TRANSFORMERS 



447 



perature of 85 C. into coils and insulation at the bottom of the 

 transformer, allowing same to escape at the top. The quantity of 

 air should be such that the temperature of escaping air is approxi- 

 mately the same as the ingoing temperature. Various pipes and 

 deflectors may have to be used to properly distribute the air, 

 and precautions should be taken to prevent oil from running 

 from the transformer into the heater as it may cause a serious 

 fire. The quantity of air to give good results with different size 

 tanks is as follows: 



An outfit which is especially adapted for furnishing hot air for 

 transformer drying is shown in Fig. 282. It consists of an electric 

 air heater blower and air strainer. The air heater requires 20 to 

 25 Kv.A. at 110 or 220 volts to operate it, and the blower about 



FIG. 282. Hot-air Drying Outfit for Transformers. 



2 H.P. to drive it at normal output. The air strainer when in 

 operation should be wrapped with cheesecloth to prevent the dust 

 from entering the blower and being blown into the transformer. 

 This cloth should be changed from time to time as the dirt accu- 

 mulates on it. 



