Induction Machines with Rotor Faults: Analysis of the Physical Quantities for Different Operating Conditions and Machine Sizes for Improved Diagnostics

This paper extends the authors' deep investigation of the electric rotor fault signatures of induction machines to machines of different size operating in various conditions. Authors researches have already shown the limits of the usual diagnostic procedures based on the sum of both left and right current sidebands. A proper faulty machine model leading to a more robust diagnosis has been proposed and the effect of machine size and load conditions on current space vector sidebands, flux, torque and speed spectral components is shown. These physical quantities, in case of small faults, can be described by their representative phasors in a synchronous reference frame. The analytical links among the phasors are validated by simulations and experiments. The prominent role of mechanical inertia in the diagnostic process is highlighted, assessing the range of validity of the usual diagnostic index versus machine size and load, eventually an alternative procedure is here proposed.