Induction Motors Technical Condition In-Service Testing Methods

Abstract

The article describes methods for in-service diagnostics of the technical condition of induction motors, which are the most widely used type of electromechanical systems. By now, a large number of various studies on this matter have been published. It is stated that the accomplished studies implement an "external" approach to solving the problem, which consists in deriving a diagnostic conclusion based on an analysis of changes in the electric motor external characteristics in one of its operation modes. In addition, these studies are based on two-dimensional models of the classical theory of electrical machines, which does not allow them to adequately reflect situations of multidimensional distribution of electromagnetic quantities in a vector space. These circumstances generated the need to develop more advanced diagnostic methods, called topological ones. Topological diagnostics methods are theoretically substantiated based on the ideas about the IM multidimensional vector space. It is shown that the parametric properties of the vector space and first of all of its working area, have a key influence on the electromechanical energy conversion efficiency. Two methods for testing different areas of the vector space are outlined. In the first case, the space working area is tested for parametric uniformity and operational stability. The results of three experiments provide unbiased and sufficient information about the degree of its homogeneity, about the changes that have occurred during the operation, and about their rates. The testing makes it possible to draw well-grounded conclusions about the electric motor active part technical condition and the degree of its criticality. In the second case, the vector space phase coordinates are tested for parametric uniformity and operational stability. The results presented testify that the proposed testing scheme is sensitive to phase parameter deviations. This is facilitated by the differential principle of its construction. The signal in a short-circuited phase, which appears in the case of a parametric phase imbalance, serves as its clear indicator. The presented mathematical modeling data confirm the efficiency of the proposed testing methods.