Right: ESC that burnt out completely
Left: ESC that was fire damaged by the other one
We had an ESC burst into flames today. Here's the story.
Pixhawk 4 running 1.8.1
4 T-motor antigravity 4006 380kv motors
4 JHE 40A BL_HELI_32 ESCs
6 cell LiPo
We were running the generic quadcopter airframe with no changes. The ESCs signal wires were just wired to M1-4 on the I/O PWM outputs, with the signal grounds connected to the ESC power grounds (just a standard PWM setup). I'd calibrated all the ESCs with PWM_DISARMED = 900us. We were able to get the motors running, but they were all turning counter-clockwise. So we switched round the PWM signal in QGroundControl for motors 3 and 4 (front left and back right). After a few more times of testing, the motors were still all spinning anti-clockwise, and they also all started spinning really fast when we armed the vehicle, and so we re-calibrated the ESCs at 900us, and re-ensured that the signals on MAIN 3 and 4 were reversed.
Now what I then did (this was possibly not smart), was set PWM_MIN to 950us, and rebooted. The reason was we wanted to test the setup running very slowly, without arming.
When the vehicle rebooted, motors 1 and 2 started turning slowly as expected (we haven't armed at this point). However, motors 3 and 4 weren't turning at all. We were discussing why this might be, but then the ESC of motor 4 suddenly burst into flames! We disconnected the battery immediately and the ESC burned out.
What was really strange about all this, was that the motor connected to the ESC that went out was never spinning at any point. The obvious possible explanation for this would be an internal fault in the ESC that caused a short that bypassed the motor, but I was wondering if anyone could help with the following:
Is there anything that sounds wrong in the setup I've described above, that could have been a potential cause?
For the future, would anyone know why the PWM reverse parameters wouldn't work properly? It's only just occurred to me, but I can't actually remember if we re-calibrated the ESCs after reversing the directions in the software, but I'm guessing that's also a good idea/necessary?
Many thanks for any help in advance.