I am trying to wrap my head around the target kV value.
Thermal limits set what you can get out of the motor, so i assume that it's required to keep max losses the same as in the original revolt motor. I think i can take care of the copper losses if the water cooling is successful - the magnets and eddy losses are what concerns me.
Power output is proportional to the rpms so if i can increase max rpms then power is increased the same amount.
I think that the limiting factors for using higher rpms are exponentially increasing eddy losses and the possibility of motor disintegration
Eddy current losses are proportional to rpm squared.
(edit, source:https://endless-sphere.com/forums/viewt ... p?p=240035
Eddy-current losses are also approximately proportional to the square of the lamination thickness
So.. Going from 0.5mm lamination to 0.3mm keeping same losses:
(Rated)Rpm0.5=3120 (guesstimation from where efficiency drops off in pic from Revolt motors below)
kV=85 is needed to get 5200rpms with my 72V system assuming loaded rpms are 85% of unloaded
The same goes for the magnet segmentation. dividing each pole into 5-7 segments will have a positive effect, should be possible to lower the losses and heating to between 25-50%.
I am also considering to make the motor 10-pole as it lowers the fundamental frequency by 40% (from 7x to 5x rpm). I found that recommended max frequency for 0.35mm lams is 400hz according to an application note for electric steels.
7pole pair is 5200/60*7=607Hz
5pole pair is 5200/60*5=433Hz
Max rpm to get 400Hz on 10poles is 4800. How the hell do the rc outrunners fit this recommendation? They don't..
I have seen some researched motors where 10 pole was slightly higher efficiency than 14 pole.
I wonder what the reason is for the popularity of 12slot14pole RC motors?
I guess it might give a slightly higher torque density than 10-pole but really don't know
I hope some of you can check my logic above, it's been a while since i was in school and it sure wasn't electric machines i studied