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Ac coupling whit GTFX3048

Posted: Thu Jun 18, 2020 9:26 pm
by yamill20
Hi have a question

I have two GTFX3048 2009edition
How to connect micro inverter for acin to sell and support inverter to charge batteries

Re: Ac coupling whit GTFX3048

Posted: Fri Jun 19, 2020 4:41 am
by Mike Curran
AC coupling connects your grid-tie microinverters to the output, or ACout, of your battery-based inverter (in your case those GTFX's), not the AC in.

Those GTFX's are not well suited for using them in an AC coupling application because they don't have any built-in way of limiting charge current to your battery when the grid is down and your loads aren't using all the PV power coming in from your microinverters. Without this mechanism you run the very real risk of overcharging your battery, and it'll happen quickly, too.

At a minimum you would need an FNDC to closely monitor your system battery voltage and use its built-in auxiliary relay contact to open a power relay between your microinverters and your GTFX's when battery voltage is sensed to be going high from overcharging. Outback used to offer a remote-operated circuit breaker ("ROCB") for this purpose but have discontinued it in their newer inverters (Radian, Skybox) in favor of a frequency shifting technique that is more reliable than an ROCB. This app note ( since removed from OB's website) describes how the ROCB works: ... be8178511a

If that link doesn't work, try this:
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