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According to my reference material, a 30 HP, 208 volt 3 phase motor draws 88 amps. That's #4 copper for a load that size.
For the purpose of avoiding nuisance tripping during startup (inrush current), your breaker can be sized up to 220 amps. That's 250 of the full load current rating.
I should have said 250% of the full load current. Sorry about the typo.