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Question on: Fronius inverter behaviour on low power

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Posted by Christian Kaiser on May 16, 2006, 7:25 pm
 
Hi,

my IG40 inverter behaves a bit strange when the PV modules supply too
little power (usually in the evening when the sun is gone):

When the power gets less than 11 W, the inverter starts a loop of
"StartUp", "<10 W", "Start ENS", "PowerLow" and other states, only
ending when the power gets too low for even this. This might take
several minutes. As it also switches some relay, I'm not sure this is
really harmless for the inverter.

I would have expected a hysteresis, that the inverter would not try to
switch on again until the module's power is above a higher value than
the one where it switches off...

Fronius itself did not yet state anything about that, neither where it's
normal, nor on the fact if it harms the inverter. Only a personal
statement of a support worker there who says "as Fronius has a long
experience in research of welding equipment, I do not fear it will do
any harm".

Did anyone else who has a Fronius inverter observe something like this?

Christian

Posted by dold on May 16, 2006, 8:15 pm
 

I see exactly this behavior for about 15 minutes every night on my Fronius
IG-4000.  I don't know that I've heard any relay switching, and if I did, I
wouldn't worry about even 10 cycles of a relay per day over the life of the
unit.

Someone pointed out that it is drawing some power from the grid while it is
doing this routine, and that is wasteful.  It should probably shut off and
stay off, as you said, until some higher level of PV energy is seen.

--
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Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5

Posted by Christian Kaiser on May 17, 2006, 10:18 am
 Thank you.

Why does Fronius not just say "yes, this behaviour is normal" then (or
better yet, get rid of it).

If it consumes the power from the PV cells, it does not matter. If it does
from the public power net, I think the energy providers would care, as this
current is not counted by the counters that measure my electric input into
the public net.

Christian



Posted by dold on May 17, 2006, 8:35 pm
 
It would seem that it is power from the PV.  That would explain why it
eventually fails.  If it were from the grid, as the other poster suggested,
it would be measured, unless your connection is different from mine.  My
Fronius ties to a normal circuit breaker in the existing power panel.  The
meter tracking power in and out of my premises would have no distinction
between the Fronius drawing power (which it does if you ahve a datacom
card, which uses power 24/7), or any other device in the house.


Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5

Posted by Christian Kaiser on May 21, 2006, 6:46 pm
 Well we have _two_ different meters - one for power consumption, and one
for the enery we give to the public grid.

This is important here in Germany as we get much more money for the
energy we produce with our PV cells than the energy than we consume from
the grid.

Christian



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