Insulation of rotating electrical machinery

The paper discusses the use, in rotating machines, of new or improved insulation materials which have become available during the last 25 years, with the object of indicating the advantages obtained by using such materials and also the disadvantages and difficulties attendant with some of them. Practical experience over many years with some of the materials has revealed some serious drawbacks; on the other hand, some materials have proved to be even more useful than was thought at first.