Please Provide the answer in details. A machine shop is fed by a 300 kVA, 480 V

Question

Please Provide the answer in details.

A machine shop is fed by a 300 kVA, 480 V three-phase electrical service. The shop runs many small motors, giving it a load profile of 220 kW with a 0.72 lagging PF. Determine the minimum allowed gauge of the service conductors. Feeder line are aluminum, THW, contained within a raceway with an ambient temperature of 40 degree C. State the specific article(s)/ tables used to determine your answer. The shop owner would like to add three new 25 Hp, 85% efficient lathes, with PF = 0.78 lagging. If the lathes are added, will the current in the feeder exceed the rating of the service conductors? Explain and show all calculations. 1 ton of refrigeration = 3.517kW. COP = eta/100

Explanation / Answer

FOR OLD LOAD PROFILE LOAD KVA=300KVA VOLTAGE 3-PH=480      PF=0.72          i=s/(1.732*v)=36A

fOR NEW LOAD 25HP=25*0.746KW=18.65KW           

ADD THREEE 25HP LOAD i.e = 3*18.65=55.95kw                  i/p power=55.95/0.85=65.82kw         i=p/(1.732*v*0.78)=101A           so total load = 101+36=137A

so we are using 75sqmm cable for serving cable AL

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