Can I plug UPS to inverter?

[ak1ca]

Hello everyone, maybe a stupid question but since voltage here is really unstable sometimes, few days ago we didn't have electricity for couple of hours and when it finally came voltage was 185w which I assume is really low?, So my inverter does not have AVR build in and my APC ups does have so I was just curious can I plug my ups into inverter without any issues ?
Thanks ?

 

[pollenface]

I have done and all was fine

 

[timselectric]

Yes
No problem at all.

 

[svetz]

It depends on the inverter, it probably requires a pure sine wave output.

 

[ak1ca]

It depends on the inverter, it probably requires a pure sine wave output.

My inverter is modified sine wave, so I just tried it and ups makes clicking sound when inverter is running on batteries

 

[ArthurEld]

It depends on the inverter, it probably requires a pure sine wave output.

You are making me curious. I would think a UPS could be used to clean up the output of a crappy inverter.

 

[brum]

I was wandering the same till a couple of months ago. I have a SMA Sunny Boy inverter that is grid tie and does not produce power if the grid is down. So I was thinking about a pure sine wave inverter instead of the grid and some very limited consumption.

I dropped that approach because I got SMA Sunny Island inverter. When the grid is down the inverter can create an isolated grid and there will be sufficient power to get low-power devices working for more than a day. Such as the gas boiler.

 

[ak1ca]

Yes
No problem at all.

I have done and all was fine

Do you have pure sine wave inverter ? Cuz when I plug ups to inverter while running on batteries it's making clicking sound

 

[timselectric]

Do you have pure sine wave inverter ? Cuz when I plug ups to inverter while running on batteries it's making clicking sound

Yes
And I have 3 UPS's plugged into it.
Modified sine wave inverters are like black and white TV's. Old technology that should be forgotten.

 

[Northernchateau]

You will drive an APC UPS crazy if you do not have a pure sine wave inverter that holds steady voltage.
Modified sine wave inverters work just fine if they are powering a incandescent light or a heater and some AC motors.

 

[ak1ca]

You will drive an APC UPS crazy if you do not have a pure sine wave inverter that holds steady voltage.
Modified sine wave inverters work just fine if they are powering a incandescent light or a heater and some AC motors.

I am powering mini chia farm (mining crypto with HDDs), basically let's say mini server room that draws 230watts. Here where I live power outages are common, originally I had ups on it but the ups did not hold enough on batteries so I bought inverter and 100ah AGM battery. I thought inverter had AVR build in but I was wrong. So now I need to buy voltage stabilizer... Since voltage is not stable sometimes.

 

[Vigo]

So you want to use UPS as the ac input to the inverter? It should be fine as long as the inverter can limit what it pulls from the ups to something at or below the UPS’s rating.

Any inverter with an internal transfer switch is going to ‘sync’ to the grid on its ac input because it is staying prepared to switch over to it seamlessy. If you had grid directly charging you battery and no ac input on inverter, the inverter would not try to match the grid and the voltage fluctuations would stop. My Growatts also have various options in the UI that could stop it from doing that as well.

Using the UPS as a ‘conditioner’ between the grid and the inverter’s ac input should stop the voltage from fluctuating so much, but there is a limit to what it can adjust for based on something about a multitap transformer, only so many taps. It will still probably follow the grid’s frequency.

The ideal thing is called ‘double conversion’ and most cheap UPS’s and inverter/chargers dont do it. But if you Simply charge your battery from a frid-powered charger instead of using an inverter’s internal charger and then disconnect the ac input from the inverter, you MAKE it double conversion. It’s just less efficient because of more conversion losses.

 

[timselectric]

So you want to use UPS as the ac input to the inverter? It should be fine as long as the inverter can limit what it pulls from the ups to something at or below the UPS’s rating.

Any inverter with an internal transfer switch is going to ‘sync’ to the grid on its ac input because it is staying prepared to switch over to it seamlessy. If you had grid directly charging you battery and no ac input on inverter, the inverter would not try to match the grid and the voltage fluctuations would stop. My Growatts also have various options in the UI that could stop it from doing that as well.

Using the UPS as a ‘conditioner’ between the grid and the inverter’s ac input should stop the voltage from fluctuating so much, but there is a limit to what it can adjust for based on something about a multitap transformer, only so many taps. It will still probably follow the grid’s frequency.

The ideal thing is called ‘double conversion’ and most cheap UPS’s and inverter/chargers dont do it. But if you Simply charge your battery from a frid-powered charger instead of using an inverter’s internal charger and then disconnect the ac input from the inverter, you MAKE it double conversion. It’s just less efficient because of more conversion losses.

No
The other way around.
Inverter/ UPS/ load

 

[Vigo]

Ok. Well that way probably makes more sense if your loads NEVER exceed the ups rating. If you did it the way i was talking about you could still exceed the UPS rating for as long as your inverter battery lasted.

 

[pollenface]

Do you have pure sine wave inverter ?

Yes

 

[Lilikoi_Heavy_Industries]

My take on this (similar to others):

You should only do this on a pure sine wave inverter, modified sine is a gamble, you don't know what's going to fail. I had an air purifier that lasted being turned on a single time on modified sine, and any kind of voltage conversion equipment is also likely to be strange. I got to the point that I would charge power tool batteries on modified sine, but that's about it, and I think older tool battery chargers had bigger issues with it (hearsay).

Your UPS will not clean up dirty power unless it's a very expensive UPS in "in-line mode" or similar. Normal cheap UPS just pass the power through when being provided with power on their input.

And yeah, the person who pointed out you shouldn't be exceeding the UPS rating is definitely correct.

Nice thing? When you move your loads back from inverter to grid, they don't have to lose power for that cutover.

 

[Vigo]

Correct me if im wrong but don’t some UPS’s have transformers with multiple slightly different winding taps so they can switch to the one that makes the closest to ‘correct’ voltage? I dont know what that feature is called or which ones have it but im pretty sure it exists because its a little more clever than my usual inventions so i probably didn’t come up with it on my own.. ?

 

[RCinFLA]

A UPS pre-sync's to AC input sinewave zero crossing so it is able to bring up its inverter in sync with what was the AC input phase before it dropped. When grid come back on the UPS keeps running from battery for a while and gradually resyncs its inverter to grid before turning output back over to grid. Proper grid voltage range is also checked before turning over the load to AC input.

Problem with modified sinewave for UPS input is it does not provide a succinct zero crossing point so UPS does not have a sharply defined zero crossing to follow. Its sync process jumps around telling the UPS controller it has not achieved proper AC input synchronization so it will not take over AC output load.

Couple of other incidentals are AC voltage measurement/matching and possible power factor correcting charger in UPS.

AC voltage measurement is likely just a scaled AC sinewave full wave rectified average, like a cheap DVM. Not a true rms AC voltage measurement. Modified sinewave will read incorrect rms voltage equivalent on an AC average responding meter so UPS AC output voltage matching will be off. Not a showstopper in most cases but the UPS inverter will supply a slightly lower AC output voltage as the result of inaccurate AC rms input measurement of an input AC modified sinewave rms voltage.

Especially in Europe with its power factor regulations, the UPS battery charger might have a power factor correcting frontend. PF correction circuits expect a sinewave input. Some can be damaged if input is modified sinewave input or will shut down if too far off from a true sinewave due to high peak current in PF correction circuitry.

Many computer power supplies these days have power factor correction. This is why most new computer UPS supplies are now sinewave output. Old UPS's often had modified sinewave inverters to supply backup AC output. The old UPS's still required sinewave input to acquire proper sync.

 

[Vigo]

Gotta say, that’s the only specific explanation for HOW msw causes a problem with something, that i can specifically remember seeing. Granted, poor memory and all that. Thanks for taking time to explain. ?

 

[ak1ca]

My take on this (similar to others):

You should only do this on a pure sine wave inverter, modified sine is a gamble, you don't know what's going to fail. I had an air purifier that lasted being turned on a single time on modified sine, and any kind of voltage conversion equipment is also likely to be strange. I got to the point that I would charge power tool batteries on modified sine, but that's about it, and I think older tool battery chargers had bigger issues with it (hearsay).

Your UPS will not clean up dirty power unless it's a very expensive UPS in "in-line mode" or similar. Normal cheap UPS just pass the power through when being provided with power on their input.

And yeah, the person who pointed out you shouldn't be exceeding the UPS rating is definitely correct.

Nice thing? When you move your loads back from inverter to grid, they don't have to lose power for that cutover.

Thank you for your answer, I found locally https://www.apc.com/shop/no/en/prod...martConnect-Port-SmartSlot-AVR-LCD/P-SMT750IC this ups, will this work with my inverter ?