Abridgment of graphical determination of magnetic fields theoretical considerations

Three papers on the general subject, “Graphical Determination of Magnetic Fields,” are being presented simultaneously to cover three phases of the subject: 1. Theoretical Considerations, 2. Comparison of Calculations and Tests, by E. E. Johnson and C. H. Green, 3. Practical Applications to Salient-Pole Synchronous Machine Design, by R. W. Wieseman. In the complete paper, which is the first of this series, the authors have reviewed the history of the subject, have briefly stated the ordinary rules for plotting magnetic flux in air and in current-carrying copper, have developed additional rules for checking the accuracy of field plots, and have given theoretical methods for mathematically calculating the distribution of field in certain cases commonly encountered in practise.