INVENTIONS OF NIKOLA TESLA.

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contacts. To avoid this, the motor should be provided with four-teen magnets and seven connected in each circuit, the magnetsin each circuit alternating among themselves. The armatureshould have fourteen closed coils. The action of the motor willnot be quite as perfect as in the case of an even number of poles,but the drawback will not be of a serious nature.

However, the disadvantages resulting from this unsymnaetricalform will be reduced in the same proportion as the number ofthe poles is augmented.

If the generator has, say, n, and the motor % poles, the speedof the motor will be equal to that of the generator multiplied by

n x

The speed of the motor will generally be dependent on thenumber of the poles, but there may be exceptions to this rule.The speed may be modified by the phase of the currents in thecircuit or by the character of the current impulses or by inter-vals between each or between groups of impulses. Some of thepossible cases are indicated in the diagrams, Figs. 18, 19, 20 and21, which are self-explanatory. Fig. 18 represents the condi-tion generally existing, and which secures the best result. Insuch a case, if the typical form of motor illustrated in Fig. 9is employed, one complete wave in each circuit will produce onerevolution of the motor. In Fig. 19 the same result will beeffected by one wave in each circuit, the impulses being succes-sive; in Fig. 20 by four, and in Fig. 21 by eight waves.

By such means any desired speed may be attained, that is, atleast within the limits of practical demands. This system pos-sesses this advantage, besides others, resulting from simplicity.At full loads the motors show an efficiency fully equal to that ofthe continuous current motors. The transformers present anadditional advantage in their capability of operating motors.They are capable of similar modifications in construction, and willfacilitate the introduction of motors and their adaptation to prac-tical demands. Their efficiency should be higher than that ofthe present transformers, and I base my assertion on the fol-lowing :

In a transformer, as constructed at present, we produce thecurrents in the secondary circuit by varying the strength of theprimary or exciting currents. If we admit proportionality withrespect to the iron core the inductive effect exerted upon the