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Author Topic: A Silent UPS  (Read 939 times)

jack21

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A Silent UPS
« on: July 04, 2019, 05:30:54 PM »

I thought this may be of interest to anyone desirous of a silent UPS.

I've posted a few years ago how I cobbled together a 12v DC mini UPS set-up which has now been in continuous use powering my modem/router(s) and RPi. It has, and still, performed flawlessly, and tho it only has a 7Ah battery it has saved the day on many occasions - over 12 hours in one instance. It is truly silent. When a powercut occurs, I can use an old laptop to access the RPi which runs DSLstats, or to access the modem/router.

For quite a while I've hankered after something similar to protect my silent ITX-based-desktop and monitor (together they use around 40W); I had once used a Belkin 325W UPS but its humming (not on battery) disturbed my office quiet, and when it developed other issues it was sent to recycling. I considered quite a number of low-cost UPS units, but reviewers frequently grumbled about 'humming' mains-related, so the idea faded.

Just recently I came across PowerWalker UPS as an alternative to the main players, and when I found a basic 360W one online at a bargain price from The UPS Centre  I decided to give it a go....PowerWalker Support assured me it was silent. Anyway it arrived today, and sure enough it is silent when running on mains, and very quiet when on battery. I've tested its powercut operation - completely fine. And I will get round to using its USB connector for monitoring/shutdown in due course. Though it only has a 5Ah battery, that will be easily enough for my purposes.

The model I picked is the PowerWalker VI 650 SB UK from www.upscentre.co.uk and was just over £40 in total, including next-day delivery....its also available elsewhere.

Sorry; I forgot to add a link to its datasheet.....https://powerwalker.com/?page=product&item=10121096
« Last Edit: July 05, 2019, 05:04:11 AM by jack21 »
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burakkucat

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Re: A Silent UPS
« Reply #1 on: July 05, 2019, 12:00:42 AM »

Thank you for those details. I believe this is the link to the model that you purchased.
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Weaver

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Re: A Silent UPS
« Reply #2 on: July 05, 2019, 03:42:02 AM »

Thank you for this link. Interesting.

Btw any idea what they might mean by Ďmodified sine waveí ? I have seen mentions of similar terms before but I forget what horrors might lie therein. I presume the English word Ďmodifiedí is in this case equivalent to the words Ďnot (remotely) aí.
« Last Edit: July 05, 2019, 04:07:46 AM by Weaver »
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jack21

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Re: A Silent UPS
« Reply #3 on: July 05, 2019, 05:21:36 AM »

Hi Weaver,

Here's a reasonable explanation - https://www.altestore.com/blog/2015/10/pure-sine-wave-vs-modified-sine-wave-whats-the-difference/#.XR7NFoKNbOw

Many UPS don't produce a pure sinewave, those that do usually cost more, but the issue has never affected me so far.....modem/routers, desktops, monitors, laptops have all been fine.
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jack21

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Re: A Silent UPS
« Reply #4 on: July 05, 2019, 06:18:14 AM »

@Burakkucat

Thanks for adding the link....but it isn't exactly the one I bought, which now appears to be superceded by the newer model referenced in your link. However there is still a cheaper, basic, but with IEC socket output one here: https://upscentre.co.uk/onlinestore/product/powerwalker-vi-650-va-360-watt-iec-ups/

The model I purchased, PowerWalker Basic VI 650 SB UK  is still available via (say) CCL Computers, eBay etc.
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Weaver

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Re: A Silent UPS
« Reply #5 on: July 05, 2019, 06:28:55 AM »

@jack21 - yes I have read about non-sinusoidal output devices a long time ago, but I forget now, that link is very useful. I see that that shop makes a feature about well-behaved close-to-sinusoids output on some of their devices, so itís there if you want it. The reason that Iím interested is that Iím wondering about the effect of the high order harmonics on the modems.

We have discussed this before in earlier threads, but memory once again fails me completely. But I have a vague recollection of having been warned about this before, perhaps on account of the isolation effect of a modemís own internal first-line components or what happens in a cheap DC PSU - I just donít know now. Even with my usual level of paranoia and ignorance concerning this matter, it may be that this is a non-issue. I would in any event be putting the mains through an Belkin anti-surge+filtering device - from the top of their range - between ups and modems and the Belkin device has mains filtering intended for audio-video equipment. If that works at all then it might get rid of any spurious noise output from the ups anyway. So if that does its job then who cares. But it may be that there are quite low order  harmonics too, or very loud high order harmonics - who knows what - but anyway stuff that the Belkin is not designed or intended to handle. (There is another anti-surge unit on the mains-side/wallsocket-side of the ups too to act as a first line of defence against lightning and EPR/GPR, and this should protect the ups too.)
This could be tested by carefully looking at the stats from the modems.
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jack21

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Re: A Silent UPS
« Reply #6 on: July 05, 2019, 06:51:11 AM »

@Weaver

I believe that a line-interactive (as opposed to in-line or double-conversion) UPS does not, in ordinary non-powerfail operation, alter the sine wave inherent from mains supply, and that it is only in mains-failure operation that the output via inverter becomes modified sine wave. I've read as such on manufacturer's website - but I don't have an oscilloscope to definitively check it.

I imagine that switching power supplies might not do as well when powered via the inverter, but I have to say that any I tried still functioned apparently OK, and I recall that even an ADSL modem powered by a switching wall-wart via a modified sine wave UPS was apparently unaffected in any performance way when I simulated a power failure (those tests were done some years ago using a cheap Belkin UPS).
« Last Edit: July 05, 2019, 07:19:41 AM by jack21 »
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Weaver

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Re: A Silent UPS
« Reply #7 on: July 05, 2019, 06:54:06 AM »

Ah. I didnít know that. Iím learning something. Thatís why Iím here, to try and become slightly less ignorant. But with a memory like this, itís a very leaky bucket and sometimes we go backwards faster than forwards, in the educating-Weaver endeavour.
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Chrysalis

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Re: A Silent UPS
« Reply #8 on: July 05, 2019, 10:51:03 AM »

Quote
@jack21 - yes I have read about non-sinusoidal output devices a long time ago, but I forget now, that link is very useful. I see that that shop makes a feature about well-behaved close-to-sinusoids output on some of their devices, so itís there if you want it. The reason that Iím interested is that Iím wondering about the effect of the high order harmonics on the modems.

We have discussed this before in earlier threads, but memory once again fails me completely. But I have a vague recollection of having been warned about this before, perhaps on account of the isolation effect of a modemís own internal first-line components or what happens in a cheap DC PSU - I just donít know now. Even with my usual level of paranoia and ignorance concerning this matter, it may be that this is a non-issue. I would in any event be putting the mains through an Belkin anti-surge+filtering device - from the top of their range - between ups and modems and the Belkin device has mains filtering intended for audio-video equipment. If that works at all then it might get rid of any spurious noise output from the ups anyway. So if that does its job then who cares. But it may be that there are quite low order  harmonics too, or very loud high order harmonics - who knows what - but anyway stuff that the Belkin is not designed or intended to handle. (There is another anti-surge unit on the mains-side/wallsocket-side of the ups too to act as a first line of defence against lightning and EPR/GPR, and this should protect the ups too.)
This could be tested by carefully looking at the stats from the modems.

Weaver

Simulated sinewave for my kit has been fine, currently I run my main PC, 2 monitors, 2 consoles, a gigabit switch, and my pfsense firewall all through my UPS and it is simulated sinewave.  My PC has a Active PFC PSU and its still also fine.

Also many UP's clean the power feed, so will bump voltage if too low or reduce if too high, have built in surge protection as well, and generally its advisable to "not" mix surge protectors with UPS's.  So e.g. buy extension sockets that dont touch the power, no surge protection etc.

Also Line interactive if you get it, will only simulate the sinewave during an actual power outage, when power is on, there is no simulation.
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Weaver

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Re: A Silent UPS
« Reply #9 on: July 05, 2019, 11:07:10 AM »

> generally its advisable to "not" mix surge protectors with UPS's. 

Chrys, could you enlighten me a little more? Apologies if Iím just not getting it quite.
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IanG

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Re: A Silent UPS
« Reply #10 on: July 05, 2019, 11:19:33 AM »

@Weaver: Anti-surge circuitry clips input voltage peaks, but as this should happen only once in a blue moon it has no effect on normal operation or audibility.

Small power supplies commonly have an input stage of a diode bridge feeding an electrolytic capacitor, which is charged up to mains peak voltage of about 330V. The voltage decays due to the load until the next peak arrives. Input current flows only when the mains waveform is approaching a peak, and so is quite spiky, with lots of harmonics. This applies whether the mains waveform is sinusoidal or not. The current spectrum, of 100 Hz fundamental with odd harmonics, may sometimes be audible as a buzz. Harmonic currents are a problem for the supply companies, but are unlikely to affect you.

The same supply will have a high frequency switching circuit that produces a great deal of sound, mainly from magnetostriction, but by design is at a frequency above the human limit of audibility.
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j0hn

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Re: A Silent UPS
« Reply #11 on: July 05, 2019, 12:33:39 PM »

> generally its advisable to "not" mix surge protectors with UPS's. 

Chrys, could you enlighten me a little more? Apologies if Iím just not getting it quite.

From APC website.

https://www.schneider-electric.us/en/faqs/FA158852/

Quote
Schneider Electric recommends against the use of any surge protector, power strip or extension cord being plugged into the output of any APC Back-UPS and Smart-UPS products. This document will explain why.


Resolution:

Plugging a surge protector into your UPS:
The noise filtration circuitry in a Surge Protector can effectively "mask" some of the load from the UPS, causing the UPS to report a lower percentage of attached load than there actually is. This can cause a user to inadvertently overload their UPS. When the UPS switches to battery, it may be unable to support the equipment attached, causing a dropped load.

Surge protectors filter the power for surges and offer EMI/RFI filtering but do not efficiently distribute the power, meaning that some equipment may be deprived of the necessary amperage it requires to run properly  causing your attached equipment (computer, monitor, etc) to shutdown or reboot. If you need to supply additional receptacles on the output of your UPS, we recommend using Power Distribution Units (PDU's). PDUs evenly distribute the amperage among the outlets, while the UPS will filter the power and provide surge protection. PDUs use and distribute the available amperage more efficiently, allowing your equipment to receive the best available power to maintain operation.
 

Plugging your UPS into a surge protector:
In order for your UPS to get the best power available, you should plug your UPS directly into the wall receptacle. Plugging your UPS into a surge protector may cause the UPS to go to battery often when it normally should remain online. This is because other, more powerful equipment may draw necessary voltage away from the UPS which it requires to remain online. In addition, it may compromise the ground connection which the UPS needs in order to provide adequate surge protection. All APC Back-UPS and Smart-UPS products provide proper surge suppression for power lines without the need of additional protection.
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IanG

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Re: A Silent UPS
« Reply #12 on: July 05, 2019, 02:43:34 PM »

Can I stick my head above the parapet to say that much of that Schneider explanation sounds like nonsense. :o

If output spikes from a UPS are going to trigger over-voltage circuitry, I would rather change the UPS than rip out the voltage protection.
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sevenlayermuddle

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Re: A Silent UPS
« Reply #13 on: July 05, 2019, 03:55:51 PM »

On the face of it, agree with Ian G.

Added to that, most surge protectors are sacrificial, degrading a little every time a surge is caught. Thatís why some extension leads have an extra neon light, to tell you whether the surge protector is still healthy (though these lights are not reliable).

After extreme degradation, surge protectors can effectively become leaky, conducting at normal mains voltage.  At which point they might, just rarely, very very rarely, if a fuse does not blow quickly enough, combust.

In normal use, such extreme degradation is unlikely and balanced with the improbability of such a failure mode, not a major worry.   But if a PSU is producing an output that is regularly activating a surge protector, to the point they have to warn customers about the side-effects, Iíd be worried about that degradation....

https://en.m.wikipedia.org/wiki/Surge_protector
Quote
MOVs have finite life expectancy and "degrade" when exposed to a few large transients, or many small transients.[21][22]. Every time a MOV activates (shorts,) its threshold voltage reduces slightly. After many spikes the threshold voltage can reduce enough to be near the protection voltage, either mains or data. At this point the MOV conducts more and more often, heats up and finally fails. In data circuits, the data channel becomes shorted and non-functional. In a power circuit, you may get a dramatic meltdown or even a fire if not protected by a fuse of some kind.[23]
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Chrysalis

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Re: A Silent UPS
« Reply #14 on: July 06, 2019, 05:08:54 PM »

John answered the question weaver I hope his reply is good enough.
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