New quantitative rotor fault evaluation in wound rotor induction machine drives under time-varying conditions

This paper presents a new diagnosis approach for quantitative rotor faults evaluation in three-phase wound rotor induction machines. In the considered application, the rotor windings are supplied by a static converter for the control of active and reactive power flows exchanged between the machine and the electrical grid. Under speed or fault-varying conditions, the typical rotor fault frequency components, which appear in rotor voltages, are spread in a bandwidth proportional to the speed which complicates its detectability. The proposed diagnosis approach is based on the use of wavelet analysis improved by a pre-processing of the rotor voltage commands. Thus, the time evolution of fault components can be effectively analyzed. Experimental results show the validity of the proposed method under speed and intermittent fault varying conditions, leading to an effective diagnosis procedure for rotor electrical faults in wound rotor induction machines.