paper: 4 CIM versus 6 CIM theoretical calculations

[GeeTwo]

Originally Posted by MichaelBick

One last important item to keep in mind is the main breaker. A high power drivetrain with a current limit pulls the maximum current for more time than an equivalent lower power drivetrain. Because the main breaker is heat triggered, it is sensitive to prolonged periods over the 120 amp breaker limit, and therefore high power drivetrains are more likely to blackout than lower power drivetrains.

I fully agree with the concern, though I would consider tripping the main breaker a blackout, not a brownout.

Yes, you can draw more than 220A for short durations. This does not change the primary conclusion of the original paper that 3 CIMs operated properly can provide greater mechanical power drawing from a given battery and condition. This is because the only conditions in which three motors run less efficiently than two is on the fast side of the peak of the efficiency curve, when operating near the free speed limit. In this domain, brownouts are not usually of concern. I would not use this paper as the last word in tuning a current limiting system, but I do consider it a valid argument for using a 6 CIM drive train over a 4 CIM drive train when the team's game strategy involves pushing battles or other high-current operation.

Alternately, 6 CIMs would allow you to gear the robot faster for a given application, preserving good startup acceleration while increasing top speed, or leave gearing alone, preserving top speed while increasing startup acceleration (in torque-limited drives). This would not be nearly as much of a difference as a shifting gearbox, but it would be simpler and less expensive.