The purpose of vacuum drying is to remove moisture in the transformer.
Transformers with voltages greater than 3 kv must vacuum dry and must also undergo a drying process to remove moisture within limits to ensure the transformer has sufficient dielectric strength and service life. With long-term operation, transportation, or assembly, the solid insulation of transformers is humidified by the environment. As a result, a decrease in the level of resistance in the windings, an increase in leakage currents and loss tangent.

Can be used for component drying, resin degassing, vacuum resin preparation