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This article presents a comparative investigation of various media for non-invasive diagnosis of mechanical abnormalities in induction motors. Stator voltages and stator currents as well as noises on these signals are simulated first for a fault-free motor then for a motor with mechanical abnormalities. These signals are subsequently employed to compute the instantaneous powers P ab , P cb , P abc and last the current Park vector modulus known as the extended Park vector approach (EPVA) method. Waveforms of these simulated signals were analyzed using the power spectral density transformation. Commercially available diagnostics systems use the fact that the amplitude of some components known as fault characteristic frequencies in these electrical signals increase when mechanical abnormalities occur. The amplitude increase of these characteristic frequencies is employed as a criterion in order to investigate noise immunity of the five diagnosis methods, thus making possible their classification. Si...