PVfarmer
Senior Member
- Location
- Newport County, Rhode Island, USA
You might be on to something before even considering conversion between three phase and single phase, based on what OP said with :"100amps of 480/277 from solar", that alone is about 83 kVA, yet he says he already has a 75 kVA transformer. Something don't seem right already and I am not even experienced with PV applications.
ggunn said:This is getting way off the beam. Unless we are shown otherwise, the OP is talking about a 240/120V split (single) phase service. Talking about 240V high leg services just muddies the water; connection to such a service with a three phase inverter may or may not work, depending on whether or not the three phase inverter needs a neutral (if it does it cannot use the center tap as such and therefore would require an isolation transformer) and whether the transformer driving the high leg of the service can take the output of the inverter (it's typically a lot smaller than the transformer(s) driving the other two phases).
If he has a 240/120V split phase service, no transformer will allow him to interconnect a three phase inverter to it.
kwired-
Yep, like I said, not sure how to get 100A of any voltage from those inverter models, which are 12A, 24A, and 40A @ 480V.
A 75kVA step up (or down) xfmr would be the right size for two of the 33kW inverters or so, or 3 of the 20kW models.
ggunn-
Farms are the most common place for 240D center tapped service, that's why I mentioned it.
I personally think it would help if everyone called 240D center tapped "240/120V" and called split phase L-L-N "120/240V". But that doesn't seem to be a standard thing.
The POCO calls 3ph 480/277V and calls 1ph 277/480V in the documents, but then in emails 3ph gets referred to as 277/480V so you have to double check...it's weird.
Anyway, wouldn't using something like this for just one of the 12 amp/10kW/480V inverters sort of...work, but not be worth doing?
10kW is = to 10kVA, so if you wanted to get to 120V from 10kVA of 480V 3ph, going with that 10% thing, you'd have to use at least 100kVA of transformer- which would be silly, paying more for the xfmr than the inverter.
Distribution Transformer 112.5 kVA 480V Pri x 240 D/120 CT V Sec
If there was no PV involved, and you had 10kW max of 120V loads, you'd need 100kVA worth of service xfmr(s)- doesn't seem like there would be any difference when instead it's PV output to the grid, despite the grid being an "infinite" input.
Why pay a lot of $$ for a xfmr and only use 2 windings and 10% of its capacity?