3 Phase Power - Unbalanced Loads 1

[7Eggyjla4]

Hypothetical Question...I have a delta wired three phase power panel with a series of single phase loads that total 100kVA phAB, 200kVA phBC, 300kva phCA. How do I determine the resultant 3 phase load and the equivalent generator needed to supply the panel? There was a rule of thumb method mentioned, but I'm not looking for the rule of thumb. I'm not certain that ?kVA is accurate or (?kVA)*(?3)/3 is correct either.

 

[rbulsara]

Total load is still the total load no matter how you devide it. So its 100+200+300-600kVA.

If the gen is delta connected, one of the the generator's phase still need to meet the highest load in a phase so its 300kVA at least. The generator will have equal rated windings so the rating of the generator you need to install is 3X300=900kVA.

If the generator is wye connected, if you do your math (wye feeding the delta load, refer to some basic text books on elect circuits), you would come up with 250, 150 and 200 kva in the three phases, still totaling 600kVA. The rating of the gen required becomes 250x3=750 kVA,





Rafiq Bulsara

http://www.srengineersct.com