Discussion on “conditions affecting stability in electric lighting circuits.” New York, January 8, 1909

Chas. P. Steinmetz: The interesting phenomena of instability of electric circuits, discussed by Professor Thomson, have an importance far beyond the arc circuit: the arc circuit is the first and therefore the best known type of unstable circuit due to the work of Professor Thomson and other investigators; but instability occurs frequently also in other electrical and mechanical systems, and the study of the conditions leading to instability thus is one of the most important, subjects of electrical engineering. Thus we find synchronous and induction motors drop out of step, or find such motors starting from rest, but failing to run up to their proper speed; we meet with surging of synchronous apparatus, and find electrical apparatus misbehaving, apparently without reason, at the end of very long transmission lines. In all these phenomena, the same characteristic is the cause of instability, which has been investigated so ably by Professor Thomson in the early days of the arc circuit.