Temperature-Rise Tests on Ventilated Dry-Type Transrormers

The thermal testing of ventilated dry-type transformers, because of their different thermal structure as contrasted to oil-immersed transformers, requires consideration of, and provision for, evaluation of effects that are different in magnitude and in rate of temperature change. Thus different testing methods, precautions, corrections, and compromises are necessary to obtain reproducible test results. Data are presented utilizing various thermal testing methods for several representative units; suggestions are made for correlating these methods. Indications are also given regarding the relative accuracy of the results.