WEG Energy, part of leading Brazilian motor and controls manufacturing group WEG — the holding company for the Zest WEG Group, recently installed new vacuum pressure impregnation (VPI) systems at two of its factories in Brazil, effectively expanding its manufacturing capacity for both horizontal and vertical electrical machines with IEC frame sizes up to 2500 and voltages up to 15 000 V. The new VPI systems are designed to allow the impregnation of components with diameters up to 5 metres and heights up to 4 metres, as well as rotors with shafts up to 7 metres in length.
“These investments have boosted WEG’s VPI capacity for larger machines, such as hydro generators, turbo generators, synchronous motors and DC motors,” Zest WEG Group’s ceo, Louis Meiring, says. “The main advantages of VPI include a significant reduction in voids — the empty spaces in the insulation which have the potential to cause partial discharge and damage to the insulation. The system also provides excellent mechanical strength to winding overhangs, extending their lifespan.
“In addition, the VPI process establishes a low thermal resistance path, resulting in a reduced winding temperature. The resin contains no chemical solvents and establishes a shield against external contaminants such as humidity and protects the environment and improves the safety of systems operators. VPI also renders redundant several systems components, such as cooling, heating, vacuum and control, to ensure the stable operation of the entire system, providing a high level of reliability and excellent quality in the final product.”
The VPI process begins with the stator or rotor being placed into the autoclave. An extremely strong vacuum is applied and maintained until all insulation humidity has been completely removed. The autoclave is then slowly flooded with resin, which fully submerses the parts. The vacuum level is maintained until the impregnation process is completed and then autoclave pressure is equalised with atmospheric pressure. A higher pressure is applied and maintained until the online measurement system indicates that the insulation capacitance criteria are accepted. The resin is then drained out and the part is removed from the autoclave and taken to the cure oven.