[RE-wrenches] 208 3 phase Off Grid Inverter

[Kevin Pegg]

Hi Ray, 

I have several 3-phase off-grid inverter/battery/generator systems out there. 

- SMA Sunny Island is the best. Can scale to at least 180 kW, maybe more. Reliable & very solid. I have several sites going over 2 years without a single second of power outage. 
- Xantrex XW. It can work in a 3-ph config, but it's not as stable system. We have taken to preventatively rebooting the systems every 4 months and that helps a lot - at least the outage can be planned and on our terms. 
- Outback has had so many power quality nightmares I won't go there anymore. 
- I believe Magnum has a 3-ph option but haven't installed one yet. 

SMA inverters are more expensive. And they work very well. They also have a very good battery charging algorithm and integral gen start control. 

Kevin

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org]On Behalf Of Ray
Walters
Sent: March 24, 2014 6:44 PM
To: RE-wrenches
Subject: [RE-wrenches] 208 3 phase Off Grid Inverter


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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