Calculation of faults between core laminations and prediction of axial damage depth of large motors

Abstract

A method to analytically calculate the parameters of the fault area between core laminations are proposed and the dynamic trend of the fault development is predicted to comprehensively and accurately obtain the fault degree and damage level of short-circuits between the core laminations of large motors. Considering the influences of frequency and magnetic flux on the axial skin depth of the core and of the eddy current loss on the insulation resistance between the laminations and reviewing the laminations of the stator core tooth as the research object, based on the Maxwell equations and equivalent circuit theory, analytic expressions of active power and induced voltage in the fault area between the laminations are derived; the influence of the number of fault laminations on the electrical parameters in the fault area is quantitatively analyzed; the actual fault development process of the short-circuit faults between the laminations are obtained; and the correctness and effectiveness of the proposed method are verified via numerical simulations and the experiment of faults between core laminations. The sequence of induced voltage changing with the number of fault laminations is selected as the grey sequence to establish the grey prediction model (GM (1,1)). The development curve of the damage depth of the faults between core laminations along the axial direction is illustrated by calculating the sequence data. The results show that the error between the predicted value of the damage depth of the short-circuit fault herein and the experimental value is less than 7%. This method can be used in engineering practices.