UPS vs inverter

[bob g]

following along with the inverter theme, i offer the following.

i have been studying the architecture of inverters, both standard and those that

are the basis for UPS systems.

when you compare the sine wave versions of the ups inverters with the other standard inverters such as xantrex, outback etc, i am hard press to find how the

ups inverter is inferior to those that are built as dedicated inverters, save for

perhaps in the cooling dept (heat sinks/fan)

those built by companies such as apc certainly don't appear to have cut any corners, and i figure they probably have built more inverters for their ups's than

all the standard inverter companies combined.

understanding also that the ups inverters are a bit less efficient and have a higher idle current requirement, likely due to the fact that they have charging circuitry, battery management, and all sort of other bells and whistles needed for

the job at hand.

also seems like maybe the ups inverter ought to be a better unit than most of the standard inverters because of liability issues. not sure xantrex/outback or others offer 25k dollar policies for damaged equipment and loss of data like apc and other ups manufactures seem to have to offer.

just curious why more of the ups inverters have not been altered to become full time inverters?

looks like a better fan/heatsink and a big battery bank and you are set to go?

i had always thought it was because of the ups inverter not having any surge capability to speak of. this is clearly not the fault of the inverter, but rather

a side effect of a limited battery capacity. can't surge if you don't have the underlieing battery capacity that can deliver the amps needed and do so without dropping below the low voltage cutout of the inverter.

what am i missing?

bob g

[scottsAI]

bob g,

I wondered the same thing at one time.

My study of the APC SmartUPS 1k, 2.2k, 3k, 5k had the following results.

UPS has large output transformer, it gets rather warm without any load.

Test of 3k UPS, transformer 115F in 70F room. Idle current of UPS is 48w. Not charging battery.

UPS is aware of load, shuts down if load exceeds its rating.

I tried large battery without much change.

Idle power of 1k UPS is 24w, my trip lite 1k inverter is 8w.

3k UPS will start a motor, no success with 1k UPS. Soon to try 1.4k UPS.

Mod sine 1k Inverter will start a motor, motor gets warmer than I like.

Have fun,

Scott.

[bob g]

Scott:

thanks for the input

here are some of my results

apc 1400xl (rack mount extended run capable with up to 10 battery packs)

rated at 1050watts, and will carry that amount no problem on a resistive load

and maintain a very good waveform that appears to stay within the <5% total harmonic

distortion spec.

it will no way start my 8 inch bench grinder which wants ~20amps for 2.3 seconds to startup.

connected to a 225amp/hr battery bank it will deliver enough guts to start the grinder reliably without tripping out.

stepped up to an apc 2200net tower style, rated at 1600watts max into a resistive load (2200kva)

try to start the same bench grinder and the thing just trips out before the grindstone can make a quarter turn.

attached 34amp/hr 48volt battery bank (twice the oem pack rating) and it will start the grinder in just under 2.3 seconds without issues. it will handle 1600watts resistive and maintain a very good sine wave as well.

it would appear that these units can deliver a surge for at least twice there kwatt rating for over 3 seconds reliably without tripping out.

i have not tested for how much overcurrent they can deliver on a continous basis before they trip out, but i suspect it won't be much more than maybe 10% on a continuous basis.

they do need better cooling for sure,

also of note, the 24 volt units seem to have an idle current of around 25 watts, and the 48volt units are closer to 50 watts, which precludes their use for standby use for a lot of folks with limited power generation or storage.

seems like a micro controller project to sense line loads and then start up the ups inverter would eliminate the idle current issues, and then shut down after the load was served?

also i wonder how much current it takes to cover all the other functions of a ups that a standard inverter doesn't have? maybe some of which could be removed?

bob g

[scottsAI]

bob g,

Good stuff Bob! Will go back and look at the bigger battery option for starting motors. 300w motor did not start with 1kw unit, (used 4 12ah batteries) with 200% over load should start!!

Looking up the magnetizing currents of a transformer it can be 2-5% of rated power.

48 watts is below the low end of the range.

I suspect the internal circuitry is frugal with the power.

Wanted to change the relays, to put different transformers on the output.

Small with light load... quickly adding in more to make it for full load.

Looking for a schematic, NO luck so far.

To change transformer and: Wire the output for 220Vac. The 3kw UPS has two transformers should be able to connect in series. Start my well pump.

Have fun,

Scott.

[PaulJ]

   I have a big APC smart UPS 2200 sitting in my power shed as a backup in case my main inverter fails.

   A couple of points:

   1) The standby power draw is horrific compared with the off-grid inverter; 50W compared with 10 - 15 or so. Overnight when only the fridge is running the APC UPS would be the main power draw.

   2) The 240V neutral output (I'm in Australia) is connected to 48V battery -ve, i.e. the unit is not electrically isolated from the input to the output; can't really be connected to household wiring in compliance with local electrical code.

   I would use it in a pinch running the frij/TV/ a couple of lights off extension leads if I had to but this would probably void my insurance if anything went wrong, a permanent hookup would be out of the question in my opinion.

   Paul.

[HaroldCR]

 This is perfect timing for me.

  I live in Costa Rica, and have a need for micro-hydro projects to be built. Inverters are expensive down here, but, I'm headed to the USA tomorrow, and am looking into gathering a few "take-out" UPS's. IF I find some, I will ship them down, and use them for people in remote locations, that have a water supply.

  Most people here use a fridge, and, maybe a clothes washer, Lights and a television would be the most they would have.

  I know nothing about Electronics, and recently, had my Computer connected UPS get blown out by a lightning surge. Computer is fine.

  IF you guys get a way to put the "on demand" feature to a UPS, I am all ears.  I will gather some computer fans, and modify the UPS's I get, for better cooling. Maybe a timer of some sort, for night time, running the fridge ??

  I plan to wire up 24V Battery system to the hydro generator. This stuff I know about. 4 Golf Car type batteries will be the power source for the inverter.  I am looking for low voltage lighting for the houses. Might check into LED's and make some fixtures for them.

  Might just build a small business out of this stuff, as I had back in Arkansas in the late 70's-early 80's.

  Thanks for any updates or other info.

  Also, is it possible to step up a 12V system, to run a wheelchair motor at 24V DC

  It is another project I have, and need the full output of the 24V motor, from a 12V system A second 12V battery is out of the question. It's on a portable sawmill I built.  Thanks again.

[bob g]

apc makes a hardwire kit for some of their ups units

so that they can be hardwired into a system, not sure of the NEC implications or

how the UL or CE certs are affected either.

i really didn't pay that much attention past reading about the hardwire kit availability.

one would think if the unit was hardwired in, it would have to meet UL certification

and the NEC codes as well?

something i will look into

bob g

[wdyasq]

Bob,

Something I've wondered about and never tried ... but might get positive results..

Take a small motor and 'spin-up' a suitable size AC motor with said inverter/UPS, connect to inverter/UPS with no load - maybe it has a flywheel. Use the inertia and generating ability of the now spinning motor to start a regular electric motor. Shut down the inertia device.

This would hopefully be controlled by a microprocessor or set of capacitors and relays/resistors and be autonomous.

Just one of the crazy ideas derived from noticing how 3PH rotary converters seem to help start larger things.

Ron

[oztules]

I use the fridge/s for this purpose... by default really.

When I have the UPS running the house, it has 3 fridge/freezers possibly running at the same time. Provided one of them at least is running, the 1hp jet pump starts instantly (induction motor). If no fridges are running it is a little slower to start up.

So it would seem the fridge induction motors are helping with the surge currents that the big water pump otherwise dumps on the UPS.

So yep... will work.

It is probable that a large starting choke in series with a small induction motor with sized flywheel, which switched the choke out after start, would aid in starting a larger induction motor with a large start up torque.

For low start torque applications (centrifugal water pump etc), perhaps the choke system would help do it anyway.

..........oztules

[Jon Miller]

Hi Bob,

"just curious why more of the ups inverters have not been altered to become full time inverters?"

Lots of people do not realise the potential of UPS's, there are people who mod them with remote start and line voltage detection but tracking down the information is hard.

"looks like a better fan/heatsink and a big battery bank and you are set to go?"

In my experience this is fine to do.  I have not moded the fan system yet but I shall be soon, like wise with remote start up.  A line voltage detection device could easily be built with a PIC controller.

"i had always thought it was because of the ups inverter not having any surge capability to speak of. this is clearly not the fault of the inverter, but rather

a side effect of a limited battery capacity. can't surge if you don't have the underlieing battery capacity that can deliver the amps needed and do so without dropping below the low voltage cutout of the inverter."

The surge of the UPS units is not great really, 1.5 times rated power, I think UPS manufactures are just driving there units harder then most power inverter manufactures do.

With regards the issue of starting inductive loads, starting up a smaller unloaded induction motor helps to start much larger induction motors, typically those that have a speed related stater winding set up.

"what am i missing?"

The high standby current is the issue sopping people using them more often.

Again a simple PIC controlled remote start up with line detect could work very well to get over this issue.

Regards

[bob g]

has anyone considered reverse engineering one of the ups units, so that

one could remove the functions that are unnecessary to inverter function?

i realize this is not a simple evening project, and would take some time

but it should be doable i would think?

apc and others won't provide a schematic, and they don't teach inverter design in

any school i am aware of, so it would appear that to learn about inverter design

you gotta have a degree in EE and then get a job for one of the inverter manufactures.

they have done an excellent job of keeping what they know in house, only ones that seem to be able to crack these things are the chinese, and you know they sit around

reverse engineering anything and everything at will.

i am not pushing for a diy inverter so to speak, but is sure seems like it ought to be possible to reverse engineer a ups in order to understand how to alter it to become a  more useful inverter for our uses.

it took me about 6 months to reverse engineer the dl305 plc system, and i was told that could not be done, and there was no way of getting a schematic either. i learned alot in the process, part of which came down to the understanding that for my needs i could build a microcontroller based system of my own design to get my job done.

it just seems a shame to see so many ups systems getting scrapped for the want of fresh batteries, when maybe a few guys could work together reverse engineering one

and altering it for inverter use.

anyone have any interest in forming a group to do this sort of thing?

more hands, more minds, should make for a quicker result?

bob g

[bob g]

no interest?

even if i have the schematics for many of the apc ups's?

(700, 1000, 1400, 2200, 3000, and 5000 smartups, amoung some others)

bob g

[jeffbirkle]

Hi all.

I have a 7.5KW Ferrups ups. 110AC, 220AC output, 110 volt DC battery bank input.

 I was really hoping to use this, It would be great, but the stand-by power is around 700 WATTS (OUCH). I could add some circuits to shut it off until a load is detected, but even so, a 100 watt fridge will still use the full 700 watt stand-by power. Unless I change/remove stuff that isn't needed to bring that stand-by down.

So I may have to sell it and by something else.

J

[SparWeb]

Okay, I'll bite.  Partly, at least.

I have collected several UPS's (APC Smartups) whose batteries were trashed but otherwise look okay.  Could you let me see the schematic of the APC 1000, even if it's solely for the purpose of checking if they still work or troubleshooting the ones that don't?

Sorry, no EE diploma nailed to my wall, so I won't have much to offer in that regard.

[scottsAI]

bob g,

I hope your not kidding, asked here if anybody had schematics... nope.

If you really do have schematics then I would be VERY interested in helping you meet your goals as long as I get a complete schematic for a unit above 1kw, 3kw best. Must be of the SmartUPS family.

With a schematic, a bit of rebuilding, a good chance we can convert UPS into an inverter or something more useful. Not that an UPS is not useful! I have 6 on line.

My goal: keep it as UPS (two day house backup), Whole house UPS, want standby current below 25watts. Four 3kw units have 200w standby... no go.

Have BSEE and designed/built power inverters. Does that work?-)

Please contact me, email address above. Skype: scottsai12

Scott Beversdorf.

[bob g]

i will email the schematic to you this evening

let me know what you think, i would expect maybe some differences

due to improvments made by the oem, but probably 98% the same for all

1000 series ups's made by apc.

bob g

[Hilltopgrange]

Hi Bob

       I would also be very interesed in this project! I have a matrix 5000 from APC it runs anything I throw at it but like the rest of them it sucks the life out of batteries on standby, 150w no load and thats with the inbuilt charger disabled. The matrix has 3 fans each 7w that run constant, I was considering fitting a snap disc stat so they only run when needed. I think the main problem is the huge transformer and all the switching gear for power conditoning etc. Im not sure I could contribute to the project as such as its not my field but I would be very interested in any progress. I to have searched the net for drawings and info on the matrix but info is very scarce. Would you by any chance have the drawing for a matrix? Keep us posted on any progress or if your starting a mailing list could you add me to it (hilltopgrange at tesco.net)

Regards Russell

[bob g]

Russell:

i have not come across schematics for the matrix or symmetra series

although i can't imagine they are vastly different in concept to their

smartups units.

few more bells and whistles, fans and such on the matrix

and the symmetra uses a modular approach, one logic drive and slide in

power units.

i can send you the smartups 5000 series schematics, maybe they would be useful

bob g

[scottsAI]

bob g,

Can you send me the schematic?

Thanks,

Scott.

[Hilltopgrange]

Hi bob that would be great thanks my email is hilltopgrange at tesco.net ( just replace the at) Many thanks again

Regards Russell