Using online UPS to power a system

[Indiglo]

Just found now a online UPS claiming 10000w, https://powerwalker.com/product/10122127/ available here in Sweden from a big tech and office supply store for €1500, so not so surprising one can buy similar units directly from factory for about half that before import tax.

You need to understand that a UPS is designed for IT Equipment such as Computer Servers, Routers, Switches etc etc.
On that basis the UPS can provide short term high power to allow the IT staff do perform a graceful shutdown of Computer Servers ie: a few minutes or provide low power over a longer period for devices like switches and routers.

 

[Leob]

UPS units are used in many different industries powering a lot of different loads, but very common in sever halls of course. And your point being? You think an UPS can only power switching power supplies in IT equipment but not in audio equipment?

People are running sound systems on portable power banks that employ the same technology, and seems to work well drive sound systems even if they are not designed exclusively for that purpose.

 

[Indiglo]

You're using the wrong tool for the job. A UPS is not the same thing as a portable power bank.
A power bank is something a busker standing on a street corner would use to power a small PA amplifier for a hour or so.
You won't be using a UPS or portable power bank as a replacement for a 40Kw generator to power a music festival for a day.
The 10Kw rating of the UPS is the battery energy storage not the ability to provide 10Kw of continuos AC Mains Power.
In data centres or critical infrastructure the UPS provides short term power whilst the onsite diesel generator fires up in the event of a power outage.

 

[Leob]

Did I mistype the URL and ended up at justbuyorrentwhatspopularaudio.com instead of diyaudio.com?

@Indiglo I think you missed to read the original post. I never intended to replace the generator with an UPS. I just want to avoid having to get a generator that is capable of providing many times more than the system consumes. The UPS happens to have the right combination of components to make it possible to use as a buffer for burst power. Those components happens to be the same as in a portable power bank, but with an UPS you can find units that can deliver more power. And a decent portable power bank can run 18" subs without a problem while charging at the same time, so it is clear that there is no problem running a sound system on an inverter connected to a battery and charge controller.
So the right tool for the job according to you is to use a 40KvA generator to run a load that draws 5000w? Even if will cost €1500 for a weekend including diesel?

 

[Indiglo]

Typically I will rent a 20-40kVA trailer but both the cost and efficiency is not that great.

If the generator can deliver 20kVA that is typically some 5-7kW per phase, leaving very little headroom.

The 40KvA trailer is great and provides really nice stable power and gives resonable headroom, but it does cost quite a bit to rent and run.

Perhaps a large inverter generator like a 7kW Honda will actually provide enough peak power, but seems to only exists single phase versions, do get very expensive and hard to find for rental in the area.

Assuming extremely compressed music with a 6dB crest that gives 5250w draw. In reality I would probably be down a DB or so from max and normally play music with 7-8dB crest, giving around 2625w actual draw.

there are some units below €1000 with shipping that can deliver over 10kW on 3 phases with a 3:1 crest factor according to the specs.

So add to that an old 3-phase 10kVA diesel

A 10kW generator is not enough to handle the peaks, been there done that. Even a 20KvA Atlas Copco trailer with similar size system could not run it at full power because voltage starts swinging when the kick comes in. That will result in bad sound and putting expensive equipment at risk. Hence I have been renting the 40KvA instead.

That correlates with my experiences using a 20KvA generator for a system drawing a bit over 10kW being somewhat underpowered.

keep doing as I have done through the years and rent a massively oversized generator. But of I wanted to do that, then I would not need to make this post, would I?

Obviously it is not ideal to run a 40KvA generator to generate less than 5000w average.

Please define what your power requirements are, at this point you have made a number of contradictory statements.

Nobody would use a UPS as a buffer for burst power, that's the definition of the wrong tool for the job.

Please consult with professionals who can provide guidance with your specific requirements.

I'm tapping out on this thread, its a waste of time.

 

[Leob]

Thanks, I'm not asking for advice on a specific system so not sure why you are focused on that, but initially it will be around 10000w RMS.

Not sure what you think is contradictory in that seemingly random collection of quotes, but I guess the problem is that you don't understand that with a 10kW RMS system, the average draw when playing typical music would be 5000w. 10000w draw would be if you are playing a continuous sinewave, and peak draw can be 20000-40000w depending on how dynamic the material is.

My focus is not what other people do. If you do what other people do because of a sheepish mentality and is incapable of formulating your own solutions and ideas I feel sorry for you, but if you can tell me why you think it wouldn't work with your own reasoning I'm all ears.

People do use inverters as a buffer when using inverter generators...without the inverter part a small petrol engine would really suck at powering amplifiers. The inverter in an UPS is not different, but where I'm not clear is now well the batteries would work to smooth out longer peaks.

 

[mikeAtx]

Another thing you'll need to watch out for is heat in the batteries. Your pack is going to be fairly large and cycled often. I know the almighty tesla failed around the ring for years and would go into limp mode. The fast charge discharge from hard regen braking followed by hard accel overheated the battery pack. I'm not sure they even made one lap. All the ev makers embed thermal sensors into their packs and they still have fire issues. I think the lipo chemistry is like bipolar output in a way. Hotter bipolar get, vbe drops, more current, more heat, until fried. Hence the thermal feedback component added to the output drivers. I don't know if the LiFePo has the same issue. The Fe may be more thermally stable than the more expensive cobalt chemistries. Too bad you can't wait for the new RAM. Early reports are quoting a 130kw generator as the power source for it and a storage of I think 90KWH. You could drive it to the show, hook it up, and drive it home!

 

[logsquared]

Have you considered running the sub amp from DC? Most switching power supplies can be run from DC. Extremly dangerous to have 300+ volts DC. However much more efficient than converting back and forth several times from Gen to speaker.

Or just buy a powersoft X4L and be done with it.

 

[Leob]

Another thing you'll need to watch out for is heat in the batteries. Your pack is going to be fairly large and cycled often. I know the almighty tesla failed around the ring for years and would go into limp mode. The fast charge discharge from hard regen braking followed by hard accel overheated the battery pack. I'm not sure they even made one lap. All the ev makers embed thermal sensors into their packs and they still have fire issues. I think the lipo chemistry is like bipolar output in a way. Hotter bipolar get, vbe drops, more current, more heat, until fried. Hence the thermal feedback component added to the output drivers. I don't know if the LiFePo has the same issue. The Fe may be more thermally stable than the more expensive cobalt chemistries. Too bad you can't wait for the new RAM. Early reports are quoting a 130kw generator as the power source for it and a storage of I think 90KWH. You could drive it to the show, hook it up, and drive it home!

That is the kind of thing I'm worried about. Depleting for about 0.5 sek, then charge for 1.5 for hours, and so on for hours on end, is not really a normal application. Pack doesn't need to be that large though? At least with LifePO4, which you can get with 50C discharge and very fast charge rate, they can deliver a lot of current in a small pack even if the runtime without generator will be short.

 

[Leob]

Have you considered running the sub amp from DC? Most switching power supplies can be run from DC. Extremly dangerous to have 300+ volts DC. However much more efficient than converting back and forth several times from Gen to speaker.

Or just buy a powersoft X4L and be done with it.

Indeed I have been looking at DC, but didn't consider running an AC amp on DC, and could not find any suitable DC amps. I would not like to run on 12v but at last 48v in that case. Not so nice to deal with 100's of ampere But with DC it becomes a bit impractical the voltage the amplifier expects, and not much equipment like chargers or inverters will accept those voltages, and I will need those even if I wont run the amps on inverter. So not sure if it is practical, but it is an interesting idea!

In what way would the powersoft help?

 

[daqvin_carter]

Some modern amplifiers with switch mode power supplies may accept DC just as well as AC. They just immediately rectify the AC. You would need a good list of what amplifiers work well just from DC.
In that case a capacitor bank would seem like a good solution. You just need some charge management for the capacitors.
Also this can be done with most computer power supplies.

 

[Pano]

10kW RMS system, the average draw when playing typical music would be 5000w

It would not be, but that doesn’t matter much for your use. Nothing run near capacity will perform well for a PA. As I think you have already stated.

It’s too bad that you don’t have a chance to measure the realtime current draw of your system. That way you would know exactly what you need for RMS and for the peaks. I’ve done this on several rigs but only measured the outputs for peak. The power input was measured long term RMS as that was all that was important to me.

You might not be able to correctly size your peak filler without direct measurement.

 

[Leob]

Yes, seems nice to skip another conversion just to have the amp convert it back!

Some modern amplifiers with switch mode power supplies may accept DC just as well as AC. They just immediately rectify the AC. You would need a good list of what amplifiers work well just from DC.
In that case a capacitor bank would seem like a good solution. You just need some charge management for the capacitors.
Also this can be done with most computer power supplies.

Yes, seems nice to skip another conversion just to have the amp convert it back! Would be a much simpler system, and will look in to how doable it is using existing components.

 

[Leob]

It would not be, but that doesn’t matter much for your use. Nothing run near capacity will perform well for a PA. As I think you have already stated.

It’s too bad that you don’t have a chance to measure the realtime current draw of your system. That way you would know exactly what you need for RMS and for the peaks. I’ve done this on several rigs but only measured the outputs for peak. The power input was measured long term RMS as that was all that was important to me.

You might not be able to correctly size your peak filler without direct measurement.

I was calculating with a crest factor of 6dB, which is very low. But it is nice to spec for the most extreme scenario, which I think that is for the music we play. But most of the time I would expect actual average draw to be half of that, so 1/4 of RMS. Would that correlate with your experiences?

I will verify the actual draw before eventually proceeding with the power solution, but have not got the subs yet...

 

[logsquared]

Some modern amplifiers with switch mode power supplies may accept DC just as well as AC. They just immediately rectify the AC. You would need a good list of what amplifiers work well just from DC.
In that case a capacitor bank would seem like a good solution. You just need some charge management for the capacitors.
Also this can be done with most computer power supplies.

This is the best "engineered" solution. Very easy to implement. Like I said earlier, extra caution must be taken with the high DC voltage.

I was calculating with a crest factor of 6dB, which is very low. But it is nice to spec for the most extreme scenario, which I think that is for the music we play. But most of the time I would expect actual average draw to be half of that, so 1/4 of RMS. Would that correlate with your experiences?

I will verify the actual draw before eventually proceeding with the power solution, but have not got the subs yet...

I do a lot of electronic misic events. With my subs I find the crest factor on the sub amps is around 12db for bass music and 8db or so with kick based 4/4. Seems counter intuitive, i know. My subs have Zmin around 60hz so kick draws more current from the amps. Bass music on my PA doesn't draw the current becuse the sub cabinet Z is higher at the dominant freq. This is the crest factor at the amp output. The amps do gulp huge momentary current for every kick/ bass line. I use powersoft amps, having 3 phase input is a game changer as far as line draw is concerned. And the PFC makes generator usage much more friendly.

Power conversion is what you are doing in the simplest terms. The easiest in my opinion is to buy a more capable sub amp. Second and less costly just buy more clone sub amps and use them at a lower capacity. Every amp you add that is powering the original speaker load will add more energy storage. Without PFC the instantaneous line draw may still be very high however. So, spreading the amps across the 3 phases of the gen would be ideal.

 

[Pano]

I would expect actual average draw to be half of that, so 1/4 of RMS. Would that correlate with your experiences?

Close, I tend to see about 16dB below peak so about 1/6 peak, or 1/5 RMS. Although I usually think the other way around, what is the peak above the RMS? Live music is normally much more dynamic than recorded, so peaks like kick drum can be very high. How do you know what your RMS current is? The best way is to measure it, but that might not be possible. You can sort of estimate it if you are running the amps into clipping, or know where your peaks are.

Of course your goal is the "save the peaks" so that value is probably your most important.

 

[Leob]

@logsquared
I have been thinking along those lines as well, even to actually power the amplifiers from other amplifiers But I guess doubling the capacity will net the same result.
A really overpowered setup of Powersoft amps would be nice, but will cost a bit more than I'm prepared to spend. But I hope the Morin amps will perform at least close. They are inspired by Powersoft designs, just like the CVR and Admark branded amps. So does have PFC and decent amount of caps. Main difference seems to be that they tend to have more caps on the output and less on the PSU compared to Powersoft in the comparisons I have seen.

Doubling the amps would probably be more costly than an UPS, even if I go with cheaper alternatives, and not sure which solution would give the more peak capacity for the money. But it is of course much simpler and nice to have spare amps instead, so makes sense.

 

[daqvin_carter]

Another thing to watch out for in your power budget is your low frequency drivers.
If you push your woofers past linear excursion you can expect a quick drop in impedance and an increase in power consumed. May show up in those crest factor numbers,
Some larger excursion drivers may have a bit of distance between Xlin and Xdamage.
Doubling up on the bass drivers/cabinets can push your power requirements lower in that case.

 

[454Casull]

Is your equipment running 1-phase or 3-phase power?

Maybe you could find some used equipment like this: https://tripplite.eaton.com/smartpr...webcard-option-usb-db9-serial~SMART5000XFMRXL

Line Interactive Automatic Voltage Regulation (AVR) corrects 208V nominal input from 167 to 260VAC back to usable 208/120V levels without consuming battery power

 

[Leob]

I have been thinking along those lines as well, even to actually power the amplifiers from other amplifiers But I guess doubling the capacity will net the same result.

Talking to myself here, but actually having amps powering other amps would of course behave differently than if you have separate amps running in parallel. Not sure exactly how though, but I'm guessing it is a bit different than if you simply had a couple of capacitors that you put in series or parallel.