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 Topic Title: kVA - Amps, Three phase - Formula Topic Summary: Created On: 02 October 2013 09:06 AM Status: Read Only Linear : Threading : Single : Branch
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 02 October 2013 09:06 AM paultrimble Posts: 20 Joined: 22 March 2008 Hi all I have been asked to advise on supply conductor size for a sub distribution supply. The power I have been told is 10kVA, 400V. I am used working with Kw power but not really for kVA. Can someone clarify if my formula is correct please? I(A) = 1000 × S(kVA) / (?3 × VL-L(V) ) Therefore - 1000 x 10kVA = 100000 / (1.732 x 210V) = 27.49Amps? This is where I get a little confused, if I transpose kVA to KW my result is different ; - P(kW) = S(kVA) × PF 10*0.95 = 9.5kW Therefore using formula for 400V kW - Amps I get 14.43Amps? Hopefully that's not to confusing, Cheers Paul 02 October 2013 09:07 AM paultrimble Posts: 20 Joined: 22 March 2008 Just noticed a typo - 10000 not 100000 02 October 2013 09:59 AM AJJewsbury Posts: 16302 Joined: 13 August 2003 As a sanity check, I tend to think about it the other way around - 10kVA from a 400/230V 3-phase supply is the same as three 3.33 kVA single phase loads - so 14.49A per phase (at 230V). - Andy. 02 October 2013 10:03 AM paultrimble Posts: 20 Joined: 22 March 2008 Cheers Andy, I noticed I used 210 line voltage instead of 400V for some daft reason Your reasoning makes perfect sense 02 October 2013 11:04 AM Parsley Posts: 1359 Joined: 04 November 2004 I divide KVA/692 if using 400V (1.73 x 400) and by 718 (1.73x 415)for 415V to get current. 10000/692 =14.45A Regards
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