Quote:
Originally Posted by vamfun
Bill,
We have smoked 3 motors, but they all have partial power still. I measured one with a 4.5 volt input and measured the torque. It scales to about a 45% torque of a new motor. So I suspect that we cooked some windings.
Will a burnt inductor possibly allow partial torque or is the motor a brick with this condition?
If we do have partial torque, then is is likely any repair can be effected?
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I'm pretty sure the internal part of the coil has shorted by burned insulation there. This is based on the high current observed by running my one attempt to repair a drive. I thought burned insulation would be more obvious by discoloration. My nose tells me something serious has happened to that motor.
I think overcurrent in the inductor has made its coating break down and might have been the source of the first noticed smoke. My current theory {pun noted} is that the motor failed in stages as more internal coil heating caused more insulation failure leading to more overcurrent in a vicious circle that eventually killed the inductor into open circuit failure. The circle ended but repairing with a new inductor, or a new wire in my case, will not restore the motor to original condition. It won't make it usable for practice either due to the suspected armature damage.
The partial torque you noted throws off the gearing calculations so any experiments you are trying mechanically will be skewed for a fresh motor. That is, you get your robot working well with a "repaired" motor, but changing to a new one inserts a different energy profile that effectively negates all your mechanical tweaking. In our earliest testing, I think we might have fallen prey to changing characteristics of partially disabled motors. That is, the first smoke only wounded the motor so we adjusted pole grabbing tension, for instance. As the motor became less and less capable, we thought there was fault in whatever adjustment we just made.
Bottom line {hate that term} I'll be playing with the gears from these motors, and maybe I'll try to compare the burned coils with a good armature, but the motors will never make it into even a testing robot.