A Method of Assessing the Service Life and Reliability of Motor Brushes Based on Wear Under Variable Current and Environmental Conditions

Wear behaviour determines the service life and reliability of the motor's commutator and Brush, including mechanical and electrical wear. The temperature and relative humidity, especially humid tropical climate conditions, significantly affect the wear behaviour of commutator brushes. The traditional life tests are often manual and time-consuming due to a long expected life. This paper presents study results on the service life and reliability of graphite brushes when the temperature, relative humidity, and current change. The calculation method of service life and reliability depending on wear testing was used to evaluate the service life characteristics. The experimental results, service life, and reliability calculations showed that the service life and reliability of the graphite brushes were influenced clearly by current, temperature, relative humidity, and the probability of failure-free operation. It depends on the current more than relative humidity and temperature. In the range of changing current in this study, the service life: TP(99%) ~ 0.54*TP(50%), TP(95%) ~ 0.62*TP(50%), and TP(90%) ~ 0.68*TP(50%).