Hello all,
I’m interested in using the Odrive S1 controller with a M8325s 100KV motor for a university senior project. We will be running it at a low speed at about 3.6 Nm of torque. I am trying to estimate the power draw of this operation, but I am calculating it to be low. The documentation lists Km = .44, and the linked wiki page shows that Km = torque/sqrt(power). Will the power draw at this torque really only be 67 Watts? Thanks in advance for any help!
Hi! Yes, this is correct. To back up this number, the M8325s has a phase resistance of 24mΩ (phase-neutral), and a torque constant of 0.083 Nm/A. Thus, 3.6 Nm requires 3.6/0.083=43.37A, which will be 43.37^2 * 3/2 * 0.024 = 67.7W (this is just P = I^2 R). This is assuming zero speed, of course.
The 3/2 in the above is to convert phase-neutral phase resistance to “overall” resistance, the best way to visualize it is with the current angle aligned to a phase like this:
