Modern materials and their application in insulating large d-c machines

The tests described are some of the more pertinent used in evaluating new insulating materials for use in large d.c. machines. The test specimens have varied from the simple, varnished blocks, to the complex, a complete d.c. armature, as the test programs have progressed from screening a great many materials to final evaluation of a few. Throughout the emphasis has been placed on employing the systems concept and using functional tests to obtain an understanding of the advantages and limitations of the ever increasing host of new insulation products. Those which have survived comprehensive evaluations of this type are now contributing significantly to the increased reliability of the modern d.c. machines.