Global vacuum and pressure impregnation of high voltage stator windings

Global vacuum and pressure impregnation (v.p.i.) techniques for stator windings have been used on small output machines, i.e. below 2 or 3 MW for many years. It is now accepted practice to manufacture v.p.i. windings for machines up to 20-25 MW with line voltages to 13.8 kV. Units of this size, for general industrial drives, have been in service for at least 15 years and orders for larger machines and higher voltages are now being placed. The author describes the advantages of these large, high voltage, global vacuum and pressure impregnated windings. The author also describes two aspects of the system which differ from resin-rich windings and prompt most attention in end-users specifications, i.e., coil to core contact within the slot portion and the integrity of the end-winding bracing system