Motor troubleshooting

[Eric Lamberts]

I have a motor that doesn't work after a crash. The prop was held from turning for maybe 20 seconds. I finally got it turned off.

Motor looks normal, turns freely, not out of round, a few scratches on the shell. Was not hot and no electrical odor.

Now when I try to start the motors, the 3 uninvolved one rev up and won for a fes seconds, the involved one does nothing and then it turns itself off.

Research says either a bad motor or a bad ESC. There is no error message. If it were the EXC wouldn't there be one?

Quite the drama with this thing, got it used and had to update the firmware . Finally got it working but could not arm the motors, As it turns out It does better if I use it farther from the airport. Pretty frustrating figuring that out. Also frustrating since the Crow Flies distance calculator says I'm Six miles from the airport.

Thanks! Eric the newbie.

 

[alokbhargava]

It may be worth checking if any connection to motor is cut. In that case motor won’t turn and esc will shut the system after powering on after seeing the current unbalance beyond the limit.

Buy right type of motor and replace it. Motors are not very expensive but got to be reliable for safe operations.

 

[solentlife]

When an electrical motor such as these is stalled by prop held ... the amps climbs seriously high trying to turn the motor ... at which any of the following can occur when it gets high enough :

a) Motor winding burns out
b) Motor lead fries and breaks away
c) Winding or motor lead fries and insulation breaks down shorting out
d) ESC burns out on overload
e) Any power lead to / from ESC fries


The problem to diagnose a motor failure is not easy for the drone only user ... as he generally will not have access to ESC and power source separate as from another RC model. It would be a case of connecting the 3 motor leads to the regular brushless ESC, ESC power to a LiPo and a Servo tester to control throttle ... see if motor runs ok. There is no way to just apply power to a Brushless Motor like these - its not like brushed two wire motors.
But for average drone user - you don't have such gear. So its process of elimination.
Also DJI integrate ESC and boards - so only remedy if ESC has blown a FET etc. - is replacement board !

You could buy a replacement motor - cheap enough ... but my gut feeling tells me it might be the ESC ... as you say there is no smell ... or Magic Smoke as we usually call it in RC world !!

One way to check if motor or ESC .... is to swap over two motors - one being the questionable ... if it runs in the other position and the good one fails - then its ESC. If the good one runs in the questionable slot and other fails in good slot - then its motor.

Do this with props OFF please !! You also will need to have top shell connected but loose and held etc. If any items is not connected - FW will refuse to allow start up.

Nigel

 

[Eric Lamberts]

Thank you very much for your answers, I ordered a motor, but like the Idea of switching the motors sounds like a good one to figure out where the fault is. The aircraft is s Phantom 3 pro, btw. I might have access to the test unit you described but just switching the motors is simple and elegant. I fear it is the esc, as you suspected, burning wires and motor have smoke and heat. No evidence of either,, I'll kee you posted.

Thanks again.

 

[Eric Lamberts]

So. if the ESC IS bad, there would not necessarily be a ESC error code?. anyone ever repair a board? I'd expect it to be one component or a burned printed circuit.

 

[solentlife]

One of the problems and sadly - many seem to forget this when suggesting solutions ...

The DJI systems all work together and a fault in one can be hidden by a fault elsewhere. You can have an event or warning - but when you fix what you think it is - another warning comes up for another ...

The items are too interlinked in operation. The number of posts where people replace ribbon cable ... or gimbal arm ... and still it doesn't work - just throws up another error warning.

Unlike conventional RC gear where items are separate - DJI has integrated so much.... even farmed out parts of the operation system to other boards confusing the issue.

I would swap motors first ... see what that does. As to replacing ESC's ... I cannot answer if possible as the ESC's are part of the main board in the centre shell ....

Nigel

 

[Eric Lamberts]

Good News! I went out of airport range where I can arm the motors and all four worked. I suspect that DJI has some sort of overload protector that protects against serious damage that resets with an adequate cool down period. My problem with troubleshooting is that I live within 5 miles of an airport no fly zone and I cannot even arm the motors without driving somewhere.

 

[Mark The Droner]

Try placing several layers of foil over the top of the AC to block the satellite receiver...

 

[solentlife]

great news ...

 

[Eric Lamberts]

I might try the aluminium foil trick Today the motors armed jus fine in the driveway.