Sorry, your calculation is not wrong, bad wordings (as usual) on my end, excuse my English.
Then you have 277v*280a * 3 * 0.8, that's roughly 185kw in total, but you have bigger problems to worry about, most mining gears won't work on 277 volts, IIRC someone mention 255v was good on some T17 but not all, I think most folks who have 277v use Microbt gears, of course, not all Microbt gears support 277v but they do have a few options like the models that use p21 PSU, I had this voltage conversation like a year ago, and I am a bit too old and my memory isn't so great, so take the voltage info with a spoon of salt and do more research in that regards.