[RE-wrenches] 208 3 phase Off Grid Inverter

[Michael Morningstar]

I believe that with the transformer scenario, you will still have a secondary output with a 120 degree phase angle. Stacked inverters don't like that. Don't ask me how I know . It's been almost twenty years since I've run into your exact situation, and I remember experimenting with both open delta and Scott-T transformers only to make that discovery. The web wasn't what it is now, so there may be something that wasn't presenting itself back then. Good Luck

 
On Mar 24, 2014, at 7:44 PM, Ray Walters wrot

> Hi All;
> 
> I'm exploring options for an off grid project with an existing 30 Kw Kohler wired for 208 vac 3 phase.  The generator runs some 8 hp air compressors, so rewiring it is not an option.  We're primarily interested in reducing gen run time from the current situation: 14 hrs/ day.
> So far, only the Outback VFX inverters seem capable of being wired in 208, 3 phase, but according to the manual they can only be stacked 1 inverter per leg. This limits the system to only 3 inverters total, or 10.8 kW.  I would like expandability beyond this.
> 1) are there any other inverters available that I'm over looking?
> 2) Should I consider a transformer to convert from 208 vac/3phase to 240 vac/ singe phase?
> 
> We're not going to even try to run the compressors, just the other single phase loads, mostly 120 vac, but we have a couple of small air conditioners, that are currently running on 208 single phase.  I believe they would run fine on 240 vac, as they have a name plate rating at 230 vac.
> 3) We may possibly run 2 separate 3 inverter stacks and only tie together at the battery, but otherwise they would not be connected. This seems inefficient, and would require some load balancing of the various inverters.
> 
> All help and discussion is greatly appreciated as always,
> 
> -- 
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer,
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
> 
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