The VPI process (Vacuum Pressure Impregnation) briefly consists in two steps. At first, the motor is placed in the autoclave and subjected to a dry vacuum process for some hours, time during which all air and humidity are removed. Subsequently, the motor is kept in vacuum for some more time with an EPOXY resin. In the second phase, the motor is placed under pressure with the resin for a few more hours.
The ability of the motor to dissipate generated heat contributes to increase its energy efficiency. Once the VPI system removes all the air from the interior of the winding, the system helps to ensure that there is no loss of efficiency in the motor. As air is also a poor dielectric insulator, its removal and replacement by resin prevents the creation of partial discharges that lead to destruction of insulation.
On the other hand, EPOXY resin is much more resistant to contamination by humidity or other agents, have a slower aging process and is much more durable when subjected to thermal variations and vibrations, whereby certainly contributes to increase the durability of the winding.
The result is an uniform compact insulation system, much more resistant to environment contamination, vibrations, heat and other elements that contribute to reduce the life expectancy of the winding. Additionally, contributes to better energy efficiency.