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Fried motors

Posted by Tj Bordelon on September 27, 2010 at 8:00am
Doomed flight is here:



Hobbypartz.com has great prices and great motors. I think. But for some reason I seem to be having some very bad luck frying motors lately.

I've been running one of their 450TH motors rated for 230 watts (http://www.hobbypartz.com/45oubrmo6.html) at exactly 230 watts, and haven't had much issue with very short bursts at the 230 figure of 40 seconds or less for takeoffs.

BUT-- For the first time I flew full throttle the entire flight, mostly due to winds, and the motor and controller both fried. That's 20 amps through at 25 amp controller, 3 cell lipo, which is roughly 230 watts. This outrunner motor is out in the open air, so it shouldn't be overheating.

I know the rule is probably to run way under the motor's rating, but what do you guys think? Is it unreasonable to expect a 230 watt motor should run 230 watts for at least a few minutes? This is the 3rd motor that has done this to me, and I am starting to think that I should be running 80% of maximum as a rule and see if that gets me any better luck.

One possibility though. I have to limit max throttle to 75% to keep the current at the maximum of 20 amps. Could running a controller in this way cause problems?

Thanks for any ideas!
Tags: autopilot, easystar, fried, motor
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Comments

  • Tj Bordelon October 7, 2010 at 2:23pm
    And this awesome description of how ESC's work basically says that heat comes from the switching... and the FETS see 100% throttle even at partial throttle. So that's why I blew it.

    http://www.rcgroups.com/forums/showpost.php?p=10026876&postcoun...
    RC Groups - View Single Post - Scorpion Motors: Questions and Answers....
    RC Groups - the most active Radio Control model community: electric and fuel rc airplanes,rc helis,rc boats and rc cars. Features discussion forums,…
  • Tj Bordelon October 7, 2010 at 2:10pm
    And the answer is...

    "Because each on pulse is 100% of full throttle current, a system set to pull 20 amps at full throttle through a Phoenix 10 will not last if you are throttled back to the point where you only see 10 amps on a wattmeter. The ESC in this case is still switching 20 amps, which it can’t do for long. Actually it is worse than the simple example above. Because an electric motor will always to try to pull as much power as is available to get to its rpm (volts times Kv), when you are running the motor below its Kv speed by switching power on an off, each on pulse will actually be way over the full throttle amp draw."

    ... I forgot to mention that I limited my full throttle to 70% because at 100% I was way over my speed controller's 25 amp limit. Apparently you can't do this.
  • Ed Stewart October 2, 2010 at 9:03am
    Speaking of Motor Timing, are there some general rules for setting low, mid, or high timing modes for various motors. When I get time I intend to do some bench testing with my infra red temperature sensor on some motors I have laying around on my work bench.
  • Riccardo Kuebler September 27, 2010 at 12:58pm
    The last motor I was using on the Funjet is a Neumotor. I calculated that I was using it well over the specs. The seller said me that if I was able to fry it, he was going to replace it for free. I'm speaking of Remo Frattini (the F5B World Champion), so I guess I can trust him.
    Btw still not fried :D

    Ric
  • Tj Bordelon September 27, 2010 at 12:38pm
    @JamesF - Thanks! Those are great looking motors. After I fry my new Turnagy motor, I'll give those a go.
  • Öncü Kayalar September 27, 2010 at 12:18pm
    Riccardo,
    small to mid size out-runner motors for quad use :)
  • Riccardo Kuebler September 27, 2010 at 12:16pm
    Öncü,
    it depends for what use :)
    Ric
  • Riccardo Kuebler September 27, 2010 at 12:13pm
    Tj,
    I fried an ESC in flight because a short in the motor (melted connecting cables !) on my Funjet and another ESC on another plane (don't rememe why), but fortunately I never lost BEC (then RC and AP controls).
    I guess that if the problem comes from motor side it would (should) not affect the BEC, if it comes from battery side (short), well, I guess your problems are a little worst :D
    Obviously a burned ESC is another story ...

    Ric
  • Öncü Kayalar September 27, 2010 at 12:10pm
    Which brands do you guys recommend?
  • James F. September 27, 2010 at 12:08pm
    I wouldn't bother with cheap motors unless you plan on running them way below rating. For the money you end up spending on 2-3 cheap motors, you can easily buy a high quality ARC motor or Neu motor. I have personally flown my 500w ARC well past double the rating (1200+) in bursts and double sustained. With a bit of airflow the motor barely gets hot.
    http://www.lightflightrc.com/
This reply was deleted.