Drivetrain Current Draw

I have a few questions regarding drivetrain current draw. First, what is the recommended range of “pushing” current that a drivetrain gearbox should experience? I’ve messed around with different reductions in JVN’s calculator and found that it is difficult to get this value under the 40 amps that the motor breakers are rated for, which brings me to my next question. Is it common/ok for these 40 amp breakers to trip and reset a few times during a match while being defended or pushing other robots?

I won’t comment on what an ideal pushing current is, I’ll leave that to someone more experienced than me. I will say however that it definitely doesn’t need to be under the 40a/motor continuous that the breakers are rated for. The 40 amp snap-action breakers we use are thermal breakers, meaning that they will not trip immediately in an overcurrent situation - take a look at the datasheet:

40a Snap-Action Breaker Datasheet

Even drawing 80 amps through one breaker (200% rated continuous) the breaker is guaranteed to not trip for at least one second. This means that if you get into a pushing match and draw ~60 amps per motor continuously, you can keep that up for several seconds before you trip your motor breakers.

If you have more than two motors per gearbox, another factor comes into play - the robot’s main breaker. With three motors per side, each drawing 60 amps, you’re putting a total load of 360 amps (300% rated continuous) on your main breaker from drivetrain alone, not including any other mechanisms on your bot. At 360 amps, according to the main breaker datasheet, you will trip your main breaker in between 5 and 10 seconds, possibly before the individual motor breakers trip - and unfortunately for your bot, the main breaker does not auto-reset, and your robot will be out for the match.


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