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To detect faults in an inverter-fed permanent magnet synchronous motor drive under the circumstance having faults in a stator winding and inverter switch, an online basis fault-detecting scheme during motor operation is presented. The proposed scheme is achieved by monitoring the second-order harmonic component in q-axis current and the fault is detected by comparing these components with those in normal conditions. The non-fault harmonic data in an arbitrary operating condition are determined using the linear interpolation method with several sample harmonic data pre-measured in the stage of the initial drive setup. Once the fault is detected, the operating mode is changed to identify a fault source using the phase current waveform. To verify the effectiveness of the proposed fault detecting scheme, a test motor to allow inter-turn short in the stator winding has been built. The entire control system including harmonic analysis and fault detecting algorithm is implemented using digital signal processor TMS320F28335. Without requiring an additional hardware, the fault can be effectively detected by the proposed scheme during operation so long as the steady-state condition is satisfied.