The impregnation varnishes and resins have as main objective to hold together all the enameled wires they have in the coil with all the components of the stator and fill the voids inside the groove. The union of the wires can prevent them from vibrating and striking each other.
This friction can cause wire enamel to fail, causing a short circuit. The removal of the voids helps in the thermal dissipation of the heat caused by the driver and, especially in applications of motors fed by frequency inverters, can prevent or even decrease the formation of partial discharges, known as corona effect, inside the electric motor.
Two types of varnishes and two types of impregnation resins, all polyester based, are normally used to meet all possible building and application needs of the engines. Silicone resin is only used in the case of specific engines manufactured for very high temperatures.
The varnishes and resins optimize the thermal and electrical characteristics of the materials used, being assigned to them, a higher thermal class to the impregnated materials, compared to the same materials without impregnation.