Significance of joints due to lamination segmentation on shaft current in induction machine

An industry-university research partnership program between GE Peterborough and McMaster University (Canada) was instituted to study shaft current phenomenon in an 8-pole 2611 kW induction machine. The study reviewed all the possible causes of bearing damage. A series of experimental tests were carried out to determine the cause(s) of the shaft current. These tests include oil analysis, bearing damage analysis and no-load running tests. The test results are presented. The tests were conducted using a novel method of shaft current measurement. In addition to the test results, this paper presents a simplified pictorial representation of the significance of joints due to lamination segmentation on the occurrence of shaft current. The paper also includes shaft voltage prediction rules.