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120A Main Breaker Thermal Analysis
Detailed thermal analysis of the standard 120A main breaker, especially addressing the question of whether or not there is any practical benefit from using canned compressed air to pre-cool the breaker before the start of a match.
The following analysis was the result of a discussion that ran from March to April of 2016, while various members of the Chief Delphi community debated the effect of using canned compressed air to pre-cool various parts of a robot before the start of a match.
We ran around in circles on the topic of using this method on a CIM motor; it would of course cause thermal stress and warping, which could in turn result in power loss due to demagnetization, and even a risk of catastrophic failure if repeated thermal shock cycling causes the ceramic magnets to shatter. At the same time, however, specific examples of these failures were hard to find; additionally, many teams had used the method without noticing any significant detrimental effect. Perhaps Al Skierkiewicz summed it up best: many teams won’t notice any negative effects from this method, but the practical benefit is also minimal.
Once that discussion wrapped up, the question remained of whether or not the same method would have any benefit if used on the standard 120A main breaker before the start of a match. With only one moving part (especially since that part’s entire purpose is to deform under thermal stress), might this be a better application of the canned-air cooling technique?
My original contribution to this discussion included an incorrect assumption about the series electrical resistance of this breaker, however, and so the resulting numbers were off by a factor of 6; since I can no longer edit that original post, this white paper includes a couple of corrections based on the responses I received, and everything seems to pass the sniff test now.
Main Breaker Thermal Analysis.docx (27.3 KB)