Rotor fault detection in closed loop induction motors drives by electric signal analysis

This paper deals with the diagnostic procedures that can be applied to assess the severity degree of rotor faults in closed loop induction motor drives with different control architectures. field oriented control (FOC), with or without speed loop, and direct torque control (DTC) are investigated in order to validate the robustness of the diagnostic procedures versus control regulator parameters and motor load. This paper investigates a variety of diagnostic procedures based on several electric quantities depending on control architecture, as a matter of fact spectral components of motor currents and motor voltages, of manipulated and controlled variables, and the third harmonic of voltage zero sequence are taken in to account as possible fault alert signals or diagnostic indexes. Eventually the spectral components of motor currents due to a high frequency voltage injection are considered as well. It turns out that these components, if injection frequency is suitably chosen, give a simple and effective index, independent of the control structure and of control parameters, able to detect and quantify the fault severity.