i was thinking the circular mills was related to cable ampacity, but you are saying the cicular mills calculation is to make sure the slot gets filled. OK, got it :)

i suppose the ampacity sort of works itself out because we chose the largest gauge wire we can wind with by hand (#18) and then the motor/slots are only so big it self limits to the cooling capability of the motor anyway. that is, if the slots were bigger/deeper/longer perhaps we could fit more copper and ampacity would increase.. but so too would the physical size of the motor. in reality, the size of the motor & slots is fixed, so the power is fixed, we just fill the slots with copper as they exist, but in such a way in accordance with your math & instruction (to get lower voltage & higher current operation).

ps, the reason i was asking is because i am wondering what the current rating needs to be for the MOSFET inside my DIY controller. its funny, the blocking voltage rating of the mosfet is the same no matter how the motor is connected becasue the DC bus voltage will not change, only the current rating. so, theoretically, for delta connected motor, the voltage rating is the same but the current rating is higher which of course costs more $.. but you get more torque so.. now we see how it is not free. nothing is for free in engineering, always a trade off!

just an update, to be more clear.. i am interested in determining the phase current in the cable feeding the motor, not the phase current in the motor winding (i think i was getting confused myself!). so following ivan's motor rewind instructions, we rewind to get lower voltage (higher current), same power. then we connect the windings in Delta. done. the impact on the controller is now the rated current of the mosfet must be higher:

**Iphase_cable = sqrt(3)*Iphase_motor_delta.**