question

hananmcgrory avatar image

AC load data display conflicting with 2 x 10kva quattro in parallel

i have 2 x 10 kva quattro in parrallel

2 x fronius 8.2 and a mppt 150 / 85

bmv 702 and ccgx


Ac load data is incorrect in the home screen and in the menu

even the volts x amps does not = watts

screen shots attached

Ant thoughts

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MultiPlus Quattro Inverter Chargerparallel
download-17.png (38.9 KiB)
download-16.png (29.8 KiB)
download-15.png (39.1 KiB)
download-14.png (12.4 KiB)
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1 Answer
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @HananMcGrory,

Before I dig into this a bit, none of this should effect the safe and reliable operation of your system.


Your images uploaded at quite low resolution, it's difficult to see the details, So I will address the question generally. It's a fairly common question and also ties into some of the product limitations such as minimum AC input current limit.



The CTs inside the Multi that are reading the currents are not precise measurement equipment. They are functional and fit for their operational purpose. Any further diagnostics and analysis is made available to help with troubleshooting, and not intended for anything much more than that.

Further, the data that is read is not always perfectly timed with all the other values, so a single point in time might show a very large current supplying a very small load, and a few moments later a very small current is shown to be supplying a very large load. In average over time, these cancel each other out quite nicely, but just looking at any single moment in time can be quite confusing.

High quality test equipment (such as dedicated Fluke Multimeters with clamps) will have much finer resolution, smaller margins of error, increased refresh and sample rates, true RMS readings, and other features. These testers to take that more accurate reading can also cost as much a whole inverter.



Amps x Volts = Watts only applies for DC circuits, and pure AC resistive loads.

When talking about AC circuits you need to account for the power factor, when the AC circuit includes inductive and capacitive loads. These shift the phase of the voltage and current sine waves leading to reactive currents.

The current wave (and reading) might not align with the voltage wave.

There is good introduction here:

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-11/true-reactive-and-apparent-power/

And deeper explanation here:

https://www.electronics-tutorials.ws/accircuits/power-triangle.html


When you multiply several of these variably timed and functional but not precise variables together, it can make for some confusing results.


Note if you are seeing these values that are not adding up and dramatically unexplainable over a long period of time (i.e an hour or more), it is possible (and more likely when using AC PV), that there is a configuration issue, where one of the calculations or readings is being incorrectly inserted.

i.e A PV inverter is producing on an AC output, but the AC current clamp is not correctly configured for that size unit, and delivering to more of the AC load that it's reporting as it's output.

Or the CT reading for a PV inverter is connected after a load so not delivering an accurate reading.

Or a networking issues is causing a delay between the communications reporting of the AC PV inverters output, and the power delivery.

etc.

The easiest way to check this is to isolate the AC PV inverter (turn it off) and see if the figures begin to make more sense after an hour of operation, and then troubleshoot from there. VRM is very useful for this.

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HI Guy,

THanks for the reply.


Sorry the resolution on the photos is not great.

pv invreter numbers are generally fine

mppt numbers are fine

the bmv numbers are generally fine

but the loads figure on the home screen is always out.


so i look to the menu screen and what i see is


in the menu screen / in the quattro, ac output

voltage is 240 if current is 20 amps then watts will be 2400watts (not 4800 as you would ecpect

if voltage is 240 and current is 40 amps then then watts will be 4800 watts.(not 9600)

in all the other systems i watch those numbers are spot on and volts x amps = watts .figure

i can see from the bmv readings on the home screen that the amount going to batteires, matched the voltage and current in the quattro ac output screen but the watts figure is always half, and consequently the calculated figure on the home screen for ac loads is out


i swapped the master out for a new one , just to see, but the issue is stll there.

the system did not do it when there was only 1 quattro. then i upgraded to 2 after a few months, and then the second fronius 8.2 .


could it be ve bus cable from slave to master?, could it be an issue in the slave?

i have done the firmware in everything every time i troubleshoot out there.


The system works like a dream, in a refrigerated shipping container with aircon @ 20 degrees.

I need a theory to work with, seems like the power reading in the quattro is always half what is should be based on the ac current in the quatrtro whether it is inverting or charging.


Any thought appreciated, swapping out equipment gets old when it is 8 hours drive.


Hanan