Motor and maybe ESC just smoked on workbench

[Jim85IROC]

The other day I connected my 13.5t motor, x-car 120a esc and Castle BEC. I did a function check and it all worked well. I reprogrammed the esc to add drag brake and be in forward/reverse mode. I left the neutral band at narrow.

The only other change that I made was to plug in the sensor cable. I married the body to the chassis, and when I powered it on tonight, the servo turned to full lock then back to center, then smoke poured out of the motor. It got hot enough for one of the motor wires to come unsoldered.

The whole thing took maybe 30 seconds before I saw the smoke and unplugged the battery.

Any ideas what happened? All I can think of is that the neutral band was too narrow and the drag brake dumped a bunch of current into the motor. Would that smoke a motor in 30 seconds tho?

 

[Hardcoretam]

Sounds like one of the motor wires was plugged in, in the wrong order.

 

[Jim85IROC]

That can burn up a motor that fast, with no throttle input?

 

[JatoTheRipper]

Something was plugged in incorrectly. Yes, they will burn up that fast when wires are reversed.

 

[Hydrocarbon92]

An unplugged sensor wire should put the ESC in sensorless mode & the 3 power wires can be connected any way you want. When you plug the sensor cable in, it changes to sensored mode and requires each power wire at a specific pole/tab.

I can't find a good explanation why this happens w/o throttle input. It probably overheats because it hooks up 1-2 coils at 100% duty due to incorrect sensor readings. A motor with 3 windings would max out at 66%, so it simply turns into a high-current heater. If that's the case, it's silly they can't program in protection such as limiting the time it would power a single winding at zero RPM.

 

[Jim85IROC]

Autopsy was somewhat inconsistent, but I think I'm closer. The 3 poles were connected properly AS LABELED, but I noticed in the controller that the throttle was set to "negative". This is important because this combo came out of a stadium truck that I only test drove for a minute, I believe without the sensor cable. If I reversed the throttle direction on the controller, there had to be a reason.

Additionally, I turned the esc back on after I re-soldered the melted lead and after I disconnected the sensor wire. The motor did not get hot. It appears that the polarity of the motor or esc is not as labeled.

Lastly, when I pull the throttle on the controller, the steering jerks to the side. The motor turns, but poorly.

Next I need to connect a different motor to see what happens, and then maybe a different esc. What a pain.

 

[Jim85IROC]

Replaced motor. Things still seemed glitchy. Replaced ESC. Glitching is gone, but fwd/rev is still strange. With the transmitter set to "normal", the motor goes the wrong way, so I reversed 2 wires, but in doing that, the behavior is clearly wrong. Right now the esc is in fwd/brk/rev mode so I can clearly distinguish forward from reverse. When I go forward, I have to double-tap for it to work. The esc is clearly receiving that input as "reverse", which means that I need to have the controller set to "neg" like it was to begin with. This means that the wiring was also right to begin with, so I still don't have an explanation for why the motor fried. I widened the neutral point. I'm going to hook it back up and see what the hell happens.

 

[Jim85IROC]

I put the controller back to "reverse", plugged the sensor cable in and crossed my fingers. Seemed to work fine, except no reverse. No heat, no glitches. I reprogrammed the esc for fwd/rev, and it's working as expected. The only thing is that it doesn't change direction smoothly. After going forward, it jumps into reverse, and after reverse, it jumps into forward. It's clear that this esc isn't going to be in this truck for too long.