The book contains the most important information about the classification and design of insulation, the technology of insulation, drying and impregnation of windings, control and testing of insulation in the manufacture and repair of electrical machines of various types and versions. The material given in the book is based on the experience of Soviet electric machine-building plants, as well as on the experience of operating electric machines. The book is intended for engineering and technical workers related to the design, production, repair and operation of electrical machines, and can also be useful for students of technical colleges and technical schools who want to deepen their knowledge in the field of isolation of electrical machines.