There are 3-#6 THHN and one # 10 THHN, EGC feeding from the 3 phase 208 disconnect with 3-100 amp fuses.What size the conductors feeding the 75 amp breaker? You need 100 amp or larger conductors on the load side of the bus duct disconnect and an EGC selected from T250.122 as Dennis stated.
The #6 conductors might be fine, particularly if there are motor loads, which in a CNC there probably is.There are 3-#6 THHN and one # 10 THHN, EGC feeding from the 3 phase 208 disconnect with 3-100 amp fuses.
I believe, there should be #3-THHN and one # 8 EGC , Because, 75 amps X 1.25 = 93.75 amps and the next higher OCPD is 100 amps.
the 75 amp disconnect (non- fused) is for the CNC machine from the manufacturer.
PLEASE, Correct me if I am wrong
thank you. for the information.