Windings, vacuum-pressure-impregnated

For large motors, the practice is to wind the stator with formed coils (Figure 9.2). The coils are pre-formed and cured before insertion into the stator slots. They are insulated with resin-rich glass and mica paper tapes. The process of impregnation is therefore termed resin-rich insulation. The completed formed wound stator is then heated to remove trapped moisture and finally impregnated in varnish class F or H as required, under vacuum and pressure. The stator is then cured in an oven as described above. The process of insulation and curing conforms to powerhouse insulation requirements. This practice facili-... 

Impregnation Results in complete coverage of intricate and closely spaced parts. Seals fine leaks or pores. Requires vacuum or pressure cycling or both. Spe- Coils, transformers, field and armature windings, cial equipment usually required. metal castings, and sealing of porous structures. ... 

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