A strategy for interturn short-circuit fault detection in Permanent Magnet Synchronous Machines (PMSM) is presented. Fault detection is performed by a Residual Voltage (RV) obtained from the difference between the midpoint voltages measured on the semi-windings of each stator phase. To evaluate the performance of the proposed strategy a PMSM model with interturn short-circuit fault and partitioned stator phase windings (semi-windings) is presented. Unlike other strategies that analyze the stator fault on the complete phase windings, the RV obtained from the PMSM dynamic model considering semi-windings allows to detect the incipient stator fault on any of the phase windings. The RV monitoring indicates the occurrence of a fault in stator windings, even for unbalanced supply voltages or asymmetric load conditions. Simulation results to evaluate the performance of the proposed strategy based on the RV signal are presented.