SMA 6.0 Inverter putting out over 6000 watts????

[Murby]

My system consists of an SMA 6.0 US inverter and 28 SolarWorld SW270 panels (7.56kw of panels)

We had a heck of a day today, we generated 44,640 watts of energy.. The real time meter was pegged at max almost all day with only a few minutes of clouds here and there.. I have a big Blue Spruce pine tree next to the array and we chopped it down today because it was shading 3 panels at the far end of the array in the morning.. One panel was almost completely shaded, the one below was around 1/2 shaded, and the one below that was about 1/4 shaded. It was dragging down the entire sub-array.. 12 panels on one MPPT channel were putting out the same power as 8 panels on another MPPT channel. but that's fixed now.

So I have some questions based on my observations. When I go into my inverter settings, its maximum output power is set at 6050 watts.. (on a 6000 watt inverter?) This came from the factory this way.. Is that normal?

What even more strange is that when I added up the numbers for DC power production, it came to 6224 watts and my inverter was cranking out 6092 watts. Huh? I thought the inverter would cap it at 6kw and not a penny more.. What's interesting that when my panels are under full sun, the inverter is always pegged at some number above 6000.. The more the panels generate, the higher the output of the inverter goes. Is it normal for these inverters to let a bit of extra power through like this?

I'm worried about what's going to happen in late May when the panels start cranking out 7000 watts or more... My array is set at 33 degrees so its not at a perfect angle for this time of year...



SMA Output.jpg

[max2k]

My system consists of an SMA 6.0 US inverter and 28 SolarWorld SW270 panels (7.56kw of panels)

...
So I have some questions based on my observations. When I go into my inverter settings, its maximum output power is set at 6050 watts.. (on a 6000 watt inverter?) This came from the factory this way.. Is that normal?

What even more strange is that when I added up the numbers for DC power production, it came to 6224 watts and my inverter was cranking out 6092 watts. Huh? I thought the inverter would cap it at 6kw and not a penny more.. What's interesting that when my panels are under full sun, the inverter is always pegged at some number above 6000.. The more the panels generate, the higher the output of the inverter goes. Is it normal for these inverters to let a bit of extra power through like this?

...

you're falling prey of digital value presentation - if you had needle gauge to show output power you would never noticed the difference as it is within 2% of the stated spec. Your inverter was already clipping so everything is as it is supposed to be and will look similar in May.

[AzRoute66]

Congrats. Inverter Efficiency is defined as AC Power / DC Power and yours was running at 6092W / 6224W = 97.9%. Very nice.

Agree with max2k. Your AC output is within 1.6% of rated power. Who could ask for anything more?

May/June should be more of the same with longer days.

I don't know squat about inverters, but if I've pieced together some of the stuff I've overheard correctly, they almost all will do WELL over their rated power for periods of time ranging to a few minutes to even 30 minutes, depending on the surge size/type. That tiny overage you see isn't surge, just mentioning it as a possibility when loads kick in.

[Murby]

I think you guys are missing my point.. I'm not worried about my inverter's conversion efficiency, My point was that my 6000 watt inverter is putting out MORE than 6000 watts and it seems the more my panels generate OVER 6kw, the more the inverter generates OVER 6kw.. the same inverter that's only rated for 6000 watts! Kind of worried about heat buildup...

AzRoute66, this is not a battery inverter we're talking about that's dealing with load surges like motors starting up.. . this is a grid tie solar panel inverter that is converting DC power directly from the panels and feeding it to the grid.

Anyhow.. I was just worried that maybe some throttle governor wasn't doing its job or something..

[sensij]

It is definitely clipping, so no worries about going higher than you've already seen. What are you using to measure the output, the inverter itself? It is probably not calibrated as well as you think. Put a revenue grade meter on there and it might tell a different story.

[max2k]

I think you guys are missing my point.. I'm not worried about my inverter's conversion efficiency,

I didn't say mention conversion efficiency. I said your inverter power output was approximately 102% which is within 2% off 100%. Inverter's main purpose is to convert DC to AC and not to measure its output to a fraction of percent accuracy. As sensij pointed out it can even overstate the power you're producing so I wouldn't worry about it.

Anyhow.. I was just worried that maybe some throttle governor wasn't doing its job or something..

so 2% over which might not be even the case got you worried but lower100% didn't? You need to work on your worries Everything is fine there, it is made with far bigger tolerance than few percent extra power: say you got heat wave and your amb temp increased by 20 deg. That would make its life much harder than 2%. It will still survive up to its rated ambient temperature and then some- engineers designing these things always add some extra cooling capacity.

[Murby]

Thanks for the replies everyone! Good info.. Good to know.

[AzRoute66]

AzRoute66, this is not a battery inverter we're talking about that's dealing with load surges like motors starting up.. . this is a grid tie solar panel inverter that is converting DC power directly from the panels and feeding it to the grid.

Anyhow.. I was just worried that maybe some throttle governor wasn't doing its job or something..

Could be one of the throttle governors, better check them all - and I see your point about no load surges on a grid tie solar panel inverter. How silly of me.

[Murby]

Could be one of the throttle governors, better check them all - and I see your point about no load surges on a grid tie solar panel inverter. How silly of me.

I detect some sarcasm? Throttle governor is the best I could come up with on my first cup of coffee... give me a break..

[ButchDeal]

I think you guys are missing my point.. I'm not worried about my inverter's conversion efficiency, My point was that my 6000 watt inverter is putting out MORE than 6000 watts and it seems the more my panels generate OVER 6kw, the more the inverter generates OVER 6kw.. the same inverter that's only rated for 6000 watts! Kind of worried about heat buildup

Have you looked at the spec sheet for the inverter you have? They are rarely exactly on a whole kw. In ant case unless you have a revenue grade meter, it is unlikely that either the D.C. Or AC readings you have are highly accurate, likely as mush as 2% off.

[Mike90250]

I see a flat top on your graph, and that looks pretty darn close to 6Kw for me. The flat top indicates that the inverter IS maxed out and limiting power.

What if the rounding error went the other way, and you only got 5,968 watts ???

[Murby]

I see a flat top on your graph, and that looks pretty darn close to 6Kw for me. The flat top indicates that the inverter IS maxed out and limiting power.

What if the rounding error went the other way, and you only got 5,968 watts ???

Inside the inverter parameter settings, its factory set to limit output to 6050 watts... and that's where it hangs out most of the time. I have 7.56 KW of panels hooked up and the DC "instant values" menu will say they are producing 6100 or higher frequently.. Most of the time, if the panels are producing under 6200 watts, the inverter will max out at 6049 or some number really close to that... but when the panels start producing over 6220 watts, the inverter seems to let another 20 or 30 watts through... I've actually seen it close to 6100 watts output.
And yes, I'm just reading the power meter on the SMA interface wireless network.

I'm not complaining.. was just a bit worried as this is all new to me and double checking that what I'm seeing is run-of-the-mill stuff..

Thanks for the replies! very helpful and informative...