FRA Indicator Limit for Faulty Winding Assessment in Rotating Machine

This paper presents a study on the applicability of frequency response analysis (FRA) for diagnosing faulty stator winding of a three-phase induction motor. Initially, two different faults were simulated on a 2.2 kW induction motor. FRA tests were performed on the units before and after the fault to observe the influence of the fault on the response. Three statistical indicators were used to compute the amount of changes between responses. This was done on three different frequency ranges, which are low, medium, and high regions, as each region was governed by different winding parameters, namely winding resistance, inductance, and capacitance, respectively. Consequently, benchmark limits for two indicators, ASLE and CC were proposed for the estimation of normal and faulty winding conditions. Finally, the result also presents FRA measurement on 6.6 kV, 1700 kW induction motor, which clearly indicates the perfect correlation between responses, hence normal winding.