Determination of transformer regulation under load conditions and some resulting investigations

For some time past the writer has been suspicious of the accuracy of the results obtained in calculating transformer regulation by the now popular method of adding the impedance volts vectorially to the pressure impressed on the load, the data for the impedance triangle being obtained by the common short-circuited secondary method and by the measurement of the resistance of the transformer winding. Indeed, the only check on this method heretofore has been the comparison with the direct method of reading the primary and secondary pressures, reduced to like terms, and ascertaining the difference, or, what amounts to the same thing, reading the secondary pressure under full (current) load and under no load, keeping the primary pressure constant the while. These direct methods are inexact unless great precautions are taken due to the impracticability of reading normal pressures with sufficient degree of accuracy for this purpose.