Motor Start-up with Encoder vs w/o encoder

Support Motor controllers/drivers and motors
1

Hi,

I have two motors that are the same, except one has the encoder and one does not 25DLx67L & 25Dx54L). The one with the encoder does not start due to an over current shut down from the MCD. It looks like there is a cap on the motor input on the version with the encoder. Removing the cap solves the current spike problem. Note: the encoder is not connected and not being used.
Anyone else come across this problem?
Do you know why this cap is on the motor input in the first place?

thanks

2

Hi.

I deleted your duplicate post in the sensors category.

The capacitor is for spark noise suppression. This app note has more details. It is normal for the capacitor to cause a higher draw when the motor is started, and it should be fine to use the motor without the capacitor if the noise is not a problem for your system. Before removing the capacitor, did it run when connected directly to power? What driver are you using?

-Claire

3

Thank-you for the response. If I apply a fixed DC voltage there is no problem to start the motor, the issue occurs when I use a PWM signal as one of the inputs. In this case there are current spikes on top of the main current ramp, these spikes trip the OCP of the device. It is possible to prevent the problem by lowering the initial PWM duty cycle but we wanted to avoid this additional control step if possible.