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rasti avatar image
rasti asked

Maximum input current for SmartSolar MPPT RS 450|200 NOC / SOC ?

Hello,

I want to use a MPPT RS 450|200 with 4 trackers.

Tracker 1 : 8x385 W = 3080W, one single string, South 30° inclination

all voltages/currents within MPPT specification

Tracker 2 : 8x385 W = 3080W, one single string, South 30° inclination

all voltages/currents within MPPT specification

Tracker 3 : 9x205W = 1845W one single string, South 30° inclination

all voltages/currents within MPPT specification

Tracker 4: HERE COMES MY QUESTION !

I am planning to use a EAST-WEST-configuration with 2 parallel strings.

East string has 4x385W Modules, 30° inclination

West string has 4x385W Modules, 30° inclination

Here is the specification of the modules

ja-385w.jpg


The problem (?) is that the max. input current of the MPPT RS 450|200 tracker is near or above the current limit.

When I use the maximum current specified under SOC, current is too high

Impp=10.99A , 2*10.99A=21.91A => too much (?)

When I use the maximum currents specified under NOC, current is OK.

Impp=8.83A , 2*8.83 A=17.6A => OK (?)

I am located in South Germany.

Can I use this configuration or not ?

Regards
Ralf

mppt rsinput current
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3 Answers
wkirby avatar image
wkirby answered ·

Even STC is not really reliable. Values exceeding these STC parameters are possible under certain conditions like cloud edge effects.
I have seen 1.8kW coming out of my 1.5kW (STC) array during these brief moments. My MPPT is sized to cope with these excesses.

It would not be wise to exceed the limits of the device. Always design to stay inside the limits plus some margin for errors or events like cloud edge.

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mryoshii avatar image
mryoshii answered ·

I think it doesn't matter if you over panel the mppt.
The MPPT will not exceed its 200 A.

Correct me if I am wrong.

I myself use a 150/70 at 24 V and have a 2200 Wp array connected to it. The data sheet says PV rated power, 24 V 2000W

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wkirby avatar image wkirby ♦♦ commented ·
The concern here is the 20A limit of the PV input.
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mryoshii avatar image mryoshii wkirby ♦♦ commented ·

Isn't that also limited by the output?
So that the 21A cannot be achieved?
Or will the MPPT simply kill itself?

Where do you see the 20A? In the data sheet of my 150/70 it says:
Max. PV/short circuit current 2) 50 A (max. 30 A per MC4 connection)
Therefore, the one of the big one is of course even higher.

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rasti avatar image
rasti answered ·

here's a pvgis simulation result https://re.jrc.ec.europa.eu/pvg_tools/en/ of the irradiation for east and west oriented modules at my location in June (all other months have lower values)

east-west-irradiation-june.jpg

The irradiation of an East or West module never exceeds 920 W/m2 under clear sky conditions.

Around 9am when the East module has its maximum at 920 W/m2, the West module has less than 550 W/m2. Same thing in the afternoon when the West module has a maximum, the East module produces much less power.

I'd say that the mean irradiation power of East & West combined is below NOC conditions at any time . So the setup would be fine. Does this make sense ?



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