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Hot Hot Motor!

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Old 09-11-2018, 11:58 AM
  #1  
FlyingGreg
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OK, this is entirely my fault. The rear of the motor was rubbing against the firewall. I had remounted after a crash and apparently did not get the motor centered. At any rate, the extra friction cause the motor to overheat to the point the epoxy holding the magnets soften enough to let a few of the magnets loose, essentially trashing the motor. It was so hot you could not touch the cowl. It was a Turnigy .60 sized motor and a YEP 80 amp ESC. I know the motor is gone and have ordered a new one, but my question is about the ESC.

Since everything got so hot, I am assuming the ESC is toast also and have one on order. However, I am tempted to try and use the one that got the extra heat. I will add that it got hot enough that one of the motor leads "un-soldered" itself. Just for grins I am going to re-solder and give it a try on the bench.

Thoughts or comments?
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Old 10-03-2018, 03:27 AM
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The issue is going to be did the current drawn by the motor over load the ESC. If the motor was actually still running at the end then the ESC should be ok. If the motor stopped "un-commanded" then it is a toss up as to whether it was the motor or ESC than failed first.
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Old 10-04-2018, 04:00 AM
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Thanks Quorneng--I did re-solder the center lead back onto the ESC and it seems to be working. Have not flown the plane yet but will prepare for mid flight failure. Confident that I can land the plane (4*60) without incident if motor dies.
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Old 10-26-2018, 04:21 PM
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  • Overheating magnets causes de-magnetizing (irreversible! ), which in turn results in higher Kv. Motorcurrent is proportional to Kv³ , and resistance losses in the copperwire are proportional to current². Therefore resistance losses are proportional to Kv⁶!!!
  • Hotter motor → weaker magnets → higher Kv → higher current → hotter motor → weaker magnets → higher Kv → higher current ⟲⟲⟲ etcetera etcetera, temperature runaway, major conflagration
  • Several motor tests
    1. Determining whether magnets still have original strength, by determining whether Kv motor parameter (in rpm/volt) is still the same, several simple straightforward methods.
      www.bavaria-direct.co.za → motor constants
    2. Generator test, only using a power drill and a voltmeter
      (Re)winding and building motors - RCG (sticky) → opening post → #40 Generator test
    3. Drytesting brushless motors - WFF (RCG user vollrathd)
    4. Opening an outrunner for visual inspection

    Prettig weekend Ron
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Old 10-27-2018, 01:02 PM
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Originally Posted by FlyingGreg View Post
Thanks Quorneng--I did re-solder the center lead back onto the ESC and it seems to be working. Have not flown the plane yet but will prepare for mid flight failure. Confident that I can land the plane (4*60) without incident if motor dies.
Providing if it does fail it will be the motor control only that fails and not the whole esc including the on board bec. If there is a complete failure of the esc you may not have any power to the receiver and servos. Might waist a plane if that happens.

Dennis
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Old 10-29-2018, 05:17 AM
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Thanks Ron and Dennis. I put a new motor on the plane and although I have a new ESC, the one I fixed seems to be working quite well.
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