Tesla Suggests a Method for Rectifying Alternating Currents

Our esteemed contemporary the Electrical World devotes an article to describing the methods suggested by M. Nikola Tesla for rectifying alternating currents. We must confess to a certain amount of scepticism as to the availability of these methods for large currents. On another page of the same journal M. A. Gaillard describes an apparatus for effecting the same purpose, which has a close resemblance to a device described by Mr. Lane Fox some years ago intended to do this. It is obvious, however, that anything like mercury cups or spring contacts, however effective for currents of a few amperes in magnitude, will fail when larger currents are used. The commutation of alternating currents by a motionless commutator capable of dealing with currents of all magnitudes and various frequencies is a problem which may well tax the highest inventive skill, but these devices of M. Tesla do not seem very perfect solutions of the question. The method adopted of splitting the alternating current through two coils having magnetically saturated cores is very ingenious, depending as it does on the fact that the self-induction of the coil varies with the permeability of the core, and this varies with the induction through the core.