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Don<br>
Tigo Modules basically MPPT the module. Now installing them on an
inverter that has MPPT sure does pose an interesting question. "Who
is going to win the fight". Tigo sweeps relatively fast so if you
had a really slow tracking inverter the Tigo's would likely win and
life would be ok. If you had an inverter that tracks real fast it
could be a battle. The fact the aurora failed in the early AM
confirms my thinking it is the battle of the MPPT.<br>
<br>
Ryan<br>
<br>
<br>
<div class="moz-cite-prefix">On 5/8/2013 1:38 AM,
<a class="moz-txt-link-abbreviated" href="mailto:don@energysolarnow.com">don@energysolarnow.com</a> wrote:<br>
</div>
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cite="mid:20130507223851.8b71096d7d88573c67c7101a41a0e3ba.f147282eee.wbe@email14.secureserver.net"
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<div>Hi all- While I have not had the failure problems noted
with microinverters, PowerOne inverters have recently given me
a big headache. Installed their 6kW model last November that
failed in a month. They replaced it under warranty, no problem
no reimbursement. Then the replacement failed in March. Again
replaced, no problem. But that's the problem-- there was no
indication from the inverter of why it failed. When the
replacement inverter that was installed in March failed in
April, they declared it out of warranty and made me pay nearly
$900 for repairs. This is less than 6 months from initial
installation. <br>
</div>
<div>All the failures occurred after rainy weather. This time I
bought megaohm meter and checked the wiring. There was a nick
in the insulation where a negative DC home run pulled around a
rail corner, with a small but noticable burn spot. This did
not show up with a standard meter check, but it did with the
megger and some watering from a hose. OK, so there is an
intermittent ground fault. With a transformer inverter that
would just be a blown fuse with a ground fault error message.
But it seems this inverter will self destruct with a ground
fault. No error message or any other indication that even
PowerOne would or could relate before sending 3 replacements.
</div>
<div>The Tigo monitors indicated that each inverter failure
happened at morning power-up, with minimal solar current. Oh,
and having Tigo monitors in the system but not on the one-line
drawing was PowerOne's nominal excuse for canceling their
warranty. They posted a document on their website dated March
10, right after the second failure, to the effect that when
using Tigo monitors you must disable the inverter MPPT scan so
they don't fight. But didn't tell me, or apparently their tech
staff....</div>
<div>The post-mortem on the last two inverters (performed well
after the replacements were sent) indicated over-current in
the IGBTs. So where is this lethal current coming from? There
are only two strings, one each into this dual channel
inverter. There is not enough solar current to kill it even
in broad daylight. But a morning power-up failure can only
mean some AC input surge current sneaks through the ground
fault and into the DC inputs. Sounds like a design flaw to
me... There should not be anything that can kill an inverter
other than over-voltage or over-current; and that would kill
it quick, not a month or months later after a rain.<br>
</div>
<div><br>
</div>
<div>Can anyone suggest a possible failure mechanism? Surely not
the dreaded electrolytic caps-- the inverter is mounted under
a dry eve.<br>
</div>
<div>In general, how are transformerless inverters protected
internally from external ground faults? </div>
<div>And the obvious question is: how could anyone trust a
company with this kind of warranty service?</div>
<div>Thanks</div>
<div>Don Barch</div>
<div>Energy Solar<br>
</div>
<div><br>
</div>
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<br>
Message: 13<br>
Date: Tue, 7 May 2013 09:03:13 -0600<br>
From: Troy Harvey <<a moz-do-not-send="true"
href="mailto:taharvey@heliocentric.org">taharvey@heliocentric.org</a>><br>
To: RE-wrenches <<a moz-do-not-send="true"
href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>><br>
Subject: [RE-wrenches] Dual Channel Inverters<br>
Message-ID: <<a moz-do-not-send="true"
href="mailto:1F568BAC-8D04-4E09-BC44-9090C147F0B5@heliocentric.org">1F568BAC-8D04-4E09-BC44-9090C147F0B5@heliocentric.org</a>><br>
Content-Type: text/plain; charset="windows-1252"<br>
<br>
Since we stopped using micro-inverters due to the high
failure rate, network problems, difficultly in replacement ?
I've been using the power-one inverters a bunch because the
dual channels solve most of tricky issues like different
roof aspects, shading, and uneven strings.<br>
<br>
However, they are limited to 6kW, which is only mid sized in
todays world. I'm constantly having to design 7-12k systems
in residential applications all the time. Any other dual
channel inverts of the market for 240VAC? I remember back a
few years ago that sharp had a 3-channel inverter. Doesn't
look like it is still around.<br>
<br>
thanks,<br>
<br>
Troy Harvey<br>
---------------------<br>
Principal Engineer<br>
Heliocentric<br>
801-453-9434<br>
<a moz-do-not-send="true"
href="mailto:taharvey@heliocentric.org">taharvey@heliocentric.org</a><br>
<br>
<br>
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