What is the minimum wire size (in AWG) required for a 3-phase, 4-wire feeder supplying 150 amperes?

To determine the minimum wire size required for a 3-phase, 4-wire feeder supplying 150 amperes, you can refer to the National Electrical Code (NEC) guidelines, particularly Table 310.16, which lists allowable ampacity for conductors based on their size, insulation type, and installation conditions.

For a 3-phase feeder carrying 150 amperes, it's essential to account for factors like the type of insulation and ambient temperature. Generally, copper wires are preferred for their conductivity, so the calculations may differ if aluminum is used instead.

In this case, according to NEC guidelines, a conductor size of 2/0 AWG copper wire is typically adequate for carrying 150 amperes under standard conditions. When selecting wire, it’s also prudent to consider any additional factors such as the length of the run, voltage drop, and specific installation conditions, which can lead to adjustments in wire size. However, for the purposes of this question, under normal installation conditions and requirements, 2/0 AWG is recognized as the suitable minimum wire size to ensure safe and efficient operation for a feeder with a 150 ampere load.