Insulation Systems for Rotating Low-Voltage Machines

The insulation systems of low-voltage rotating machines tend to be relatively simple, but nevertheless comprise several materials that must be selected to work together. The insulating components can be classified into three groups according to their function, including magnet-wire insulation and the ground/slot and phase insulations, the so-called major insulation. The impregnating liquid (varnish or resin) is also an essential component of most low-voltage insulation systems. Its glues the coils, providing mechanical strength and reducing coil vibration. Polyester, polyesterimide, and epoxy are the principle chemistries for this application. Adhesive tapes, lead sleevings, cords and rigid materials, as for instance the rotor end ring, complete the listing of low-voltage insulating materials, and are used as process aids and considered minor insulation. This paper reviews the types and uses of the insulation components within a low-voltage insulation system.