Methods of determining temperature of transformers

Temperature in electrical apparatus is an important factor. It affects the life of the apparatus. II. Temperature of transformers is affected by room temperature, circulation of air, design of case and arrangement of coils. Each part of apparatus should be ventilated according to its individual requirements. III. Discussion of tests to determine efficiency of cooling. Rules are given for determining approximately the maximum temperature of the windings. IV. Standard methods of loading transformers are described. The direct loading method is rarely used, on account of the expense involved. The artificial methods at present in use are applicable only when two or more similar transformers are available. V. The alternate open-circuit and short-circuit method is described. It is useful when there is only one transformer on order. Theoretical proof of the method is given. VI. Tests are made by the new method on both self-cooled and water-cooled transformers. These tests are found to agree closely with results obtained with standard tests.