What's inside a UPS
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- เผยแพร่เมื่อ 27 พ.ค. 2022
- Exploring the inside of a UPS (uninterruptible power supply) and explaining how does it work. This one is Back-UPS CS 350 from APC, probably 350VA and peak 500VA. It's a simple type with an iron transformer and a modified sine wave output. It converts 12V from a sealed lead acid battery to mains voltage during power outages to back up the load, usually a computer.
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The seamless switching from mains to ups and vice-versa is so satisfying. Great video, wouldn't be surprised if you did a schematic of it lol
does that mean that the PC for example stays on
@@tylern6420 Yes, it does, but remember, it's only a short term backup to give you time to save your work and shut down the PC correctly. You get literally only a few minutes.
Bigger and more sophisticated units can keep you on backup power for considerably longer, but those are expensive pieces of kit.
Yes, all depends on how much your comp uses power and how much capasity of the battery is...prbly 5 min. Is normal to save.. better is autosave!
@@tylern6420 Even with like a second or two of no power (as long as the PC is not fully loaded) it will still stay on because of the Capacitance
Ya want the schematic
In my whole life first time I saw transition from mains to inverter... Thanks
I don't love the display delay or the quantization noise but the sample-hold-zoom offered on the digital scope brings it back into the happy column. I want one.
Yeah, that was interesting.
I have the 800 model. it uses 2 batteries and starts without AC.
I bought 5 of them for $25. None were working, and came from university of Ottawa engineering lab.
I repaired 3 of them with the parts from the other two. Knowledge is power :)
They are great and have saved my ass on many occasions.
Last time was last weekend when we had a freak storm that knocked out the power to 300K people for more than a day.
Expecting more freak storms in the future as the environment goes to shits ...
This one would start off battery as well, he just needs to hold the button a bit longer
You can start it up on Battery, if you push the button for three seconds. I used exactly that type of UPS as a inverter for my RV for years.
Edit: it was super reliable, by the way. It was on basically 24/7 and ran my refrigerator, various lighting, my turntable, audio amplifier and various chargers.
It was the bigger 600VA-variant, though, iirc.
Actually need to keep the button just for 1 second or more. Release when UPS is started form battery.
Some inverters you can power back on with just battery power and some you can't, it is to stop people from switching the UPS back on after the UPS has shut itself down and its connected computers, in the event of a power outage.
@@tyronenelson9124 absolutely. But this particular UPS has a built in override-function. It performs a "hard start", if you press the front button for longer than one (or maybe three...)second(s). If you connect it via serial or LAN (depending on the model; the most recent ones have also USB iirc.) then you can disable that function in the factory settings menu in the software. But if you press the button for more than 10 seconds, release it and press it again, it will turn on anyway, even if you disabled the override function in the software...
@@albinklein7680 Mine does exactly the same problem with mine is that it constantly beeps the whole time on battery power, it also has a LAN port possibly to alert the network of a power outage.
@@tyronenelson9124 mine also beeped constantly. But I just disconnected the piezo speaker...
Very nice to see a UPS here, i have been considering shipping you one for years.
Line-interactive UPSes pretty much always use iron core transformers, all the way up to 5KVA.
APC even has a patent on a design using the transformer to step-down the voltage for charging, and step-up when running on the inverter - but this system is only used on the pure-sine line-interactive UPS models.
Double-conversion models online doesn't use an iron core transformer, but instead they have a very high DC voltage on the batteries, so it doesn't have to boost the voltage that much.
Common voltages for these UPS types are 120v (eaton), 72, 96, 192 and 384v for APC.
So 12, 24, and 48v UPSes is pretty much always line-interactive using an iron core transformer.
sad they don't use a spwm chip to get a sine wave with that transformer
@cliffmatthews7393 I got Trust 1300 VA UPS from friend (it's batteries had failed) and it seams to keep trafo on constantly, it charges battery from one winding for instance. Otherwise seems similar as this one, when working from batteries gives out same square wave.
*FANTASTIC* Your thorough circuit explanation and testing is concise and perfectly clear for anyone wishing to understand the power end (and control circuit operational design) of this UPS. Tons of knowledge are conveyed in every second of your videos! Thank you.
I remember I took a dead UPS apart once, this one looks like a toy in comparison to the one I found. It still used a transformer to step the voltage up. I now use that transformer to step mains voltage down to 12 volts and lots of current. The high voltage side only measured 2 ohms DC resistance so I know this transformer can handle some serious power. I can also use that transformer as an auto transformer as it has multiple taps on the high side, so I run big my fan at 120 volts, running it on half the voltage, I don't get a hurricane in my room!
That's pretty neat! And I have a couple professional grade Tripp-Lite UPS's and those suckers are so complex inside compared to the APC in this video! The big one is almost 2000VA but it runs on 24V. The cool thing about the Tripp-Lite ones I got is they'll start on a battery. 😎
We need more of these inverters videos
12:25 Většina UPS je schopna studeného startu, takže by měly jít nahodit i bez sítě, zkus to tlačítko chvilku podržet. /
Most of UPS is cold-start capable, so they should start without mains power, try to hold the button for while.
This guy knows. :)
Can confirm. I own the same UPS as in the video, you have to hold the button to get it to cold-start.
To start on battery power, maybe you have to push the switch for longer duration.
Yes
Well done diagnosis. You have a knack for figuring stuff out.
I'm impressed with the control circuit
Waiting long for this complex APC Online UPS.
Thanks Diode.
You're a good teacher mate! Loved watching the signals change.
That's the joys of learning the craft!
Great video as always.
Good repair and excellent explanation with the oscilloscope sine/square waves.
Always wanted to watch such a video thanks 😊
if it's the same as my unit, you have to hold the button to get it into 'Test' mode, which will initiate without mains powering it, providing the battery is good.
Just a general "Thank you!", your work is excellent.
Thanks for your support and appreciation ;)
Great topic. Enjoyed this video. THANX for your efforts.
I've repaired a few of these; the problem always seems to be overcharging the battery, and is caused by the small blue through-hole capacitors failing.
Exactly. I'd noticed that too on my UPS and decided to turn down the voltage a bit from 15 volts to 13,8 volts. But sadly I'd turned the wrong potentiometer first and I noticed nothing had changed.
So I turned it back to almost original position and tried the next which was the correct one. Voltage gone down to 13.8 volts and then I'll thought yes that's good, I have unplugged it.
It worked nice until I plugged it in again in mains. The relay like this: click click click rrrrrrrrzzztttgtrrrrrrrtr and then the magic smoke coming from one of the big power transistors.
Now I'll think it's gone :( I'd fear to plug it in again to be honest.
Now it's laying here since years taken apart and sadly I can't simply just throw it to trash. Because it saved me hours of work thanks to the UPS.
@@gumpi5 Sounds like the damage was caused by turning the wrong pot in the first place, and possibly the second pot, when you change the battery charge voltage you are also affecting the PWM and also possibly the duty cycle of the output of the UPS, inverters are not really affected like that.
@@tyronenelson9124 The battery voltage does not affect the PWM because the frequency and pulse width depend mostly on the passive components which set their values, such as an RC combination which is fed either by constant current or regulated voltage or both, and those circuits are often ratio-metric, meaning whatever the applied voltage it will give almost the same timing, much like the 555 internal comparators.
The UPS should be able to work properly anywhere from 10 to 15 volts, so his small voltage adjustment is definitely not the cause of the power transistor(s) failing. It is much more likely that he adjusted wrong trimmer(s).
The transformer is also used to charge the battery as well and the output voltage usually is about 16VAC for the 12VDC models.
Really cool video......thank you!
you are awesome as usual , thanks a lot
I use the specific UPS for some years. It is a rather noisy one (the transformer is humming) but can handle my router, my screen, my pc and a led desktop-lamp + my telephone base for about 2 hours. By the way I have modified the switching circuit according to the description I found in TH-cam to reduce the temperatures for specific components
Great Video!
I hope you get your hands on a sine wave ups, I’d be very interested in seeing you talk about that
I got a couple of circa 2000 era UPSes circa 2004, with flat batteries, for $10. I had the brilliant idea of just using a couple of car batteries to power them. And then discovered that the transformers were only ever designed to sink the 600kJ of energy contained in the two 7Ah batteries.
So in the second one, I drilled some ventilation holes and hooked up a fan to a sensing circuit. That one lasted for years before I decommissioned it.
My current UPS is a lot louder because it's an online true-sinewave variety with roughly 10 batteries. I'm not looking forward to the date when I have to replace those batteries.
Interesting how the dead time circuit and the xtra transformer winding deals with voltage from the load
I have the same UPS (maybe a different number on the front), around the same age. I recently got a new battery, they're fairly cheap, 12V 7Ah. Put some tape over the piezo so it's not as annoying.
Very interesting!
I was expecting to see somewhat cleaner output though - at least an inductor or simple LC filter on the output to smooth out the very quick voltage rises and ringing that can cause problems for some loads. But the switchover from mains voltage to inverter and opposit was very smart indeed, with no gaps or "bumps" where one half wave get extra long (not even when switching back to mains voltage - which is the hardest part, since it has to be synchronized)
I suspect one of the reasons the control circuitry is performing phase matching it to prevent arcing in the relay during the switchover from inverter to mains or vice-versa. If the relay switches out of a high-current inductive load condition into an opposing voltage, it can momentarily bridge the mains into the inverter via the arc inside the relay. I had this happen once while designing a homemade UPS, and it killed the inverter connected to it.
I believe it is also possible to mitigate this effect by using TVS diodes on both sides of the relay, as it will limit the maximum voltage across the relay contacts, even when inductive loads are connected. An RC snubber can achieve a similar effect, but can have problems with modified sine wave (as mentioned in the video).
I too once built a homemade UPS, and had that exact thing happen! Took me a long time to figure out why the inverter blew up, but nowadays I know why cx indeed it was because of that same reason, the arc inside my relay bridged mains into the output section of the inverter, blowing all MOSFET's completely!
My friend has a friend who works at this Schneider factory in Bangalore,india and i bought a ups from him at half the retail price and i immediately took it apart. the construction is pretty nice. The model i bought is br1000g and it uses an smps to make the 24v battery voltage to 300v dc and then a full h-bridge to make it ac. Much more efficient than iron core transformer, it has an auto transformer for the avr function, also supports extra batteries to increase run time. Runs my power hungry desktop for 40m while gaming (350w consumption) or for 1hr 20min at idle like watching TH-cam. (130w consumption).
Damn buying products at half price and direct from factory sounds awesome.
On a 3kw UPC I took apart I found 2 of those small transformers that were sensing current on the output and input.
14:14 peak voltage is important for sw.power sup. cuz capacitors have small reserve for over-voltage
Should be fine unless it's too high. Like over 400V.
I’ve got a lot of like new ups systems… Ranging in size from the one in your video up to the size of a refrigerator. And everything in between.
I wish you were closer to me and I would give them to you to tear down for your channel. If anyone ever watched “Ausie50” here on TH-cam, ……then you’ve probably seen something similar when he showed tearing them down.
Years ago he’s the guy who got me interested in going to industrial scrap yards and learning about electronics. Now I have my own lab and metrology business.
I really miss that guy……rest in peace
If you hold the button down, some models will start up on battery power. There's more information in some ancient TH-cam videos with people that speak very slowly.
that made me chuckle
By just pressing the button momentary would only make it beep. Pressing and holding it would make the unit actually make it turn on. I've worked on a few of these in the past. Hope it helps on a update if possible. :)
Thank you
I always avoid these type of UPS, but honestly it is not too bad. The fact that is matches phase very well on switching, adjusts the PWM as battery goes down, and very fast switching (in less than a half of the cycle), shows it is not too bad. The rining / overshoot, is a bit worrying, but I guess many loads will deal with it fine. I usually use EATON true sine wave, on-line topology UPSes, they are more expensive and less efficient due to constant dual conversion, but provide very clean sine output, always regulated output voltage (so even if mains go lower, they regulate the output), and zero time swtiching, plus they don't need to use relays for that. I did open one to replace a fan once, and it was rather complex beast inside. I also like my EATON UPSes, as they have really nice monitoring, and they show voltage, frequency in/out, power, power factor, and when connected to computer using USB or network, you can even make graphs, etc.
Thanks for the video.
Beauty show!.
good phase transition
Wonderful
5:25 i assumed it worked like this: the input is connected to the output through a relay and the transformer is used as a battery charger but when voltage disappears the relay actualy switches the output off before turning the inverter on so that it doesn't backfeed into the system.
I just got a comparable Tripp-Lite UPS which uses a somewhat similar topology. I was wondering about the two "extra" transistors and now I know what they might be for.
I see cheap UPS where same transformer is charging battery, but it has extra windings switched by relay. When charging, some windings are connected to mains, when mains supply is interrupted, relay switches to other windings for output.. Only, now I don't remember exactly which windings where which.. 😂
Strange thing - why cheaper UPS have bigger heat sinks?? 🤔
Great video, as always! 👍
Hi, would be very interesting to have a close and detailed look at the (big) Transformer. The idea is to reuse it for a classic linear power supply; What power can it handle long-term? Is the insulation save enough?
I have this exact model still in service pretty sure if you long press the power button 5 to 10 seconds it will start without AC mains.
Interesting use of a shorted turn device, or at least, not one I'm familiar with.
I bought three APC rack mount UPS units, around 1.5kVA each. Thier internals are far more complex than this, and the main boards are the size of football fields by comparison. I'm inspired now to get them out, see if they're serviceable, and 'scope the outputs. I was given to believe that they were TSW, but I never verified that.
This video would seem to pour scorn on those other videos which show people modifying these small units for long term use. If those heat sink blocks are just a short term thermal dump, then long term operation would surely destroy those transistors in a very short time.
Most UPS of this size are only intended to maintain your equipment just long enough to save your work and shut down properly, not for long term running.
that transformer is a treasure.
Thanks.
tnx
I have the 1500VA model with two batteries (broken, need to seek replacement), this has one fan at rear side.
However i read (this line of) APC UPS are sensitive to (lack of) ground, and in South America many places has no ground connection.
While on battery alone, long press the button to switch UPS on.
The time it stays on while on battery depends on the power draw: high power draw, short duration while on.
UPS shipped with maintenance free lead acid batteries.
UPS shipped with a CD with drivers and an application that showed how many minutes till shutdown in case of power failure. On windows, it could shut down the computer when battery got low, if user ignored shutting down.
I believe same transformer is used to charge the battery, they most likely use active rectification using same MOSFETs. Check some of the APC patents, they have a lot smart cost-saving measures, to reuse same components to make it bi-directional.
I have a similar model protecting my TV. It's hooked up to a deep cycle marine battery. I can get 4-6 hours out of it with just the 65" oled tv on it. Mine has 8 120-volt standard outlets on the back. Only 4 are battery backed up
keep in mind that in some UPS, the battery isn't isolated from mains. Also the transistor heatsinks and the transformer might not be designed for a continuous operation, as they assume a smaller battery that quickly discharges.
Thank you for that! Any chance you can do the full H bridge circuit with reverse battery charging through the main/Hybrid transformer? (ie no switch mode battery charger).
i recently learned what was in mine a few months ago when the battery decided to melt when it failed. its still currently sitting in a stainless steel bowl cause it has actual holes in it that i have not had away to get it deposed of properly yet aka no way to drop it off at an eco place. so i stripped the whole thing apart and kept it for parts or things as i don't trust it with a new battery but the unit did reach over 10 years old so eh.
What does a capacitive dropper supply do on the artificial sinewave? Can we watch it explode?
Where I used to work I had about 8 monitors and like 3 pcs. That brand would break constantly and policy was to throw them out instead of replace the battery. We were not even allowed to take them home or anything. They along with every piece of electronics purchased by the municipality in the last 30 years sit in the old lockup facilities under town hall. Crazy ehh. I asked for a piece of hardware from the 90s once and it was a hard no. Same with a usb cable that was 'taken out of commission' and put in an on-site room with literally hundreds of old cables hanging on a wall. If you wanted to get in there after hours you had to break a window in a glass box for the keys. It was the smallest hammer you ever seen. I was a supervisor being groomed to run the place and even I couldn't access any of their coveted garbage. Garbage to them anyway.
Nice!
Nice one. I'd vote on a power factor meter since the frequency meter was already explained by Fran and the USB chargers are ubiquitous on your channel :)
uh correction APC units can be powered on with battery only.
All models have this feature. You need to push and hold the button between 5-10 seconds. This puts it into test mode when mains is connected. If mains is not connected, it starts the inverter in backup mode.
Thank you for the video. I have a few of the ES 700G UPSes (the ones that are like big power strips) and I'm going to modify one with a bigger battery (the normal one is only between 7 and 9Ah so gonna put a 150Ah battery in). Those low battery beeps gave me power failure anxieties, although the beeper in yours seemed to have a really strange pitch variation?
you should be able to find schema for this at Internet. I use 24V version which I have to fix few time, most changing capacitors in charge pump which supply op amps.
When no mains is present, you have to press and hold the power button for it to power up on battery, it'll then power up, though being so small and being a squarewave inverter, it's not the best really unless you're running resistive loads like lightbulbs or small heaters...
Some ups using same transformer for backup and charge (in ups with autotransformer for regulate mains voltage), in charge mode this transformer get very hot and overheating battery.
1st Hold the APC power button for a about 10 seconds and it should start without having to power it from AC. 2ed Some APC units will not power on until the battery is charged to a specific battery lvl but can be bypassed by holding the APC power button for about 10 seconds.
Inside a UPS (United Postal Service) is just full of slave labour in a warehouse where we deliver your packages
12:32 They do start on battery, i know because i use them as low power inverters.
Just hold the button down until it beeps and it will stay on.
I have ripped the buzzer out on mine because it's annoying.
I have the same UPS and it is possible to just start it withotu mains, I use it as mains supply in car from car battery
I got the same ups but different model (cs-500). That thing will power on without battery. Also, you need to press the power button for a couple of seconds to power it on from battery without plugging into mains. That thing has a nice features in there like fiddling around its settings and stuff.
In this model to start up whithout mains press on for 8 secounds.
I have a similar one, for some time I’ve been thinking of hacking it to get 12v output when mains are off because the devices I have on backup are 12v. It could be nice to get DGW to show this hack.
I wonder why that big a** iron core transformer doesn't seem to be LPF'ing the waveform to be more like a sinewave? IIRC, big mains transformers have terrible frequency response and often don't even work right with another mains frequency, and that's why you can't use them for a tube amplifier output stage. But this one seems to be passing the sharpest transients unabated.
No, an iron transformer does NOT turn a square wave into a sine wave. This seems to be a common myth.
@@DiodeGoneWild
Ok, but isn't every transformer a band pass filter? Where does such a transformer start to roll off approximately? Are audio frequency transformers, at premium cost, a rip-off and could you just use a center tapped mains transformer for a push pull tube amp (not single ended, because that would need an air gap)? That would be awesome! Never tested such a transformer's frequency response, honestly.
Or are there other reasons, like resonance/ringing, why you shouldn't use one?
@@westelaudio943 AFAIK most of the low-pass action of a normal transformer comes from leakage inductance which. Regarding audio use, you definitely can use power transformers as audio transformers. The downside is probably lower inductance and earlier core saturation limiting power at low frequency.
Presne toto som mal. Fungovao to. Vypadol prúd, ale počítač aj monitor bežali ďalej bez toho aby sa reštartli. Mal som viac ako dosť času uložiť čokoľvek na čom som pracoval a systém vypnúť bez problémov. Asi dva razy mi to pomohlo. Lenže je to obrovská a ťažká krabica a vzhľadom k veku akumulátoru som sa rozhodol ju zrušiť. Zatiaľ nebol žiaden výpadok prúdu, takže už pár rokov fungujem bez toho. Ale celkom pekné zariadenie, fungovalo.
5:20 Chargers are not rated for full power in the inverter UPS's. Instead during the normal operation rectified and power factor corrected DC flows to the inverter and powers the load. The battery charger is separate and slowly charges the battery when in normal use. When power is lost the DC/DC converter starts up. For the time it takes to start up power is drawn from the high voltage bank of capacitors.
Of course, there are two basic types of ups units. Not sure their names, but one would be your basic ones, "not online" or off-line type, while the other does remain on-line all the time. Amazing spelling. Thx.
ive always been confused with my apc 1500 because its got 6 plugs on it but they are all out of order and i duno how to plug all the stuff in. i usually put stuff in order buy theres gaps inbetween each plug.
Plz make some video on SNES controller USB interfacing
18:24 is that relay made in India?
Yes😲
Mulțumim!
Thank you too my friend
I have exactly the same model
I honestly was expecting an ElectroBoom moment at 11:18 :))
While I was a student, I would buy old 'broken' UPS for 5€, replace the battery or make extension leads with car battery connectors and put on it normal mains plug. So UPS can run the pump and furnace for central heating in case of failure. Also to keep battery charged.
The motor in circulating pumps does not really like this quasi-sinusoidal waveform. They are buzzing and the efficiency is worse (ei. it warms up more). Probably won't do damage, at least in the short term. Modern circulating pumps start with a rectifier on the input and using an inverter to run a low voltage 3-phase motor, those have no problem with any waveform, it would probably run even from 325V DC without any problem.
@@mrnmrn1 Motor does not like it, but it still work.
My main concern is high tension spike on transistors, and if motor is too high power, they can burn out.
Also, it is not ideal to start the motor while on UPS, but UPS can keep it running.
Some of these can tell the difference between a battery and a PSU as they detect the ESR of the battery, they would give an error if the battery is not detected.
What if put an inductor on the output to improve the pwm wave?
6:30 One of them is for load current measurement.
This UPS can turn on only from battery as well, just hold the button for a while
Nice video and that ups isn't really simple. I have few for driving the pump for hot water in my house heating. They are very simple. They use 1 big iron transformer as inverter and the same to charge the battery and supply the electronics. The inverter is square wave without any feedback. Just uses 2 MOSFETs and cd4047 to drive them and that is the only one ic on the board. Everything is made of descried transistors. They even don't use diodes to rectify the voltage. They use the internal diodes in the MOSFETs. For protections there is for low battery and 2 fuses. They have about 3sec to transition, but that's not a problem for their purpose. They use an optocoupler with 2 burning resistors to sense mains. I have used them for many years and sometimes the on off switch fails and the heatsink is too small so MOSFET can fail. The pcb is too thin and the thick wires from the transformer can break the pcb. Anyway it's cheap and works well with small induction motors.
I hope someone read this 🙏
I just did. And no it's not simple. Maybe if you're an EE or something😀
I have a USV without the fat Transformer. Only PowerSwitchingSupply Technik with a Systemfan, LCD Status and 3x 7Ah Accu.
I think you have to press and hold button to turn on on battery
I don't understand what this guy is measuring at 13:30. When he changes the input voltage, the output pwm should not change because the output load is constant. Unless he is measuring the input current which changes with the pwm. Another correction, this ups should not be used with inductive load also. I tired to use a modified sine wave with a flourcent bulb and choke. I killed the choke in 5 minutes.
One can use this ups to charge motor bike battery, 12V 7Ah lead acid
12:12 just do long press on button and its on from battaty without mains
I disassemble the exact same model today😂
At 18:33 you said coil resistance is not mentioned but what is the 175ohms on the relay?
Just an FYI.. UPS always run on inverter... it just switches the input from mains to battery... Thats why your devices don't get destroyed on voltage surges...
Lower volteeeege higher volteeege. sorry but it was just too funny :b. Great Video as usual
How can I fix ups C's 650 continuity on ac out put and all lights are flashing and DC out put is 4.9v