Adding three phase sub panel to Suburban garage

[Sincerd]

I've spent 32 years as a commercial/industrial electrician. This chart is absolute garbage. Whoever came up with those wire sizes is a complete fool.

The motor currents are quite a bit high for 480 3 phase and the wire sizes are way high.

For example, I've connected about 50 10HP motors to 480 3 phase. They are almost always somewhere between 11 and 15 amps. Unless they're a long way from the source, #12 is perfectly fine. The only way I'd use #4 is if the motor was more than 1,000' away.

It annoys me to no end that something this misleading gets published.........

Yeah that's 240 (not 480) and overestimated by 20%. $100 worth of wire isn't really going to affect me. But going bare minimum might if a future upgrade exceeds installed conductors. Definitely trying to stay away from 480 so those numbers don't apply to me.

It's from chat gpt, based off what I told it to do. I just wondered if it was right, for the circumstances I listed above.

 

[Sincerd]

The transformer is likely to supply control power to the machine. The motor is a 7.5 HP AC induction motor, by nature it is a delta start/delta run. The transformer may be at 120 'line voltage' OR 24 VAC the reason for the transformer is to use a 3 wire three phase delta power source. That plug 'may be' some work around the on-board trandformer. The 4 wire/5pin plug shown may just be what the shop had? The other possibility is someone added a 120 leg with neutral to power a DRO or other 120 device?

That makes sense. I'll update the post when my toe Jack gets here and I'm able to get the lathe on the pallet jack to moving on to the drop deck. Moving these things are real pain in the ***