Discussion on “air gap flux distribution in direct-current machines” (Moore), Portland, Ore., April 18, 1912. (see proceedings for March, 1912)

H. Weichsel: The method used by Mr. Moore for investigating the actual flux distribution in a direct-current machine consists in determining by means of an oscillograph the wave shape of the alternating e.m.f. generated in an armature coil spanning 1 8 0 electrical degrees. The assumption is then made that the field distribution is similar to the wave shape of the generated e.m.f., providing we consider that the base line of the half wave is equal to the pole pitch of the machine. This assumption leads to correct results if the field distribution is absolutely constant and does not change with time. If, however, the field distribution or the field strength changes with time this method must lead to incorrect results.