What is the load in amps for a 3-phase 480V feeder supplying a load of 112.5 kVA?

What is the load in amps for a 3-phase 480V feeder supplying a load of 112.5 kVA?

• A. 135.32 A
• B. 120 A
• C. 150 A
• D. 180 A

Answer: (A)

In a three-phase system, the apparent power S relates to line current I and line-to-line voltage V by S = √3 × V × I. So the current is I = S / (√3 × V). Here, S is 112.5 kVA (112,500 VA) and V is 480 V. Compute √3 × V = 1.732 × 480 ≈ 831.36. Then I = 112,500 / 831.36 ≈ 135.32 A. So the feeder current is about 135 A. If you check the other values, they'd require different S (e.g., 150 A would need ~124.7 kVA, 120 A would need ~99.9 kVA, 180 A would need ~149.9 kVA), confirming that 135.32 A is the correct match for 112.5 kVA at 480 V.

In a three-phase system, the apparent power S relates to line current I and line-to-line voltage V by S = √3 × V × I. So the current is I = S / (√3 × V).

Here, S is 112.5 kVA (112,500 VA) and V is 480 V. Compute √3 × V = 1.732 × 480 ≈ 831.36. Then I = 112,500 / 831.36 ≈ 135.32 A.

So the feeder current is about 135 A. If you check the other values, they'd require different S (e.g., 150 A would need ~124.7 kVA, 120 A would need ~99.9 kVA, 180 A would need ~149.9 kVA), confirming that 135.32 A is the correct match for 112.5 kVA at 480 V.