Research on the modeling and fault diagnosis of rotor eccentricities has been conducted during the past two decades. A variety of diagnostic theories and methods have been proposed based on different mechanisms, and there are reviews following either one type of electric machines or one type of eccentricity. Nonetheless, the research routes of modeling and diagnosis are common, regardless of machine or eccentricity types. This article tends to review all the possible modeling and diagnostic approaches for all common types of electric machines with eccentricities and provide suggestions on future research roadmap. The paper indicates that a reliable low-cost non-intrusive real-time online visualized diagnostic method is the trend. Observer-based diagnostic strategies are thought promising for the continued research.

On the basis of predecessors, a theory named inverse transient complex inductance vector is proposed for air‐gap eccentricity fault diagnosis of interior permanent magnet synchronous motors, and a specific voltage sequence injection method with simple implementation is proposed here. It is a real‐time visualised diagnostic approach. A unique fault index is proposed to diagnose eccentricities. The absolute value of the fault index is positively correlated with the total eccentricity degree. Three types of artificial eccentricities and one type of artificial partial demagnetisation are tested. Both simulations and experiments match the proposed theory and diagnostic approach. The approach gives a clear distinction in detecting air‐gap eccentricity and partial magnet demagnetisation. It performs best in the low‐speed operating condition.