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Old Sep 06, 2009, 04:00 PM
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Joined Apr 2004
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Blown 2 ESCs, how to tell if motor cause

I've blown a 100a chinese esc (after 10 flights) and a replacement Phoenix 80 (NIB) on first test run on ground after about 5 minutes. Motor was a Aeolianmotor 4250-KV600 with a 11/7E. Full throttle was 550W (45a, 4S 4000 20S) but hardly ever run at full throttle. Ground test was: run motor for a minute (varying throttles), finger test temp of motor, esc & battery, run it for 2 minutes..... Somewhere about 5 minutes of testing, motor studdered, I shut off immediately. ESC was not very hot and showed not the slightest signs of heat damage. Motor was quite hot but not too hot. I disassembled the motor and could see absolutely no sign of winding damage, no colouration, no bearing issues, no sign of rubbing between armature and rotor etc and no burnt smell. My ohm meter could detect no differences in resistance between phases and not shorts to the case (but it is almost useless at the low resistance values of windings).

The next day I mounted the motor on a board to retest with maximum cooling. The motor would not start and the ESC immediately started smoking with the slightest throttle request melting the heat shrink (up to that point it was in perfect visible condition). It will smoke even if no motor is attached. Clearly at least one phase is shorted.

Its hard to believe there is a winding issue in light of no visible signs, smells etc but the only way to know is a destructive cutting the armature in 1/2.

Anyone have any suggestions ? Any experience with NIB P80s failing prematurely at 45amp ? ( a year or 2 old version) ? Any failure mode for motors running too hot that result in excessive current but absolutely no visible damage when dissassembled ? Anyone heard of bearing loading up when heating but going back to normal when cold ? There was some evidence that it was slightly harder to hand rotate the rotor when the motor was hot immediately after the prop "stuttered" (but not grinding). But when the motor was cold , there was no sign of any extra friction and no visual anomalies.

Anyone know of an ESC where all three phases have reliable instanteous over current protection ?
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Old Sep 07, 2009, 06:09 AM
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Blown 2 ESCs, how to tell if motor cause

Try a different motor. Hard to believe 2 in a row would be defective. 99% of failures are user error.

They had trouble with chinese high power ESCs initially but seems the problems were ironed out early on.

Also wouldn't hurt to start with smaller prop and work your way up.
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Old Sep 07, 2009, 08:56 AM
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Ground testing a setup for five minutes is not recommended.

I would check the resistance of all three phases of that motor before I ran it again.

The only phoenix controllers I burned up were user error.
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Old Sep 07, 2009, 12:43 PM
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Antony (France)
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Hi
What about rpm on 4S , or Kv rough estimation ?
Louis
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Old Sep 07, 2009, 01:31 PM
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fyi: In light of unexplained in flight failure of Chinese 100amp ESC (complete with built in bec shutdown) leading to crash, the ground test was an attempt to identify via careful increasing time / (varying) loading the power system for any evidence of replacement P80 ESC overheating or motor misbehaving under load etc. The motor was hotish, the esc was only warmish to my touch. On the upside the test did save a second potential crash (though this setup had a separate bec which might have allowed me to do a dead stick: though with floats, the planes glide path is not great!).

Didn't measure RPM, KV is published at 600

I've reinspected the dissassemblied motor with a magnifying glass and still cannot see any signs of any issues.

I think I have no choice to change the motor (and replace the ESC of course). Thinking of s Scorpion given its claim to have higher temperate rated. That or a Dualsky ? or AXI ?

I wish someone an instrumented protected electronics test bed so the motor could be tested.

Thinking of getting some temperature dots so I can see what temperatures the motor and esc are getting up to. They should build in thermocouples into the motors and escs.

Wish someone made a small squirrel cage fan. Then I could direct air on both the ESC & motor.
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Old Sep 07, 2009, 01:45 PM
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Antony (France)
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Quote:
Originally Posted by DEdwards
fyi:

Didn't measure RPM, KV is published at 600
Hi
Without rpm, V, I recordings and (re)measured Kv it is difficult to analyze
Announced Kv is one thing
But Kv is able to get up

Louis
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