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Good and affordable UPS for Corsair CX450



 
 
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  #1  
Old December 8th 20, 11:24 AM posted to alt.comp.hardware
Jimmy[_7_]
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Posts: 3
Default Good and affordable UPS for Corsair CX450

I've built a "basic" PC desktop, I mean 150-200w max for "basic" including my monitor, with a Corsair CX450 PSU (OEM CWT RPS0053) with active PFC. Now I need a UPS but my budget isn't high to get the best (eg. an online UPS) so I'd like to buy a UPS with the best quality/price relationship for my goals and equipment within 180USD. AFAIK I need a UPS that generates a pure sine wave during a blackout because of my PSU's active PFC, now let's define my goals.

My worst scenario is when it's raining hard because blackouts occurs randomly, eg. last time it rained there were 3 blackouts within 30 minutes and then no more ones though it kept on raining for hours. My "limit" is 2 close blackouts, I mean I've to be able to shut my pc off correctly during the 2nd blackout then... I'll just wait for better weather time Well my electrical system suffers brownouts oftenly too but I guess a line-interactive UPS, I mean with AVR, will be a solution for that.

That said please tell me how much minimum power (VA / W) has to generate an UPS to get my goal, I mean the worst scenario I've described above. Then please tell me if an UPS must have other specifications. Finally please suggest me some UPS models to buy within 180USD that fit my personal case.
  #2  
Old December 9th 20, 05:28 AM posted to alt.comp.hardware
Paul[_28_]
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Posts: 1,467
Default Good and affordable UPS for Corsair CX450

Jimmy wrote:
I've built a "basic" PC desktop, I mean 150-200w max for "basic" including
my monitor, with a Corsair CX450 PSU (OEM CWT RPS0053) with active PFC. Now
I need a UPS but my budget isn't high to get the best (eg. an online UPS) so
I'd like to buy a UPS with the best quality/price relationship for my goals
and equipment within 180USD. AFAIK I need a UPS that generates a pure
sine wave during a blackout because of my PSU's active PFC, now let's define
my goals.

My worst scenario is when it's raining hard because blackouts occurs randomly,
eg. last time it rained there were 3 blackouts within 30 minutes and then no
more ones though it kept on raining for hours. My "limit" is 2 close blackouts,
I mean I've to be able to shut my pc off correctly during the 2nd blackout
then... I'll just wait for better weather time Well my electrical system
suffers brownouts oftenly too but I guess a line-interactive UPS, I mean with
AVR, will be a solution for that.

That said please tell me how much minimum power (VA / W) has to generate an
UPS to get my goal, I mean the worst scenario I've described above. Then please
tell me if an UPS must have other specifications. Finally please suggest me
some UPS models to buy within 180USD that fit my personal case.


If you put the computer and monitor on a single outlet strip,
then plug it into a Kill-O-Watt meter, you can get both a W and a VA
measure at the touch of a button. You run Furmark and Prime95 on the
computer, to max the power demand, then take a reading. This gives
you an accurate value fo total W and total VA. For an active PFC device,
you expect the W = VA since PF ~= 0.99, but the meter leaves nothing
to the imagination. The LCD monitor is unlikely to be PF 0.99, and would
be a tiny contribution of PF = 0.65 loading.

https://www.amazon.com/P3-P4400-Elec.../dp/B00009MDBU

On modern Intel processors, they can turbo above TDP, so TDP isn't
necessarily a complete characterization. Just a word of warning not
to "shave it too close".

There is also the possibility of buying a "really cheesy" UPS,
one where it doesn't deliver the rated power, and to get
some runtime, there's a good chance your capacity (max Watts expected)
will be covered anyway.

Since you didn't give any indication of what's in the PC,
it's hard to give ballpark numbers. I can illustrate with
my PC here.

Video card manuf rated 180W draws 180W (modern cards use a power limiter)
CPU manuf rated 130W draws 156W (ATX12V inefficiency is the difference)
My CPU has turbo turned off
Motherboard allocate 50W
HDD look it up 8W to 15W HDD, 2.5W SSD

Total 375W

My monitor might be 35W or so, because it's tiny by modern
standards. The new machine got a $100 monitor, because the
hardware for the basic computer cost so much ($800 worth of RAM).
RAM sticks are around 1W apiece (standby value). I would
bundle the RAM loading, into the motherboard number. Exceptions
for monstrous server devices with FBDIMM, where the loading
is significant.

So now we're at 410W, and we have a budget of $180 USD.

*******

APC BR1000MS 1000 VA Pure SineWave 10 Outlets 2 USB Charging Ports Back-UPS $147

https://www.newegg.com/apc-br1000ms-...82E16842301698
https://www.apcguard.com/BR1000MS.asp

1000 VA / 600 Watts
Battery Type Sealed Lead Acid
Battery Run Time 600W: 3.7 minutes
400W: 8.0 minutes
200W: 20.5 minutes
Replacement Battery APCRBC160
RBC Quantity 2
Expected Battery Life (years) 3 - 5

Topology Line Interactive
Waveform type Sine wave
Boost AVR: Correcting low voltages without discharging the battery.

Net Weight 22.49lbs. (10.2KG)

They're careful to not give any ratings on the battery pair
https://www.apc.com/shop/us/en/produ...60/P-APCRBC160

CyberPower CP1350PFCLCD 1350 VA / 810 Watts PFC Pure Sine $199
Weight 20.30 lbs.

CyberPower GX1325U 1325 VA 810 Watts 10 Outlets UPS, Pure Sine $180
Weight 20.30 lbs

CyberPower CP1000PFCLCD UPS 1000 VA / 600 Watts PFC compatible Pure Sine $155
Weight 15.90 lbs.

Pick the middle one.

CyberPower GX1325U 1325 VA 810 Watts 10 Outlets UPS, Pure Sine $180

https://www.newegg.com/cyberpower-gx...82E16842102238
https://www.cyberpowersystems.com/pr...ackup/gx1325u/

1325 VA / 810 Watts
Battery Type Sealed Lead Acid
Battery Run Time 600W: 5 minutes
400W: 9 minutes
200W: 22 minutes
Battery Quantity 2
Battery Size 12V 7Ah (for 2-pak?)
Battery Type SLA
Replacement Battery Cartridge RB1270X2A ($70USD for 2-pak)

Topology Line Interactive
Energy Saving GreenPower UPS Bypass (means similar to SPS, no constant fan)
Waveform type Sine wave
AVR Single Boost

EMI/RFI Filtration Yes
Phone / Network Protection RJ11/RJ45 1-In / 1-Out (Combo)
Surge Suppression (Joules) 1030 J

Weight 20.30 lbs

The feature set on these units, is pretty similar. You
might want to compare the connectors on them. The APC has a
crazy data port (looks like an RJ series), which comes with
an adapter cable with some sort of USB on the other end. Both
units have supervisor cables, and these cables ("data port")
allows software on the PC, to do a clean shutdown of the
PC when the battery is partially drained.

I picked the middle one to try to get more runtime. But
they're really within spitting distance.

Notice also, that the word "sinewave" is treated in a cavalier
manner. They like to combine "sinewave" with "won't cook active PFC
goods", which with modern equipment, might still be met with a
stepped sine waveform. You need stronger language such as
"Pure Sine" to signify something a power company would be
sending to you as a waveform. It's always possible,
to meet a price point, these are stepped sine units.

But that'll give you some idea what is available at your
price point. These are not bottom tier UPS. $50 buys you
the "will stay up for a second if the lights blink" UPS.

Read the reviews to see how many catastrophic failures
the designs have had. The warranty on these units, is
generally "catch me in court, dummy" material. The companies
will generally be non-responsive if you claim their unit
smoked your gear. At a bare minimum, *make sure* to plug
these piles of crap directly into the wall. One
of their favorite warranty denials is "you used an extension
cord". The units must be fed from robust wall sockets.

Paul
  #3  
Old December 9th 20, 04:50 PM posted to alt.comp.hardware
Jimmy[_7_]
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Posts: 3
Default Good and affordable UPS for Corsair CX450

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
  #4  
Old December 9th 20, 07:54 PM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default Good and affordable UPS for Corsair CX450

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
  #5  
Old December 13th 20, 08:50 PM posted to alt.comp.hardware
Jimmy[_7_]
external usenet poster
 
Posts: 3
Default Good and affordable UPS for Corsair CX450

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.
Did you already read the cyberpower cp900epfclcd datasheet here?
https://www.cyberpower.com/eu/en/Fil...DS-18080023-01

By the way, I amazon-ed a little bit to search an USA cp900epfclcd's "brother" and found the cpXXXpfclcd "family". As you can see the "e" is missed and I guess it stays for european (?). If yes, in the sense if there're no other important differences, consider this
https://www.amazon.com/CyberPower-CP...dp/B00429N18S/
You can find infos he
https://www.cyberpowersystems.com/pr...e/cp850pfclcd/
and its datasheet here
https://dl4jz3rbrsfum.cloudfront.net...P850PFCLCD.pdf
The first difference I read is about the on-battery wave output: just "sine wave" and not "pure sine wave" as the EU family (cpXXXEpfclcd) BUT if we look at amazon buyers' comments, we can get these graphs:
-CP1500PFCLCD
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
-CP1350PFCLCD
https://www.amazon.com/gp/customer-r...SIN=B00429N19M
We'd trust as usual. Unfortunately there's nothing similar for the 850VA model within comments. My only concern is I guess there could be a certain possibility cyberpower built the "upper class" models (eg. 1500VA) with a better electronics than the "lower class" ones as the 850VA. I say that because AFAIK certain brands do this job: different models quality within the same models "family" (eg. a laptop series); what do you think about this cyberpower case?

I share your same doubts about the powerwalkers because for now it's hard to find many feedbacks to "study". Just this 800VA model
https://www.amazon.it/BlueWalker-Pow.../dp/B00K791C1U
has 101 ratings and they're "quite good". My "favorite" comment is
https://www.amazon.it/gp/customer-re...SIN=B00K791C1U
and tells the main problem is the transformer is not cool down enough by the heatsinks so the UPS won't last so much.

By the way, there's also the PSW powerwalker series
https://powerwalker.com/?page=select&cat=VI_PSW&lang=en
and it's more exspensive than the SW series I wrote above. Honestly I don't understand the differences, can you help me? Let's consider the 750VA model
https://powerwalker.com/?page=produc...120081&lang=en
with its datasheet
https://powerwalker.com/datasheets/P...SW%20Promo.pdf
I don't think the difference SW / PSW is just "sine wave" / "pure sine wave" because the SW generates pure sine waves too, so what's different to the SW series brothers?
  #6  
Old December 14th 20, 05:57 AM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default Good and affordable UPS for Corsair CX450

Jimmy wrote:
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.

Did you already read the cyberpower cp900epfclcd datasheet here?
https://www.cyberpower.com/eu/en/Fil...DS-18080023-01

By the way, I amazon-ed a little bit to search an USA cp900epfclcd's "brother" and found the cpXXXpfclcd "family". As you can see the "e" is missed and I guess it stays for european (?). If yes, in the sense if there're no other important differences, consider this
https://www.amazon.com/CyberPower-CP...dp/B00429N18S/
You can find infos he
https://www.cyberpowersystems.com/pr...e/cp850pfclcd/
and its datasheet here
https://dl4jz3rbrsfum.cloudfront.net...P850PFCLCD.pdf
The first difference I read is about the on-battery wave output: just "sine wave" and not "pure sine wave" as the EU family (cpXXXEpfclcd) BUT if we look at amazon buyers' comments, we can get these graphs:
-CP1500PFCLCD
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
https://www.amazon.com/gp/customer-r...SIN=B00429N19W
-CP1350PFCLCD
https://www.amazon.com/gp/customer-r...SIN=B00429N19M
We'd trust as usual. Unfortunately there's nothing similar for the 850VA model within comments. My only concern is I guess there could be a certain possibility cyberpower built the "upper class" models (eg. 1500VA) with a better electronics than the "lower class" ones as the 850VA. I say that because AFAIK certain brands do this job: different models quality within the same models "family" (eg. a laptop series); what do you think about this cyberpower case?

I share your same doubts about the powerwalkers because for now it's hard to find many feedbacks to "study". Just this 800VA model
https://www.amazon.it/BlueWalker-Pow.../dp/B00K791C1U
has 101 ratings and they're "quite good". My "favorite" comment is
https://www.amazon.it/gp/customer-re...SIN=B00K791C1U
and tells the main problem is the transformer is not cool down enough by the heatsinks so the UPS won't last so much.

By the way, there's also the PSW powerwalker series
https://powerwalker.com/?page=select&cat=VI_PSW&lang=en
and it's more exspensive than the SW series I wrote above. Honestly I don't understand the differences, can you help me? Let's consider the 750VA model
https://powerwalker.com/?page=produc...120081&lang=en
with its datasheet
https://powerwalker.com/datasheets/P...SW%20Promo.pdf
I don't think the difference SW / PSW is just "sine wave" / "pure sine wave" because the SW generates pure sine waves too, so what's different to the SW series brothers?


The one that claims "PWM" and "98% efficiency" would
be a class D digital one which "draws the waveform with narrow
square waves", then follows that with a low pass filter to
only pass the fundamental. (At least, that's the one principle
I can imagine doing this.) The low pass filter is in effect
the regeneration filter. Because it's PWM, the transistors
in the output stage are either open (OFF), or saturated ON, which
is where the "digital" terminology comes from. Saturated transistors
dissipate little heat, and then it's the regeneration filter
that's the only questionable part of the design (how is it
done, does it generate heat). The 98% efficiency, that tells
you how many watts the inside of the box dissipates. Not much heat.

They also make stereo equipment that way. Class D with filter.

As for the one that has the overly hot transformer in it, it
could be a ferroresonant design. The heat could be a sign of
eddy currents and harmonic content being driven into it. I don't
know the operating principle well enough for ferroresonant,
to say more about it. Generally, if a design is not efficient
and is kicking off heat like that, that's the kind of
design that needs "constant fan" for as long as the heat
is present. If the users find it hot with the cover off (where
at least it gets convection cooling), it's going to be much much
worse with the cover on.

You can see in the oscilloscope waveform with the glitches in it,
that's some sort of crossover distortion. But it might not be
exactly the same as you'd see in stereo equipment. That glitch
would represent a bit of harmonic content, which generally would
not be too bad for an ATX active PFC load, but I suppose would
make an inductive load absorb some of that. You might just
barely be able to hear that in an absolutely quiet room,
with say a turntable motor as the load. The UPS itself
might make more noise than the turntable motor though.
Strictly speaking, that waveform is not "Pure Sine", which
implies certain operating principles, it's just a non-sine
source that is a better approximation than Stepped Sine.
That's why you'd call the output "Sine Wave" output, because
it's not quite as good as Pure Sine. It's a good enough
sine wave, a cost conscious compromise. With Pure Sine, the
method used (whatever it happens to be) is inherently glitch free.

Pure sine, used to start at $1000 or so. Any price movement
we see there today, is the evolution of the concept. The
method used in the old pure sine, might not be the same as
the ones we see today. That's because Class D only became
a fetish in more recent times. There are some 500W computer
speakers that are Class D, but two stage Class D, with one
stage being a kind of programmable power supply, the second
stage drawing the final waveform, with little thermal overhead.
The drop across the final transistors is only a few volts at most.

Paul
 




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