Abstract: The normal operations of motor drive systems are directly related to the safety and reliability of inverters. Based on the analysis of switching function model for inverter under both normal and fault statuses,a novel simplified rapid diagnosis approach for component failures was proposed in this paper. Due to the different voltages endured by an IGBT under normal and fault modes,the simple hardware circuit was adopted to detect and locate open-circuit faults. To ensure effectiveness and reliability of the proposed diagnosis method,the raise edges’ delays of switching signals were used to avoid false diagnosis,and the delay durations were determined considering various factors. The presented diagnosis approach was validated by induction motor variable voltage and variable frequency （VVVF） control system as well as permanent magnet synchronous motor field-orientation vector control system. The experimental results demonstrate the efficiency of the proposed method for diagnosing single component and arm open-circuit faults.