Identification of spectral components in the line current of eccentric salient pole machines using a binomial series-based inverse air-gap function

Current literature does not provide any generalised method for specific permeance - magneto-motive force-based approach to predict all possible harmonic components in the air-gap flux and line current of an eccentric salient-pole machine. This study provides an elegant solution to express specific permeance of an eccentric reluctance synchronous machine as a summation of constant coefficient co-sinusoidal terms. Binomial series expansion has been used to achieve this. The analysis has been validated by matching the presence of the predicted harmonic components in the stator line current by coupled magnetic circuit simulation based on modified winding function approach and experimental results. It is also shown that the effect of sensor errors, machine asymmetry, supply harmonics etc. can be minimised by residual estimation to vastly improve detection sensitivity under all load conditions. Thereafter, a procedure to identify fault type and severity has been presented.