Essential motor health monitoring

This paper explores what motor monitoring tools are available today to give the user proper tools to make informed decisions about when a motor needs maintenance, or even replacement before an unexpected failure occurs. It will first present a new approach to detect motor abnormal temperature rise which is possible due to degradation of the cooling system. This new functionality will compare expected motor temperature at a certain load current with an actual temperature obtained from RTDs, and is applicable to all motors thus equipped. Specific data is presented for the applicability of this monitoring technique to breathing versus enclosed motors. Significant deviation between expected and actual motor temperature rise values are an indication that the motor cooling system is not working properly and maintenance is required. This essentially means condition-based assessments of motor cooling versus routine, time-based motor cleaning. Secondly this paper will present other useful information, which can be obtained from modern digital relays, including learned data and trending of the motor starting currents and time, frequency and causes of the motor stops, increase/decrease of the load and unbalance over time, emergency restarts, motor operating temperature trending and many others.