crossbreak said:
another thing: put 2 motors in parallel. Kv does not change. Rm is divided in half. Km is increased by sqrt(2)=1.41, it increases by 41%
What does this mean? Are two motors capable of producing 41% more torque? Obviously not. Funny to see that sKm changes as Well
We could just say: A motor that has
double the Km, is capable of
4 times the torque. Just keep in mind that this a quadratic function. Still, it really bothers me that two same motors together have a different sKm than one alone
We could define sKm as the square-root of mass, then sKm would remain the same value for two same motors: sKm-> [Nm/√W/√M]
Another intersting topic is:
How can we now compare motors in a potential drive? We need to know something about the drive: minimum required torque, maximum weight and size, budget
now motors and reduction ratios could be compared, to gain the best efficiency. But what means best efficiency? Depending on the gearing, it will be better on hills (higher reduction ratio, lower I²R loss) then on the flats (higher reduction, higher parasitic loss). Maybe it would be useful to discuss this in a different thread, i just wanted to give an example here, since gearing influences Km as well
Example: Bafang BPM with 5:1 gearing (4.35 kg) and without it (2.0 kg), sorry i have no NoLoad figures at hand