Discussion

1. There are many variables entering the compromise heat run taken with singlephase current and 3-phase excitation. To establish an acceptable heat run practice for this type of compromise will of necessity require a complete analysis of the physical structure to be tested as well as temperature gradients, casing material, and spacing, and perhaps still other variables including electrical losses and impedance. It is suggested that consideration be given to winding ratio adjustments made by tap setting to reduce "proximity" factors to a minimum. 2. A straightforward excitation run followed by a current run seems to offer the simplest approach. Although it is somewhat more time-consuming, it can be performed with the same facilities usually found in areas used for testing transformers. 3. If further testing shows that simple equations such as equations 15 and 16 of the paper are applicable to the many types of ventilated transformers now being manufactured, a major contribution to the art will have been made.