Author Topic: Need advice choosing GTI string voltage  (Read 550 times)

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Offline lighthunter

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Need advice choosing GTI string voltage
« on: April 17, 2016, 08:20:50 AM »
Hi All, I want to know if there is a connection between the longevity of
solar inverters and the input voltage range chosen. The nameplate rating is
obviously the starting point but then the mfr. wrote that and generally arent
responsible for its replacement. Then again maybe none of you have ever had
one of these fail? It has just been my experience that the higher the voltage a.
semiconductor is exposed to, the more likely failure will occur, or do they.
generally spec these things so thats not a concern.

Right now I'm using mine at 250-275vdc mpv range and wondering if.
lifespan will change from 15yrs to 1yr if i run it at 400dc mpv.

Any of your thoughts or experiences are appreciated. Or reference to a
"lesson learned" thread

Thanks in advance!
cheers, LH
LH

Offline lighthunter

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Re: Need advice choosing GTI string voltage
« Reply #1 on: April 18, 2016, 08:49:39 PM »
Is a "solar laminate" the same product as a "frameless solar panel"?

I bought 4 of em and wondering how best to frame. I suppose silicone to some.
C channel aluminum?

Cheers, LH
LH

Offline lighthunter

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Re: Need advice choosing GTI string voltage
« Reply #2 on: April 25, 2016, 06:57:58 AM »
Feel like I'm talking to myself here ;D Just in case someone else wants to know this information (post title) I took my 2 string HF Grid tie inverter apart and measured voltages. With 250v pv coming in at 900w the first stage is a boost converter running input up to 404v. The second stage is an isolation HF xfmr stage, looks like 1:1 voltage conversion because it was 404v on its output side. The third stage makes the pure sine 240v synced output.

I would assume many of these string inverters are similar because I was able to find this topology dscribed elsewhere on the net. Therefore since I was using 250V pv the unit probably wont suffer from high voltage exposure from panels at least up to 400. At the 400 point i would guess the boost converter will run at nearly 100% efficiency. The current in first stage will not increase by adding more panels in series  either. The isolation stage and output stages will have higher current but that would be the same using both inputs at lower voltage. This will allow me to use the full 3.5kw capacity on one string input without undue stress while leaving second string input for wind generator ;D.

LH
LH