a buzzing sound from the SMPS when pc runs on Back-up UPS

[nix253]

hey guys i just bought a new APC Back-UPS RS 1500 (BR-1500-IN) which also happens to be my first APC product and i really like the features especially the auto-shutdown software and other software-supported monitoring.

but the issues is that whenever i run SELF-TEST from powerchute personal edition or if i switch off the main AC supply (just like in case of power outage) and the PC runs on battery back-up then there's a strange "buzzing" sound that comes from my PSU/SMPS. had the sound been feeble i wouldn't have cared much but sound is quite loud, if not extremely loud.

so what do you guys think could be the reason n how much chances are there that it could harm my pc in some way or the other n upto what extent?

also the power outage in the area where i live isn't too frequent but still every once in a while it is there.

n the settings that i've changed in the powerchute software is
Sensitivity-High and Runtime on Preserve battery option with computer to be shut-down after 1 minute.

the specs are as shown in sig. with display being connected separately and not on the UPS.

 

[Emulex]

Yeah you need to replace it with a pure sine wave backup. You have a low end modified square wave model

the SUA or SMT line is good.

The cyberpower puresine is good.

I just ran into this problem again with a 94% energystar box . the machine would crash and wouldn't boot (memory error beeps) when on the BACK-UPS [when running off battery] (cheap standby modified square wave) - plugged it direct to surge = no problems.

put a SUA1500RM2u - no problems.

back to BACK-UPS (modified sine wave) - FAIL FAIL FAIL.



Gotta remember that these new energy star ACTIVE PFC will freak out (Sometimes) on cheap square wave. Gotta use the good power. Cyberpower has really nice pure sine wave units 800va if you can't afford an SUA or SMT APC line.


machine in question was DC7900 hp - 94% HE platinum power supply with ACTIVE PFC.

we had deployed 100+ of similar HP's ( i forgot) and 50% of them would not run on battery power at all (reject) 50% would flake when running on battery - all had to have the back-ups replaced with cyberpower PURESINE units - ever since then 100% satisfaction.

 

[SparkyJJO]

Issues with the modified or approximation sine aren't consistent. The buzzing is guaranteed, but other than that, it's a hit or miss whether it will be a problem or not.

My Corsair buzzes like the rest, but it doesn't affect its function when on battery. And battery is only for a few minutes anyway.

If your PC runs fine when the UPS is on battery mode aside from the typical buzz, then you're fine and I wouldn't worry about it. If it has issues running, then you would need to cough up the extra bucks for a pure sine output UPS. Of course, if the buzzing is too annoying then the pure sine would fix that, then again its only for a few minutes anyway so whether or not it is worth the extra for the quiet is up to you.

 

[Emulex]

I'd suggest you run a video benchmark and prime95 while on battery to see if it is stable. trust me on that one. if you can run 10 minutes balls out no errors - probably good to go. if not you got problems.

 

[nix253]

actually since that buzzing is little too bothering for me so i've set the power chute software to shut the pc down after it's been on the battery for 1 minute..... n usually this is helpful when i'm not immediately around.... if i'm or when i'm back to my pc i shut down everything else too including the UPS.

i mean there won't be a case where i'll let the the PC run on UPS battery with the buzzing for more than 3-4 minutes... so now with that point in consideration do you guys think it'll be ok if i keep this 'stepped sine wave' one?

actually where i stay it's hard to get things replaced even if in warranty .....so....

 

[Emulex]

just don't expect reliability on battery power. it's a crapshoot. do your testing and see. run memtest or some big game for a minute or two on battery and see if it craters.

 

[Modelworks]

A square wave UPS really shouldn't be causing problems for a properly designed PFC supply. The output of a PFC circuit is after all a square wave. I suspect those supplies that are having issues are ones that didn't build enough room for error in the switching circuit on the primary stage. Some big name supplies are really bad about needing a pure sine wave because the engineers didn't consider anything but optimum conditions with clean power.


The UPS supplies that are not pure sine wave are not really square wave, they are modified sine wave. Sort of like a sine wave with flat peaks.

 

[Emulex]

the modified square wave is sorta the problem. the other problem is the demand load increases which then squashes the squarewave more towards its original shape _ - _ - then the p/s demands more power and it deforms even further. in some cases due to lack of current limiting the ups can just shutdown (or not). it happens very fast but it's a vicious cycle.

and the degree to which it can occur is unknown. maybe avoid active PFC and stick with passive PFC

 

[bigboxes]

Yeah, I just went through a UPS upgrade. I got my wife the BR1000G (APC 1000VA) because she has an older machine with a Antec True550. I bought a CP1500PFCLCD (Cyberpower 1500VA, they are much cheaper than APC's pure sine) as I have a Seasonic 850 which as active PFC and I just didn't want to chance stability.

 

[njdevilsfan87]

My 450VX buzzes when my UPS turns on. My 850HX on the other hand doesn't.

 

[Mark R]

The UPS supplies that are not pure sine wave are not really square wave, they are modified sine wave. Sort of like a sine wave with flat peaks.

They're not at all curved, and they have more resemblance to square waves than sine waves.

The waveform looks kind of like this:

  -     -     -
-- -- -- -- --
     -     -

There are short sharp rectangular pulses alternately between positive and negative, with long gaps in between. To compensate for the short pulses with large gaps, the pulses are often of very high voltage, usually around 200 V/400 V (whereas a normal AC sine wave peaks out at 170 V/340V).

This doesn't matter for non-PFC power supplies, as the net effect is extremely similar to how those supplies operate anyway.

Typical current waveform from a non-PFC PSU. This shape waveform is quite similar to the voltage waveform from a modified square/sine wave PSU, with the exception that the voltage waveform is squarer.

pPFC systems shouldn't have a problem with the modified voltage waveform, but may make a noise.

aPFC systems may also work as long as the waveform isn't egregious. aPFC systems work by matching the current to the voltage waveform - they will shutdown during zero voltage periods, and draw high current at high-voltage periods. The major issue that aPFC systems have with modified square wave inverters is the abrupt change in voltage, which may be too fast for the current control system to respond adequately. This is usually because the PSU designer was lazy and slowed the control system down in order to make it more stable, instead of properly analysing it and tuning it.

 

[Emulex]

low end battery backups also do not have current limiting - they only shutdown. and the switching time seems longer for low end models than say a pure-sine standby.

 

[neo350]

Dude better replace the ups asap it is my second cooler master GX. It is one hefty problem, after sometime ( about an year ) If you run your pc on ups backup frequently your psu will fail for sure. the problem will be sudden turn off of the whole pc, and gradually death of psu it will be quick after it shows the first symptom. it will take a long time to replace a new one from cm but they have good customer support. better safe than sorry...

 

[nix253]

ok guys today i tried something n this is what i found out... till yesterday i had my pc, modem and speakers connected to a belkin power surge protector which was actually connected to the UPS. but today i thought of trying out connecting my pc directly on ups and see if humming goes out. well when i did the humming didn't go out totally but it was significantly reduced. so i'm thinking of keeping my pc directly to the UPS.

the only concern i'm having is that my pc may not get the extra protection which it was getting through the surge protector. so is the surge protector necessary or it's ok to use my pc directly on UPS? i think UPS also provides protection from surges upto a certain extent don't they?

here's the page on the surge protector:
http://www.belkin.com/in/IWCatProductPage.process?Product_Id=481734