1 The electric brush and the collector ring contact for point contact or line contact.
2 The electric brush and the collector ring when the installation dislocation.
3 Brush pressure is too large or too small. Excessive pressure, resulting in mechanical wear and tear increase, the pressure is too small, the electrical loss is too large.
4 The surface of the collector ring has oil or sundries.
5 The electric motor is used in the vibration of the larger operating conditions, the brush due to vibration caused by the contact with the collector ring, and therefore the ignition, so that the loss of increased, so that the temperature of the collector ring will also rise.
6 brush grade is not correct, the current density is too large.