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Is This Repairable?

Old 05-23-2022, 01:45 PM
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Default Is This Repairable?

Himax HC6330 Pro with front mount conversion kit installed.

I think a piece of metal got inside the can as there are light score marks on the magnets. At about 2/3 throttle the amps shot up from around 60 to over 95 and the motor started smoking. Can temp was around 255F. Subsequent static tests showed the motor running within normal specs. I pulled the motor out of the plane and upon inspection saw that besides the score marks on the magnets, this little white blob of something holding 2 bundles of winding together had split apart. I'm guessing it's some sort of silicone.

You have to look closely at the inside where the windings are.

Is that something that can be repaired, and where would I get that done?
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Old 05-25-2022, 07:28 AM
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Your motor took a beating, core/winding temperature was/is higher than 255 degrees rotor temperature. Winding wire lacquer has deteriorated
That white stuff looks as if it got spilled in production. In that case just leave it there, the coils don't move, no unbalance.
However, if it is the result from the overheating, what is it, and where did it come from?
Is it wire insulation lacquer? Or silicone for sure?
Do you see dark(er) locations in/on the coils?

If worse comes to worse you can rewind your motor, and end up with a more powerful or cooler running motor in the process

Nasty scenario
  • Overheating magnets causes de-magnetizing (irreversible! ), which in turn results in higher velocity konstant Kv. Motor wants to run faster, thus drawing more current and more power.
    Motorcurrent and -power drawn are proportional to velocity konstant Kv³ , resistance losses in the copperwire are proportional to current²
    Therefore resistance losses are proportional to Kv
  • Higher current → hotter motor → weaker magnets → higher Kv → higher current → hotter motor → weaker magnets → higher Kv → higher current ⟲⟲⟲ etcetera etcetera.
    Temperature runaway, major conflagration

Checking and testing
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Old 05-25-2022, 12:27 PM
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Thanks for your reply Ron. The manufacturer has requested I send the motor back to them for analysis. I've read a little about rewinding these motors and it doesn't seem like something I'd want to tackle.

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