Critical conditions in ferroresonance

The list of references given at the end of the paper by P. H. Odessey and E. Weber on resonance with iron-cored inductances [EE, Trans. Sect., Aug. ´38, p. 444] contains no articles in the English language earlier than 1931. However, this phenomenon was in dependently observed, and described by the writer and C. W. Baker in 1911 in the article “Double Voltages in Circuits having Capacity and Inductance,” in The Electric Journal, 1911, volume 8, page 1102. At that time, as in several later instances, the phenomenon was dangerous and harmful to apparatus on which it occurred. When a small transformer was connected between ground and the terminals of generators, for testing purposes, an unexpectedly high voltage appeared in an erratic manner, which punctured the generator insulation. Sometimes a high voltage and sometimes a low one was obtained, depending on the part of the cycle at which the switch was closed.