One of my four ESCs burnt out on a first test flight of a new quad build. I plugged the battery in, armed the drone, and one of the motors spun for less than a second before stopping. I immediately saw white smoke and smelled burning plastic. This all happened with the throttle set to idle. The other three motors are working fine even under load.

I opened the ESC to take a look, and sure enough, one of the FETs shows signs of burn damage. This same motor was operating correctly and responsive on the test bench, without a prop. I also noticed that this ESC gets very hot to the touch - 80C maybe - even when disarmed (but powered).

What could be the cause? Is a bad ESC likely? I'm wondering if it's a short, but the fact that it was responsive on the bench makes it seem unlikely.

30A Simonk ESC

920KV Motors

4s LiPo

Matek PDB

8" props

  • After swapping the ESC with a spare, the motor spins up. I am guessing that the burnt ESC was either defective, or perhaps some contaminant got into the shrink wrap during assembly and caused a short. – SkyNT Jul 7 at 17:17

On the bench without propeller your motor as virtually no load, hence the current rained from the ESCs is rather low.

Then seeing the average price of your ESCs on the internet I would not be surprised if once in a while one is faulty ... As it worked fine on bench and all the other work, I would rule out software and mismatching ratings respectively.

Your ESCs are maybe a bit oversized (currentwise) w.r.t. your motors rating but this should have no impact (expect for price and weight).

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