18. PRESENT INSULATION SYSTEMS IN THE WORLD

Four major manufacturing processes have been and are still widely used to form and consolidate insulation systems for form-wound stators. They are:

  1. Vacuum pressure impregnation (VPI) of individual coils and bars

  2. Global VPI of complete stators

  3. Hydraulic molding of individual coils and bars using resin-rich tapes

  4. Press curing of individual coils and bars, also using resin-rich tapes

There are some combinations of these methods also in use. The binder resins can be categorized as high- or low-solvent-containing and solvent less, as well as by their chemical nature. Although no longer manufactured for coils in new stators, there are many machines still in service, and expected to remain in use for several more decades, that are insulated with asphaltic mica splitting.

There are four principal drivers that govern the selection of the insulation systems currently being manufactured. They are:

1. Good service experience with earlier versions of the same basic system

2. Commercial availability of the materials to be used

3. Relative costs of the raw materials and processes in the competitive machine-sales environment

4. Design advantages or limitations each insulation system and process brings to the final generator or motor for its expected service life and economy of operation

New insulating materials may require the development of new or significantly modified manufacturing processes to obtain the insulation system improvements inherent in the materials. By the 1990s, the major insulation suppliers were offering full insulation systems, including the basic processing know-how, to their customers. For smaller OEMs and most repair shops, the insulation supplier’s materials, other acceptable materials, and processing specifications are all that is needed to support work. The final insulation system may use the materials supplier’s trade name, e.g., VonRoll ISOLA’s  Samicatherm™ and  Samicabond™.

Larger OEMs still work with insulation suppliers to optimize both the materials and processes for new or changed insulation systems.