CHAPTER XXI.

Motor with a Condenser in the Armature Circuit.

We now come to a new class of motors in winch resort is hadto condensers for the purpose of developing the required differ-ence of phase and neutralizing the effects of self-induction. Mr.Tesla early began to apply the condenser to alternating appara-tus, in just how many ways can only he learned from a perusalof other portions of this volume, especially those dealing withhis high frequency work.

Certain laws govern the action or effects produced by a con-denser when connected to an electric circuit through which analternating or in general an undulating current is made to pass.Some of the most important of such effects are as follows : First,if the terminals or plates of a condenser be connected with twopoints of a circuit, the potentials of which are made to rise andfall in rapid succession, the condenser allows the passage, or morestrictly speaking, the transference of a current, although itsplates or armatures may he so carefully insulated as to preventalmost completely the passage of a current of unvarying strengthor direction and of moderate electromotive force. Second, if acircuit, the terminals of which are connected with the plates ofthe condenser, possess a certain self-induction, the condenser willovercome or counteract to a greater or less degree, dependentupon well-understood conditions, the effects of such self-induc-tion. Third, if two points of a closed or complete circuitthrough which a rapidly rising and falling current flows heshunted or bridged by a condenser, a variation in the strength ofthe currents in the branches and also a difference of phase of thecurrents therein is produced. These effects Mr. Tesla has utilizedand applied in a variety of ways in the construction and operationof his motors, such as by producing a difference in phase in thetwo energizing circuits of an alternating current motor by con-necting the two circuits in derivation and connecting up a con-denser in series in one of the circuits. A further development,