Induction motors are very commonly used in industry. From that reason more and more often different methods of induction motor diagnosis are applied. In this article motor current signature analysis (MCSA) method is presented with special Extended Park’s Vectors Approach. This method extends the possibility of current signals analysis in frequency domain giving better recognition of some faults. In the presented experiment few malfunctions were applied to the laboratory stand which consists of two different induction motors. In both cases they were supplied from frequency inverter, therefore additionally influence of this type of control on current spectrum is presented. The results of presented research and gathered experience in this domain are the basis for the elaboration of advanced on-line diagnostic system for industrial object.