I'm trying to suppress EMF coming from a brushed DC motor that I am running. I've tried using 0.1uF capacitors across the motor leads as discussed here: https://www.pololu.com/docs/0J15/9.
It works great for reducing noise, but it makes the motor respond very differently to the same PWM power supply. Specifically, I'm running an L298 at 30kHz.
Before, I was getting my intended minimum RPM at around 50% duty cycle. The motor was also running very steadily with constant power.
With the capacitors, I am getting a much higher RPM at a lower duty cycle and I'm having trouble running the motor at a sufficiently RPM. Also, at a constant PWM, the motor will start up and gradually slow down a little bit.
Is there a better way to control noise? I can understand vaguely why a high pass filter might have issues with a high frequency PWM - but the motor lead capacitor approach and PWM both appear to be the standard in implementing small, brushed DC motors.