A: There are two kind brushes we normally use: the metal brush and carbon brush. We choose based on the speed, current and lifetime requirements. For quite small motors, we only have metal brushes while for big ones we only have carbon brushes. Compared with metal brushes, the lifetime of carbon brushes are longer since it will reduce the wear on the commutator. But for low speed motor, the carbon dust might not be able to burn in time which will cause failure too.
Q: Is there a detailed lifetime for your motors?
A: A: I am afraid not. The lifetime varies a lot for different models, materials and the operating conditions like temp., humidity, duty cycle, input power, and how the motor or gear motor is coupled to the load etc. And the lifetime we normally mentioned is the time when the motor rotate without any stop and the current, speed and torque change is within +/-30% of the initial value. If you can specify the detailed requirements and working condition, we'll make our evaluation to see which one will be suitable to meet your needs.