G2 18v22 Current Ripple / Inductance

Support Motor controllers/drivers and motors
1

Hello,

I am using the Pololu G2 18v22 motor driver to drive two high-quality motors. Recently, one of these motors started exhibiting an issue where it won’t output a torque when it is at a certain, repeatable position. At this position, the current draw is 0 and the resistance between the terminals is infinite. I am investigating overheating due to excessive current ripple as a potential cause of the damage. (Also it is possible that the motor was damaged for some reason other than overheating - if anyone has seen this sort of failure before I’d be interested in investigating other potential causes.)

Does the G2 18v22 contain any inductors or other mechanism to help reduce current ripple? If not, can anyone provide advice on implementing simple modifications, either to the motor driver or circuit?

For reference, I am using DC brushed motors from Maxon with a rated nominal voltage of 12V, continuous current of 6A, 0.108 Ohms terminal resistance, and 0.0336mH (0.0000336H) terminal inductance. Additionally, I had been driving the motors with a PWM frequency of 8 kHz (which I plan to increase after reading about PWM-induced current ripple).

Thanks for the help!

2

Hi.

It sounds like the brushes or commutator of your motor might be damaged causing it to not make good contact at a certain angle. That kind of damage could be caused by over current or overheating particularly if it was ever stalled for a long period or if it often switches directions quickly.

The G2 high-power motor drivers do not have any extra inductance on their motor outputs, they generally rely on the inductance to the motor to smooth out the PWM signal. If you are concerned about current ripple, I recommend increasing the PWM frequency like you mentioned. If that is not enough adding a choke might help.

-Claire