Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, concerning a three-phase installation and kVA calculations, is answered by the ECA:
Brown - 285.92A
Black - 361.52A
Grey - 285.92A.
What I plan to do is work out the kVA based upon all three phases at 285.92A (+10% for future), and then work out the kVA for the extra 75.6A on the black phase (+10% for the future), then add the two kVA readings together - as so:
3 x 230V x 314.5A divided by 1000 = 217 kVA.
230v x 83.16A divided by 1000 = 19.1 kVA - giving me a total kVA for the installation of 236.1. Does this look OK?
Answer: I would add 10% for future load to the black phase, making it 398A. Then calculate kVA as follows: kVA = A x V x 1.73 divided by 1000kVA = 275.
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