Evaluation of a diagnostic information on common electrical faults contained in signals of an inverter-fed AC IM drive with current-oriented control

Diagnosis and fault detection become nowadays very important feature of modern drive control system capabilities. The subject of interest in this paper is a fault diagnosis in a voltage inverter-fed AC drive with squirrel-cage induction motor with vector current-oriented control (COC). For this purpose the Short Time Fourier Transform (STFT) based on analysis of stator currents and voltages waveforms representing by appropriate controller internal signals was used. Some waveforms acquired on real test-stand with 2kW induction motor which were the basis of this analysis are enclosed. Proposed method of the signal analysis allows to detect intermittent work of inverter power switch fault, stator winding asymmetry fault and inter-turn short circuit fault. It was shown also that the appearance of the second harmonic in analyzed signals and changes in the first harmonics amplitude allow to detect faulty states of inverter switches.