Abstract Like any other machines, motors and generators are subject to wear and aging. The materials and components they are made from degrade over time, and if no action is taken this degradation will eventually lead to failure. In critical applications, as in the petroleum industry, a failure can have dramatic and expensive consequences. Fortunately most types of failure can be prevented by maintenance. To plan maintenance effectively, the plant operator must have accurate information about the status of the equipment. In particular, the operator has to know which components need repairing or replacing, and when. Advances in technology and communications mean that it is now possible for decision makers to access real-time information on the condition of their motors and generators.