The minimum size conductors needed to connect a three-phase generator to a fused disconnect switch are ___ AWG for a generator rated 90 kVA at 480 volts.

The minimum size conductors needed to connect a three-phase generator to a fused disconnect switch are ___ AWG for a generator rated 90 kVA at 480 volts.

• A. 1/0
• B. 1
• C. 2
• D. 3/0

Answer: (B)

Sizing the feeder conductors to a generator comes down to matching the conductor’s ampacity to the generator’s full-load current. First, find the generator’s full-load current: I = S / (√3 × V) = 90,000 VA / (√3 × 480 V) ≈ 108 A. Next, use the NEC ampacity tables (with the proper insulation temperature rating) to pick the smallest conductor that can carry at least about 108 A. In the common table used for this scenario, 1 AWG copper provides enough ampacity, while smaller sizes do not meet the requirement, and larger sizes would be more than needed. Therefore, the minimum conductor size is 1 AWG.

Sizing the feeder conductors to a generator comes down to matching the conductor’s ampacity to the generator’s full-load current. First, find the generator’s full-load current:

I = S / (√3 × V) = 90,000 VA / (√3 × 480 V) ≈ 108 A.

Next, use the NEC ampacity tables (with the proper insulation temperature rating) to pick the smallest conductor that can carry at least about 108 A. In the common table used for this scenario, 1 AWG copper provides enough ampacity, while smaller sizes do not meet the requirement, and larger sizes would be more than needed. Therefore, the minimum conductor size is 1 AWG.