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This paper presents an inverter open switch fault detection method which is based on voltage measurement and then uses inverter output voltage estimation for the more reliable detection. To detect the open switch fault, general voltage measurement based methods compare a reference voltage with measured voltage. However, although the system is under healthy condition, there exists voltage deviation between the reference and measured voltage due to non-ideal switching behaviors of the inverter. In addition, because the difference between two AC quantities varies in one rotation cycle, it is difficult to determine threshold value. To overcome these problems in practical case, the presented method uses an estimated voltage instead of direct use of the reference voltage. And a sectoral average value of the difference is defined as a residual instead of instantaneous one. Several sets of experimental results validate the detection capability of the proposed method.