it for 170eur so let's put my budget to 206USD just to give an international gauge 
There's also this Powerwalker, which is a very cheap alternative UPS with pure sine wave I can get here for just 85eur:
https://powerwalker.com/?page=select&cat=VI_SW&lang=en
and the closest to the above cyperpower is
https://powerwalker.com/?page=produc...120080&lang=en
800 VA - 480W (Output Power Factor 0.60) - Line-Interactive - Active PFC - Pure Sine Wave
I'm a bit skeptical about the "pure" sine wave declared due to its low cost, I can just point your attention to these amazon buyers' reviews:
- https://www.amazon.de/-/en/gp/custom...SIN=B00K792UR0
- https://www.amazon.it/gp/customer-re...SIN=B00K792UR0
but we have to trust! If those graphs are genuine then I guess its components are very cheap (and weak?); that's my only explanation for a so low priced pure sine wave UPS. Anyway what do you think of this "kind" of sine wave shape? Will it fry my active PFC UPS when on battery mode?
I'm just afraid the powerwalker won't last very much, I don't mean its battery but its electronics. By the way, are they comparable (lasting/cost) by a long time period "investment calculus"? In other words will the cyberpower last the double (or more) than the powerwalker? Finally consider I've got a welder and I can make very "easy" fixes like changing capacitors so I'll take a "little" electronic cure by myself of my 200$ investment
The Powerwalker sure has lots of specs, but it's pretty
difficult for me to judge whether it's better or worse
than others, because the others don't give that level
of spec.
Units with continuous fan operation, that's usually an indication
of the double-conversion type of UPS. It has zero switching time.
And the Powerwalker has some relatively good numbers. It only has
one state transition which is similar to SPS UPS (that's the kind
of old-fashioned UPS I've got). On an SPS, it basically needs
a cycle to recognize it needs to make a transition. Whereas the
double conversion ones, the inverter portion is always running
and so the heat output from the unit in that case, is
proportional to load. On an SPS (where the inverter only runs
on battery), those tend to be "stone cold" and you don't
feel any heat. I don't think I've even felt heat while it
was running on battery, but there really should be some.
There is more than one way to make sinewave output. Some
units are ferroresonant, and they use a big coil or transformer
as part of their "smoothing" process. In those cases,
perhaps the drive isn't a sinewave, and additional magnetics
are used to coerce the output. The other way to make
a sinewave, is to do a PWM classD amplifier, which means
the output stage might run at 100KHz to 1MHz and the pulsewidth
of the switching stage is used to "draw" a sinewave. Such a circuit
still needs filtering on the output (a low pass reconstruction filter).
On the load side, you have several load types.
Light bulb = easy to drive, takes anything, a square wave or DC would work
SMPS with no PFC = shouldn't have a problem with stepped sine.
Only the front end filter components which try to stop
noise onto mains, they might buzz a bit in bad cases,
like say square wave drive on a camping trip.
SMPS with active PFC = may not be happy with stepped sine.
Sinewave can have harmonic content without
killing the thing. Non-first-generation
SMPS seem more tolerant. The Italian scope
picture should not be a problem.
Turntable motor, transformers (AV receiver shielded transformer) =
They expect low harmonic input, third or fifth
harmonic of mains frequency. Hard to judge by
eye on an oscilloscope, exactly how bad the
harmonic level is. Could be verified in
Audacity (FFT display) in a crude fashion.
I have some transformers plugged into my SPS UPS with stepped sine
output, and haven't noticed any buzzing noises.
The reason the active PFC was freaking out, was the "discipline" used.
The purpose of active PFC, is to try to get the mains current waveform
to be "in-phase" with the voltage waveform. So what the designers
said was "hey, since the mains is such a nice sine wave, let us tell
the PFC circuit, to coerce the current waveform to follow the voltage
waveform". This is great on mains, and works no problem. But now,
we consider the case of powering our equipment with an auto battery
to square wave drive mains device (used on camping trips). With
the square wave output, the PFC circuit says "yikes, I must make
a square wave current waveform". Which is unnatural, and forcing those
currents through front end filters makes for audible noise effects.
If the waveform on battery is stepped sine, that has a fair amount
of harmonic content, and the forced current waveform inside the active
PFC circuit of an ATX supply, is still not that good.
Any sort of sine-like waveform, without evidence of steps, is
"good enough" protection from causing the most observable effects.
Even if the sine wave isn't "pure", it's likely good enough to pass.
The harmonic limits on transformers, the allowance there is lower.
I can't imagine a turntable motor being all that happy running
on a mains "square wave" type of output.
In the computer world, they like to make things undetectable to
humans, by pushing the frequencies involved above 25KHz or so.
So that you can't hear that some circuit is "tortured". But with
mains power, if electrical components are "unhappy", the 50Hz or
60Hz (or third or fifth acoustic harmonics) are quite audible.
*******
If the runtime on the Cyberpower is good enough for you (7 minutes
with your PC running full blast), maybe that's good enough for the
job. But it's a false economy, to be buying a UPS close to the
limits of the load, then go home and say "you know, I really should
plug X, Y, and Z items into this thing too". You want a little bit
of margin.
When I check the numbers on the side of the UPS box here, I'm
probably (worst case) now, at the limit. But the newer PC only
goes to full power, on synthetic tests (Furmark + Prime95), and
I don't have an excuse to be running Furmark for more than a
minute or so. I don't tend to do fancy thermal testing on that
PC. Quite often, the CPU itself is railed at 156W doing 7ZIP,
but the UPS is sufficient for that operating condition. I don't game
on the machine, so the video card might do things like
video encoding or decoding (60W of 180W max).
I don't know what to tell you about the Powerwalker. I would
be reading the customer reviews, for any reports of damage or
acoustic effects. I mean, when Cyberpower first came out,
they were a bit on the flaky side. I don't really know how
long those companies have been around.
The double-conversion units (the type we used at work), those
used to start at around $1000 or so. And they kick off heat
and aren't 100% efficient even on mains. But they do work.
They're trusted by IT people, for things like tape backup
systems and the server room.
I've not had any trouble with my stepped sine SPS UPS, but
then I also haven't been teasing it with active PFC power
supplies. I do have an 80+ ATX supply here I could test
with, but the machine that is in, is seldom used. The two
machines normally running, are not PFC corrected.
Summary: Cyberpower may be good enough.
Powerwalker, needs more customer reviews to get some
idea whether they have fallout or QA problems. Even APC
designs can have problems - this is mains power and it
ruins stuff :-) Even if I was buying an APC, I'd be
reading the reviews to see if they've slipped in
the quality department.
Every company has a "lowest tier" UPS in the $50 range.
And those will be a test of their "minimum quality"
standards. That's where you find out what happens when
they don't test the products at the factory. For example,
at the last company I worked for, we bought around 100+
UPS for employee cubicles, and roughly 10% would either
not switch to battery, or would not switch back to mains
when mains came back. Just to give some idea what untested
rubbish looks like. Those 10% would have to go back. Those
were also more expensive than $50 each.
Paul