What is the minimum size of the EGC that needs to be installed between a 400-A safety switch and a 3Ø motor using three 250 kcmil conductors?

To determine the minimum size of the Equipment Grounding Conductor (EGC) that should be installed between a 400-A safety switch and a three-phase motor fed by three 250 kcmil conductors, the National Electrical Code (NEC) provides guidelines that must be followed.

The size of the EGC is primarily based on the largest ungrounded conductor in the circuit feeding the motor. In scenarios involving conductors that are 250 kcmil, the NEC has a specific table (Table 250.122) that outlines the appropriate EGC sizes based on the size of the overcurrent protection device or the largest ungrounded conductor used.

For conductors sized at 250 kcmil, the NEC specifies that the minimum size of the EGC should be proportional to the ampacity of these conductors. In this case, a 400-A safety switch typically has an associated EGC requirement that aligns with the conductor size and the current-carrying capacity.

According to Table 250.122, for feeders that are derived from conductors of this size, a grounding conductor size of 3 AWG (which corresponds to the '3' in the answer choices) should be used. This ensures the safety and effectiveness