Pole proximity effect on EL CID results

A three-dimensional finite element analysis of the magnetic field between the stator and rotor of salient-pole hydroelectric generators has shown quantitatively that end leakage flux produces distortion of EL CID (Electromagnetic Core Imperfection Detector) results, which are obtained relatively close to the side of a pole piece. The conclusion is in agreement with results obtained from two test cases. This was expected for the first machine, but a careful reappraisal of the test results for the second machine was required to establish a correlation with the 3D-FE analysis, as a pole proximity effect had not been obvious initially. The further conclusion is that EL CID results obtained with the rotor in-situ would inevitably be subject to distortion due to the pole proximity effect. Recognition of this permits it to be taken into account.