Drying Transformers by External Heat
External heat may be applied to the transformer by one of the following methods:
- By directing heated air into the bottom air inlets of the transformer case.
- By placing the core and coil assembly in a non-flammable box with openings at the top and bottom through which heated air can be circulated.
- By placing the core and coil assembly in a suitably ventilated oven.
It is important that most of the heated air pass through the winding ducts and not around the sides. Good ventilation is essential so condensation will not take place in the transformer or case. A sufficient quantity of air should be used to assure approximately equal inlet and outlet temperatures.
When using either of the first two methods, heat may be obtained by the use of resistance grids or space heaters. These may either be located inside the case box or may be placed outside and the heat blown into the bottom of the case. The core and coil assembly should be carefully protected against direct radiation from the heaters.
