Broken Rotor Bar Fault Detection of Induction Machine Based on Rectified Orthogonal Axes of Stator Current

In induction machines (IMs), the characteristic frequency of broken rotor bars (BRBs) shows modulations by the fundamental frequency, appearing as sidebands in the motor current signature, and often suffering from frequency leakage. This leakage can obscure fault components, potentially leading to catastrophic motor failure. Effective frequency demodulation must separate fault frequency sidebands from the fundamental frequency, eliminate nearby harmonics, and maintain the fault characteristic amplitude while considering the number of measured phases. To address these challenging tasks, we propose a novel method based on the rectified orthogonal axis technique (ROAT), applied to the stator current. The proposed method preserves the amplitudes of the fault characteristic frequency while transferring the energy of the fundamental frequency to the dc value and the fourth harmonic of the supply frequency ( $4f_{s}$ ). This frequency shift is crucial for fault diagnosis in inverter-fed IMs, particularly at low speeds. Our extensive simulations and experiments on motors with several BRBs under single- and three-phase conditions demonstrate the high efficiency and performance of the proposed approach.