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Originally Posted by Lisa Huang
How can we prevent motors from overheating?
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Lisa,
You have a lot of good ideas here. The absolute best one is to make sure that the mechanical design is such that the motor is running in an efficient area of the motor curves. By designing your drive train to optimize power and speed you lower the electrical current and hence the heat caused by the excess electrical current. When the motors are run at these design speeds, the internal fan also is efficient enough to remove some of the excess heat. Adding external fans is the next best, but the tradeoffs are more weight and current demand. Heatsinks are also useful but only to the extent that they can effectively remove heat generated within the motor through conduction. In the case of the drill motor, the majority of heat is generated in the armature which is only connected to the case at the bearings and brushes. Fans can move air around the armature but heatsinks cannot.
I am not a big fan of the coolant spray idea used by some teams. The spray does produce a thermal shock on the metal parts of the motor and if you use enough, the metals change size (thermal contraction) and affect clearances inside the motor. The compounds used in the spray also tend to wash the lubricant out of the bearings. Finally, that nice white frost that occurs when you spray the motor is moisture from the air being frozen by the spray. As the frost melts that moisture may end up in your motor or other electronics where it can cause some real damage.