How to judge and solve?
The possible reasons are:
1. Armature winding connection failure
2. Mica highlights
3. Commutator riser connection disconnection
4. The commutator is loose
5. Brush material does not match motor and load
Solution:
1. Find a manufacturer
2. Mica grooving or using wear-resistant carbon brushes
3. Welding at the joint
4. Tightening the commutator or rounding, rounding, mica replacement
5. Use the recommended carbon brush material and carbon brush structure