Question regarding SMT750I

[BillP]

Hello, i own this UPS for quite some time and everything seems to be working fine, except when AVR Boost kicks in... i checked the screen on the UPS itself and found out:

input around ~205V (may fluctuate by -+8)

output 245V

Is not it getting too high? considering the nominal voltage is 230V, why is it boosting that much?

[BillP]

Hi again,

I will go back to our EMEA support because I did not hear back. I apologize.

I couldn't find what reference you were asking about as far as the projector - could you clarify? Was it if your projector would have a problem with it or..?

I can clarify for you but I want to make sure I answer the right question for you

[BillP]

Yes, in my last post i mentioned:

The only thing i have connected to this ups is a projector, specs says 100V to 240V, so while it seems to be ok up to 240V, reaching 245V, i'm not sure it may end up doing any damage?

[BillP]

Ahh, sorry! I focused on page 1 replies of the thread.

I think 245V will be fine. That is usually what it is rated for so if you fed it 240V, let's say in North America (since we use 208/240V here), then it is nominal 240V and likely will be OK with around 250V.

I am telling you based on my experience with equipment in general. You could always just triple check with the vendor might I imagine the power supply in the projector would turn off if the voltage was too high or too low.

[BillP]

Let's start here - what is the nominal (normal) voltage you should be using in your region for your attached equipment to the UPS? Is it 230V?

[BillP]

Ok. I had to sit down and think about this a bit and discuss with someone else to help me understand better.

The goal of the UPS is to output voltage within +/-6% of the rated output voltage (thus, 230V by what you have set now). If it can't do that, then, it is supposed to be boosting ~12% or ~24%. Then it does that behavior I noted earlier. I am assuming you see 245V at the highest - is this when the input is under 200V?

Either way, I think we may see a more applicable and expected behavior for your scenario (and closer to 230V) actually if you set the output to 220V or at least it should not boost it so high.

[BillP]

Yes, 230V.

[BillP]

Nope, at the moment i was checking, definitely was not under 200V, thats because it made me worry... Since it's not happening very often, i'll keep closer attention next time it does and report back..

Meanwhile, could this be a bad calibration from factory? bad unit?... I may try what you suggest, but i consider that it should be 230V as thats what my region uses...

[BillP]

Can you measure the AC voltage with a voltmeter to see if there is a huge difference in voltage measurement? I doubt there is an issue here based on what we've discussed, we just need to understand the behavior and logic behind it.

If 230V is the norm, why is your voltage typically ~205V? Or was that just temporary for an our or two? I was sort of thinking you had a constant low voltage condition there but you said it does not happen often.

I think majority of equipment, especially IT equipment, would be rated to 250V. If the UPS is set to 230V, there is no way the UPS would allow an unacceptable output voltage to the equipment - so that is why you can also adjust those transfer voltage ranges to determine when the UPS uses automatic voltage regulation or even goes to battery operation instead. So, for majority of equipment, the UPS would go to battery prior to allowing harmful voltage through.

[BillP]

Sorry i dont have any voltmeter, but i do have another ups right there in the same room, a BACK-UPS PRO and while it is a different model, readings for the incoming are the same, but in this last one, when avr boost kicks in, incoming 209V output 234V, now this makes sense (+12%) and should be what the smartups do...

Right now, on the smartups incoming voltage is 209V and the output is 243V.

I tryed your suggestion, output to 220V and result was the same, identical voltage readings.

Only thing that made a change while on output 220V is that now, while ONBATTERY (done the test by disconnecting the unit from the wall) outputs 220V instead of 230V...

[BillP]

Can you get me the event and data logs from PCBE? I will have to have those reviewed and figure out why the UPS is not stopping the double boost.

And since you changed your output to 220V, can you let me know if your transfer points also changed?

Also, I forget, just incase I need it, can you get me the firmware version of the UPS - should be something like UPS 09.0 or similar.

[BillP]

Logs are from just today, as prior to discover this i never attached the unit to a pc... Anyway, i will left pc on to gather more in case it's needed.

No, i believe transfer points did not change, will double check later..

Firmware SAI 1: UPS 08.3

Firmware SAI 2: MCU 14.0

Firmware SAI 3: UBL 08.5

Firmware SAI 4: MBL 14.0

[BillP]

Thank you for the logs.

So from what we can see in the logs you do have, it appears we may have an issue with hysteresis and then it also appears the UPS is boosting the voltage more like 15-16% rather than 12% (comparing an input of 211 to output of 243, for example) - I will check with EMEA support to see if this is normal - I was assuming this UPS would operate like an SMT750 which we use here in the US and I can't think of a reason why the SMT750I would use a different boost voltage but I better verify

On the hysteresis, I think there is also a 3-5 voltage value for that where the voltage change 3-5V before boost (or trim) would toggle on/off as to not have a constant scenario of on/off/on/off/on/off.

[BillP]

While we investigate the specification around the % for boosting/trimming, the suggestion I keep receiving is to lower the low transfer point to something like 200VAC or even a little lower so there is no way to receive more than something closer to 230V. Or, just leave it the way it is. As I said, assuming this is standard IT equipment, it should run off of anywhere from 200-250VAC typically but you'd want to verify it is not something like a PC we're dealing with here.

I am still waiting to see what we can find out about the boost on this unit to be sure, I just need to wait on EMEA to report back. They did also see about 15% boost in their testing when I asked.

[BillP]

Here are updated logs, with more data just in case they want to take a look..

Ok, i'll try to lower the transfer point to 200 and see what happens...

The only thing i have connected to this ups is a projector, specs says 100V to 240V, so while it seems to be ok up to 240V, reaching 245V, i'm not sure it may end up doing any damage?

[BillP]

Hello, i own this UPS for quite some time and everything seems to be working fine, except when AVR Boost kicks in... i checked the screen on the UPS itself and found out:

input around ~205V (may fluctuate by -+8)

output 245V

Is not it getting too high? considering the nominal voltage is 230V, why is it boosting that much?

[BillP]

Hello,

I was looking in the user's guide (http://www.apcmedia.com/salestools/SCON-7NBSEM/SCON-7NBSEM_R6_EN.pdf) and for 230V models, you can actually adjust the output voltage it appears to 220V, 230V, 240V.

Can you confirm what you have it set to, maybe 240V? Maybe we should adjust that output voltage?

I assume you can check it via the front LCD panel.

[BillP]

Yes, already looked for this option, but it's not available on the lcd, quite strange... maybe there is a combination of keys that need to be pressed on the startup in order to access it??

Only i could  find was this on PBE software, though i feel it's related to the on battery settings... greyed out:

[BillP]

Oh I just double checked and was reminded that in order to change the output voltage, the output must be turned off and then you'd see the output voltage be an available setting to be modified. Perhaps this is why it is not visible via the LCD too but definitely why via PCBE screenshot you gave.

But, I did a little search and 230VAC setting is likely fine assuming that's really want you want for a nominal output.

Here is how this UPS model works - You set your low transfer point to xxxVAC (as seen in PCBE). If the voltage drops below that xxxVAC low transfer point, it boosts it ~12%. If the voltage continues to drop and even with ~12% boost it cannot stay over xxxVAC, it boosts it by ~24%. If with ~24% boost it is still unable to keep it over xxxVAC, the unit goes to battery.

Thus, perhaps adjusting that low transfer point a bit will help this but it is likely your UPS is boosting ~24% rather than ~12%.

[BillP · Accepted solution]

Ok, i just checked and yes, with output off, the option appears on the lcd, it was indeed at 230V.

What is the voltage it try to stay within? low transfer point 208V or the nominal voltage 230V?

Because if it is the low transfer point, does not makes sense, as the voltage mentioned on the first post, was 205V, with a boost of 12% it's well over 208V, so what is the point of 24%?