Getting the parameters right for controlling a BLDC motor.

Thread Starter

Øivind Bakke

Joined Aug 22, 2017

I'm currently working on a software for controlling a BLDC motor (FOC). Everything is working good so far, except the back-EMF-compensation. I believe the reason for that, is because I got my motor parameters wrong. The motor I'm controlling is DB42M01, a delta-connected BLDC motor from Nanotec. In their data sheet, they give me the phase to phase inductivity (2.6mH) and the voltage constant (0.0043V/rpm). The formula I use for compensating the back-EMF is as follows:
where L_q, L_d,i_q and i_d are the inductivity and current in the field oriented coordinate system, psi_p is the field flux and w_el the electric velocity(rad/s).

So, my question is, how can I convert the given data to fit my formula? Or even better, how can I compensate the back-EMF using these data directly?

Thanks in advance!

Side note:
I've converted my voltage constant to field flux by multiplying it with (60/2*pi) based on some notes I had laying around. It gives me the right unit(Vs), but I have no solid source to base this conversion on, and have no clue if its correct or not.