If I want to increase a brushless motor's N-m/A by 3.44 times and reduce it's kV by equal amounts, I would rewind it with 3.44 times more windings using the same total mass of copper. Pretty easy to understand.
But.....
I don't want to reduce current capacity that much. So let's say I want to double the copper mass as well as modify the N-m/A and kV ratings. Since I will effectively be increasing total power capacity of the motor I know I will have to increase the perm magnetism of the core. But what do I do with the windings? Is it inductance that determines the N-m/A and kV ratings? Or will 3.44x windings have the same effect regardless of what diameter of wire I use?
sounds like u are redesigning the motor.
increasing the copper mass also increases the copper volume, and changes the shape of the magnetic field.
you may also run into saturation problems (well not so much problems, but magnetic saturation limits torque density).
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Yep, that's why I'm increasing the permanent magnents. My question is about achieving the torque/amp to rpm/volt ratio change I want.
If you change the strength of the permanent magnets, then all of your math will be for nothing. In fact, you could achieve your goal by simply changing the strength of the magnets.
As for doubling the copper mass, there might actually be enough room to do that in some of the Chinese motors I have taken apart!
Rewinding the motor will not change it's power capacity. Kt goes up, but Kv goes down. Same power out.
Saturation would happen in the iron cores of the windings, not in the permanent magnets. It will happen at a certain flux density, irregardless of the nature of the windings. With more windings it will happen at a lower current than with fewer windings.
"Lines of flux cut per radian" is what determines Kt and Kv, not inductance. You will get the same effect using any gauge of wire, however using heavy gauge wire makes the motor more efficient.
Now what would happen if I increased winding length by 1.85 times and rotor circumfrence bt 1.85 times? Would that achieve the 3.44 increase in torque / A and reduction in RPM / volts? (1.85x1.85 = ~3.44)
I don't understand what you mean by increase the winding length. Do you mean using 1.85 times as many turns, or using a form 1.85 times as long to wind the coil on?
The first, increasing number of windings. My apologies, I can be vague at times.