240V split phase transformer sizing?

[Nuclear_Cookie]

Hello all.

So i have a question about sizing a split phase xfmer. I need to upsize it to swap in some larger ultrasonic generators. Currently i have a 480VAC to 240V phase to phase xfmer rated for 10KVA powering (4) 1200W ultrasonic generators. Currently our fuse sizing is follows, 30A FNQ-R class CC as Pri. protection, 30A breaker Sec. protection and 10A for each generator. Do I treat this as a Single phase transformer and use NEC450.3B and fuse table 240.6A? or is there a special setup I need to use for a proper calculation.

Well after some testing we need to upsize the generators to 2600W a piece. Real quick math is saying we are now at 10.4KVA for the generators alone (each one drawing 10.83A for 43.32A total) (excludes the two 5A 120V outlets for the computers) and the xfmer should be upsized to the 15KVA. I believe i can get away with a 63A breaker for the collective generator breaker and use 15A breakers for the individual generator breakers. For the Pri. side I believe I can go as large as a 70A, but i think a 45A would be fine since that should 150% of FLA for the xfmer.

Thanks everyone.

 

[augie47]

63A, you threwa European breaker in the mix
If I did my math correctly, you meet the requirements of 450.3

 

[Nuclear_Cookie]

@augie47

Yeah, it was the closest to 150% FLA of all 4 of our ultrasonic generators that was the same series breaker that we are currently running. Each one is 2600W @240V, so 10.83A calculated each, total is 43.32A, then at 150% it is 64.98A so a 63A is at 145% rated should be close enough worst case we can jump to next higher breaker series. Its a 1492-spm2DXXX series by AB if anyone was curious. The general rule of thumb i was taught for breaker/ fuse sizing is just do 150% FLA and get the breaker size closest to that, preferably the next size up. Of course i always consult the NEC to see if there are any special requirements.

The biggest confusion I had was if there was a special calc for split phase 240V or if it could be treated as a single phase set-up.

And thanks for the double check.