The Low Frequency Heating technology works by applying a current to the windings (about 50% of rated) at a low frequency (in mHz) so that leakage flux in the windings is negligible and the applied voltage is very low (due to low impedance voltage). This causes the temperature to be the same across the winding and thus the windings and insulation can be efficiently heated. The process is carefully controlled to ensure a safe drying process. Before commencing LFH process, hot oil spray is done on Core-winding. Once winding temperature reaches about 40°C, apply Vacuum to effectively remove moisture at rapid rate. Temperature of windings is continuously monitored & measured. Keep collecting water extracted from windings, from vacuum pump on daily basis. Once moisture (water) collection is considerably reduced, dry Nitrogen of high Dew Point (-80°C) is purged to break vacuum and hold for few hours. Refer following table to ascertain the level of dryness achieved. If satisfactory Dew Point is achieved as per table below
