FRC Blogged: - Motor Controllers

[Mike Copioli]

Something to think about.

-The Victor has been around for over a decade.
-It has never had internal over current protection and it has not affected it's performance on the field.

With the few failures I have seen most are caused from metal debris shorting the tabs of the H-bridge FET's. Although Internal over current protection would help prevent this, I think an even better approach would be to take measures to prevent the metal debris from entering in the first place.

Another thing to consider is the resistance of the power path feeding the motor controller. Al pointed out the role 10 gauge wire plays in this. Another even bigger player is the resistance of the Wago connectors, the 40 amp breakers, the PD and the internal resistance of the battery. In total you are looking at around ~40 mohms of resistance at 25 degrees C. This number increases significantly as these components heat up. If you have a way to measure internal resistance of your battery try performing the test at the power leads of the motor controller(with the controller out of circuit). You will be surprised at the amount of resistance that is actually present.