Help in calculations

[kingbambina]

I have a 400V, 10kVA UPS that will be fed from a 480V panel through 15kVA, 480/400V delta/wye transformer. I just want to confirm my calculations. I will take the power from 25A breaker with a 3C 10mm² power cable to the transformer. From the transfomer I will run 3C 10mm² + 4mm² ground to 25A disconnect switch and lastly to the UPS. Is this good?
Thanks

 

[tom baker]

Please convert your wire sizes to AWG. Also we don’t use 400V systems

 

[kingbambina]

Please convert your wire sizes to AWG

10mm² is 8 AWG and 4mm² is 12 AWG

 

[ramsy]

I have a 400V, 10kVA UPS that will be fed from a 480V panel through 15kVA, 480/400V delta/wye transformer. I just want to confirm my calculations. I will take the power from 25A breaker with a 3C 10mm² power cable to the transformer. From the transfomer I will run 3C 10mm² + 4mm² ground to 25A disconnect switch and lastly to the UPS. Is this good?

Here is a similar 480/400v isolation xfmr

NEC Table 8 shows 10mm² is between 6-8 awg, more than enough for ~16A balanced 3-Phase load, Pf = 0.9
My home made calculator shows VD ~3% @ ~230 meters away for #8 awg, and #12 egc from Table 250.122.

 

[tom baker]

Suggestion: post in US units.

 

[Julius Right]

According to IEC 60364-5-52/2001 Table A.52-4 (52-C3) – Current-carrying capacities in amperes for methods of installation in table A.52-1 (52-B1) –PVC insulation/three loaded conductors/copper or aluminium –Conductor temperature: 70 °C/Ambient temperature: 30 °C in air, 20 °C in ground
Copper conductors in conduit underground 10 mm^2 52 A permissible. aluminum conductors 40 A.
Conductor resistance at 70 oC copper 0.002125 aluminum 0.003587 ohm/phase

 

[Besoeker3]

Suggestion: post in US units.

There is a UK Electricians Forum. He should go there.