Question

Problem 2: A pump station is fed by a 2000 A, 480 V three-phase electrical service. The station runs two small motors, giving it a load profile of 350 kW with a 0.82 lagging PE. Determine the minimum allowed gauge of the service conductors. Feeder lines are aluminum, THW, contained within a raceway with an ambient temperature of 40 °C. State the specific article(s)/tables used to determine your answer. 13 55 The station is being expanded to include two new 15 HP. 92% efficient pumps, with PF = 0.82 lagging and a 20 kW lighting system at unity PF. If these loads 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-7/100

Answer 1

Given pump station is fed with 2000 A Us = 480V Pc = 350kw - PF = 0.82 we have line a current 1 (3NSster .. 350x103 roxyfox Loos 10.82) 4 20.9845 L-34-914 from NEC Table. At 40° Ambient temperature. It has a rotating Factor of 0.86. so the new ampacity is 35.2A owput power =15HP = 15x745.7=11185.5 watts efficiency = 90% e power xooo efficiency. - ip Power xooo IP power = olp power efficiency 511185.5x100 - 90 CS Scanned with ve power=12428.333 watts CamScanner

linea current In = 12422.333 53x480 Llos 10.62) - In=14.95 L-34.91 A lines current PC = 20 kW przi (i unity PF) . : I 3= PELOS (PF) Fiz xüsx Llos (PF) - 20x103 Lo r3xugo ::. 13 = 0 . . : The total current Isis given by I - It Is + I3 -u 20.98714.95+0 . I -435.93 A we have Ampacity of conductor was 35.28 but present capacity is 435.93A CS Scanned 50 It exceeds the capacity CamScanner