3 phase inverter

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electro7

Senior Member
Location
Northern CA, US
Occupation
Electrician, Solar and Electrical Contractor
Hi,

Ill be installing my first 3 phase inverter, actually 2 of them. The inverter specs say 25 amps per phase of output continuous current. I planned on installing a 3 pole 100 amp breaker per inverter (25 amps per phase x 1.25) and sizing the conductors for 100 amp ampacity. Am I looking at this right? I feel like I am missing something (and should probably know this).

If I am looking at it right, I am confused in that the inverter termination points say #6 AWG max.

Thanks for your help!
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The 25 amps per phase is almost certainly the per line current.
A 40A breaker is more than the 1.25 times the 25A rating. A 30A would be too small. That is per inverter if you do not combine them ahead of the breaker.
A 100A breaker will handle 100A on each of the three poles.
If the 25A is line to line (which would be common on a single phase inverter description) the the line current would be 1.732 times that if you connected three of the single phase inverters in a delta shape. But that is extremely unlikely!
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Your output circuits just need to be sized for 25Ax1.25 = 31.25A

You should be using a 35A 3-pole breaker for each inverter. Probably a special order from your supplier, but they do exist.

#8 wire would be sufficient in most circumstances.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Hi,

Ill be installing my first 3 phase inverter, actually 2 of them. The inverter specs say 25 amps per phase of output continuous current. I planned on installing a 3 pole 100 amp breaker per inverter (25 amps per phase x 1.25) and sizing the conductors for 100 amp ampacity. Am I looking at this right? I feel like I am missing something (and should probably know this).

If I am looking at it right, I am confused in that the inverter termination points say #6 AWG max.

Thanks for your help!

I have seen that "per phase" language on inverter specs before and I wish they wouldn't say that. It just confuses folks with limited three phase experience. It's 25A, period.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
What does the DC input current to the grid tie inverter have to do with the inverter output fusing?
We are not talking about a VFD here, are we?
 
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