ANALYSIS AND COMPARISON OF MAGNETIC SHEET INSULATION TESTS

Magnetic circuits of electrical machines are divided into coated sheet s in order to limit eddy currents. The surface insulation resistance o f magnetic sheets is difficult to evaluate because it depends on param eters like pressure and covers a wide range of values. Two methods of measuring insulation resistance are analyzed: the standardized 'Frankl in device' and a tester developed by British Steel Electrical. Their m ain drawback is poor local repeatability. The Franklin method allows b etter quality control of industrial process because it measures only o ne insulating layer at a time. It also gives more accurate images of t he distribution of possible defects. Nevertheless, both methods lead t o similar classifications of insulation efficiency.