EMD-Based Analysis of Industrial Induction Motors With Broken Rotor Bars for Identification of Operating Point at Different Supply Modes

This paper proposes a competent method for broken bars fault identification in line-start and inverter-fed industrial induction motors. The basis of the proposed method is to determine different frequency bands of the faulty motor current and extract a proper intrinsic mode function (IMF) developed by empirical mode decomposition (EMD). It is analytically proved that two specific IMFs, IMF₂ in line-start mode and IMF₃ in inverter-fed mode, can be used for precise prediction of the behavior of a faulty induction motor. The precision of the method is shown at different operating points, including different loads, fault, and reference speeds. The results indicate that the motor asymmetry is remarkably reduced at distributed broken bars. In addition, the proposed method is capable of determining the operating point of the faulty motor even at no/light loads. Finally, the Filippetti criterion is used, and a new aspect is analytically developed to justify the variations of IMF₃ with speed in an inverter-fed induction motor. The analytical results are verified by experiments.