Quote:
Originally Posted by Torbots 1197
The motor we pulled the photographed inductor from did not smell burned nor did it have any visual release of "magic smoke". We have noticed with some other motors that even though some magic smoke was released they continued to run but at a degrated level. Some guesses within our shop is that some of the inductor's windings fused together, allowing current to still flow through the motor.
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Your report just adds to the mystery of the smoke. Here is my current theory about the failure of Tetrix motors. These motors have no ventilation or builtin fan cooling. Over current in the armature coils can cause them to overheat. Do this often enough and the shellac (like) insulation will melt (and smoke) in places and short some wires together. This will lower the impedance of the coil and increase its current demand. That is, the motor still runs, but uses more current to do it. More current means more possibility of insulation melting and shorting. Eventually so much current is required by the motor, that the inductor can no longer pass it without failure by overheating.
I suspect that the smoke in your case came from the armature and that your motor is still usable even though degraded as you report. Melting insulation does not necessarily cause windings to short every time. It is just that you cannot continue to melt insulation without consequence for very long. The difficulties we're having with this motor are not mirrored by the way they are used in the FTC because the FTC is using them via motor controllers with electronics. Perhaps the GDC envisioned more robot-like minibots climbing those poles with more electronics than is common in this year's machines. I think that would have been kinder to the motors, at least.