Typical cause of electric mower motor burn out

Factual Questions
1

I was cutting grass with my Black and Decker lawn hog and it quit working and smoke started coming out. What types of motor problems typically cause smoke to come out? I am trying to figure out if I should just junk it or get spare parts.

Thanks,
Rob

2

Often a short, caused by, or leading to overheating. Are you using the proper type of extension cord for this lawnmower?

ETA: That would apply to most devices using an electric motor, not lawnmowers in particular.

3

Smoke can be caused by seized bearings, which by themselves can make smoke, but it’s more likely that the locked motor ends up burning up the coils to make the smoke.

Smoke can also be caused by the coils themselves failing first. The insulation on the wires can break down due to age, or, as TriPolar said they can fail due to overheating. Either the insulation melts or breaks down or the wire itself melts.

Things like cutting grass that is too high, or cutting it too fast, or cutting grass when it is damp will put more strain on the motor which leads to failure faster. Using too thin of an extension cord (also mentioned by TriPolar) will cause the voltage at the motor to drop, which can cause the motor to draw more current (and put more strain on the motor coils) as it tries to keep up with the load demand on it. If you are straining the motor already, doing so in very hot weather with the sun beating down on the motor will make it overheat worse, making a failure more likely.

If it were me, I wouldn’t try to fix the motor. If the rest of the mower is in relatively good condition I’d probably just swap out the motor.

4

A new motor costs nearly $200. It burned out because I was cutting grass that was too high (and it might have been damp too) from what it sounds like. I think I will just pick up another second hand.

Thanks,
Rob

5

those things typically use series-universal motors, which have brushes and a commutator. if overloaded the brushes and commutator can arc enough to start burning away. but if there was a good amount of smoke, I’d think that burning insulation would be the culprit due to overload as TriPolar and engineer_comp_geek already said.