Diagnosis of induction machines under non-stationary conditions: Concepts and tools

This paper is focused on fault diagnostic methodologies suited for induction machines which are subjected to fluctuating loads and speeds during their normal duty cycle. In these cases, the load and speed fluctuate continuously, near their rated values, and in a random way; the diagnosis becomes more complicated than under stationary regime or under other kind of transients, as the startup, much intensively studied at the literature, in which the speed, slip, and current undergo larger variations and evolve in a predefined way. In the first part of this paper, different approaches which enable the diagnosis under non-stationary conditions are introduced from a conceptual perspective. The second part of this work is devoted to the practical implementation of the diagnostic approaches previously introduced: the suitable signal analysis tools needed for carrying out diverse diagnostic approaches are introduced in a comprehensive way and supported by experimental results.