APC BE550G Tear-Down

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Daniel Sauvageau

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I didn't have the necessary equipment to make waveform measurements at the time but you can find the BX1000's tear-down over here: http://www.tomshardware.com/picturestory/666-ups-battery-backup-tear-down.html

It is a completely different critter, using a DC-DC step-up converter and an output bridge instead of a transformer. The old BX's iron core transformer is used exclusively for the AVR function.

I would make input power measurements if I could but the reason I got started on this streak of UPS tear-downs is because my ~10 years old BX1000 died late last year: whenever I turn it on, it clicks for several seconds and then goes to battery power. Until I get around to fixing that, whatever measurements I make may be completely bogus. I'll probably end up writing a repair story about it when I get there. I have already had a quick look inside but the obvious suspects turned out to be dead ends.

Edit: I went to measure the BX1000's standby power while 'off' (the battery charger is still active in that state) and it draws 3.8W. I would not expect the normal 'on' power to be much over 1W above that since the only "power-hungry" thing that distinguishes the 'off' and 'on' states is operating the bypass relay.
 

nukemaster

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I almost forgot you opened that unit. I wonder how close to my old XS1200 it is. Mine is warm on the side so I always guessed it was just a power waster.

I also have a very old SmartUPS 1400(got it for free and just had to add the batteries) that runs warm enough(10 - 11 degrees above room temp if I trust its software). Cools down allot when the fan kicks in(run or charge).

Again, thanks for taking the time to take these things apart.
 

Daniel Sauvageau

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It does not take much power to get things slightly warm when there is only natural convection moving heat around and limited venting directly above the heat source to let that heat out.
 

Memhorder

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Thanks again Dan. Hey have you ever done the software side of things? I know it doesn't apply to this unit but say the Cyber Power you were hinting. I've noticed that using Cyber Power panel is just not accurate when trying to figure load in real time. The bar just doesn't move when you know the computer is sucking more juice under heavy use.
 

Daniel Sauvageau

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I haven't used PowerChute or any other manufacturer software in years. I simply set Windows' power and battery management settings to bypass third-party software. If I want to read the UPS' stats, basic parameters like battery state of charge, input voltage and output power are usually readable by HWInfo and other System Management Bus (SMB) monitoring tools.
 
Don't forget to ensure a UPS is compatible with the power supply. Many need a "pure sinewave" to support Active PFC (which is required for an 80-plus rating).

Cyberpower has models with "PFC" right in the name to help avoid confusion.
 

nukemaster

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I would say as long as you keep it away from some electric motors and other devices that just do not work properly on this waveform, It should not be an issue. It is not like most users run this way long term or anything.

All of my computers have run ok on stepped wave so far(but the SmartUPS is sine). I know some active power factor power supplies(but not all) may not get along with this waveform however.
 

Daniel Sauvageau

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If an APFC power supply absolutely requires a sine wave to work correctly, then someone didn't do his job properly when designing the APFC circuit. Most APFC controllers work by approximating the RMS current necessary to maintain the main filter capacitors at a set voltage and modulating their boost duty cycle accordingly in sync with the sine wave.

In a properly designed APFC circuit, when the waveform switches to stepped approximation, the current through the PFC boost inductor rises much quicker than the controller's cycle expects due to the line voltage being 160-180V instead of the 0-170V sinusoidal progression, hits the PFC controller's per-cycle current limit and will act as a relatively constant current source until the main capacitor reaches the voltage limit.


Here's an image from my LX1500 tear-down with the green waveforms showing the expected result. There is an initial current spike due to the X-caps and APFC current limit while topping off the main capacitor, then the APFC goes constant for the remainder of the half-cycle.

Seeing that 5A spike from the plug may not look pretty but to boost line voltage from 170V to 350V at 1A, the APFC boost circuitry will be drawing more than 1A from the EMI filter and line input caps. All that ripple is not really visible from the plug simply because the EMI filter is doing its job: keeping the high frequency stuff contained within the PSU.
 

g1abhi

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I have something to ask though not related exactly to the tear down.
When APC writes 550VA or 330W , what exactly is the intended capacity of load backup. Is it able to deliver around 330W of power , or in other terms can run 5 bulbs of 50-55W simultaneously. I know about the power factor that is considered to be 60% which gives the 330W value as 60% of 550VA.
but the thing is in my country(india) APC is selling a low end 600VA ups BX-600C-IN , which is marketed as a 360W UPS, however when i run my PC with a consumption of 170W it trips totally . I have arrived at this value using the APC companion software which connected to my old APC UPS of 650VA , which can handle my PC easily .
My PC config is skylake 6500 with GTX 960 , 1 HDD , 1SSD. Seasonic SII 650W PSU. Who exactly is at fault here?
 

Daniel Sauvageau

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Yes, that's what it means. If the UPS shuts down due to overload, it either means the UPS is defective, is not meeting its specification or the load you connected to it is actually higher than you thought it was. You may need to double-check the actual power consumption using some alternate means, such as a "kill-a-watt" type plug-in power meter.


It does. Nearly all power bars also tell you not to daisy-chain them. But who follows instructions when they aren't convenient? We can pretend that the UPS plug was a small appliance instead. :)

The biggest problem with daisy-chaining is some people's lack of common sense: don't daisy-chain a dozen power bars to create a makeshift extension cord and don't run heavy loads (total) from such a contraption. I have nearly a dozen power bars around my workbench to put outlets where I want them to be but most have less than 100W worth of loads connected to them. I also have three daisy-chained power bars going around my workbench so I can switch all of my lighting and stuff I do not want to leave unattended or wasting power while I'm not there on/off with a single switch. (150W of CFL+LED light pouring out of the door is usually a blaring hint that I may have forgotten something if I get distracted after walking out.)

The other problem is some power bars' contacts getting loose over time and insert-pull cycles, especially those "flappy" ground connections: insert plugs crooked and wiggle them while unplugging a few times, the ground flaps get bent so far that they don't make reliable contact anymore. Much of the same goes with the slotted flat strips on live and neutral, they don't stand up to abuse as well as standard wall outlets do. Loose connections will be an issue for anything that gets plugged into a compromised outlet and daisy-chaining power bars compounds the problem. All three of my old (as in 10+ years old) SurgeArrest Performance power bars had one or more outlets in the center strip that were no longer usable until I opened them and bent the contacts back into shape when I did my SurgeArrest repair and follow-up tear downs.

It is possible to safely mix and match power strips for whatever purpose you have in mind, but you need to keep tabs on what gets plugged where. For manufacturers covering their arses and occupational hazard legislation, it is much simpler to say "don't do it" than worry about how all of the possible variables can pile up to create trip, shock, fire and other hazards.
 

jimmysmitty

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Funny enough the BE750g has a LED in the power button instead of off to the side. We use them for our work systems as they are not too bad on price and no one needs that much extra power if we have a power failure.

Unless it is our servers. Which we have at least 1-2 hours worth of APCs. Which are heavy. And annoying to swap out.
 

Daniel Sauvageau

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If it uses the same Infineon ICE1PC802 PFC controller as the 850W version did, the simple fact that its datasheets have been buried (there is hardly any trace that the chip ever existed on Google) tells me it must have been one of those picky or misbehaving PFC chips that got discontinued early due to design flaws.

Having a PFC controller which has issues with non-sinusoidal input is worrisome since the AC waveform before the UPS switches to battery power can be just about anything, the output waveform as the UPS switches from AC to battery is also going to be an unknown, as is the waveform when the load gets transferred back to AC. The APFC circuit needs to cope with all three transient conditions which can be much weirder than stepped approximation.
 

Daniel Sauvageau

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I'm expecting the Earth's rotation axis to change drastically because of it any second now. :)
 

nukemaster

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:)
My UPS has been plugged into a power bar for years(may as well let that surge protector take any surges instead). I used to have a power strip after it(no surge or anything) for manual load shedding.

This was a setup from many years ago(power adapters on piggy back plugs). Nothing took much power, it was just space consuming
 

Slobodan-888

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@g1abhi wrote:

"I have something to ask though not related exactly to the tear down.
When APC writes 550VA or 330W , what exactly is the intended capacity of load backup. Is it able to deliver around 330W of power , or in other terms can run 5 bulbs of 50-55W simultaneously. I know about the power factor that is considered to be 60% which gives the 330W value as 60% of 550VA."


It means that can deliver 550VA of power continuously.
Power factor depends of the load. Ressistive load (a light bould, heater,...) has PF of 1, which means that is can deliver 550W of power to those kind of loads.
If you are powering inductive load (motor), then the power factor could be around 0,5 and you could only power 275W motor max.
If the load is capacitive, it will also have PF lower than 1.
Computer PSU is mostly capacitive load (in combination with inductanse), so it will depend of your PSU. If it has power factor correction, and a FP of 0,9 (for example), you can deliver maximum of 495W (of INPUT power to the PSU).
 

Daniel Sauvageau

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A 550VA with a 330W power rating won't deliver 495W, it will deliver as much as 330W as long as the power factor is better than 0.6.

Another problem with speaking of power factors here is that the source is a stepped approximation, not a sine wave. If we go by the basic definition of PF=1 meaning a current waveform that matches the shape of the voltage waveform, then the stepped current waveform I have shown earlier is technically PF~=1 for a stepped UPS.
 

Slobodan-888

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@ Daniel Sauvageau

No. The max power is 550VA, which is 550W for PF of 1. And for PF of 0,9 of a load, it will indeed deliver 295W max. 330W is not the max power for loads that have PF better than 0,6. It is the max power for the load that has exactly PF of 0,6.
 
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