Hawkins Electrical Guide v. 06 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

Ans. Danger of fire.

Ques. What kind of oil is used in transformers?

Ans. Mineral oil.

Ques. What are the requirements of a good grade of transformer oil?

Ans. It should show very little evaporation at 212° Fahr., and should not give off gases at such a rate as to produce an explosive mixture with the air at a temperate below 356°. It should not contain moisture, acid, alkali or sulphur compounds.

Fig. 1,969.—Section through Fort Wayne (type A) transformer showing interior of case, core conductors, and insulation, also division of laminæ.

The presence of moisture can be detected by thrusting a red hot nail in the oil; if the oil "crackle," water is present. Moisture may be removed by raising the temperature slightly above the boiling point, 212° Fahr., but the time consumed (several days) is excessive.