CHAPTER XVII.

Motors With Coinciding Maxima of Magnetic Effect inArmature and Field.

In this form of motor, Mr. Tesla’s object is to design andbuild machines wherein the maxima of the magnetic effects ofthe armature and held will more nearly coincide than in some ofthe types previously under consideration. These types are: First,motors having two or more energizing circuits of the same elec-trical character, and in the operation of which the currents useddiffer primarily in phase; second, motors with a plurality ofenergizing circuits of different electrical character, in or bymeans of which the difference of phase is produced artificially,and, third, motors with a plurality of energizing circuits, thecurrents in one being induced from currents in another. Con-sidering the structural and operative conditions of any one ofthem—as, for example, that first named—the armature which ismounted to rotate in obedience to the co-operative influence oraction of the energizing circuits has coils wound upon it whichare closed upon themselves and in which currents are induced bythe energizing-currents with the object and result of energizingthe armature-core; but under any such conditions as must existin these motors, it is obvious that a certain time must elapsebetween the manifestations of an energizing current impulse inthe field coils, and the corresponding magnetic state or phase inthe armature established by the current induced thereby; conse-quently a given magnetic influence or effect in the field which isthe direct result of a primary current impulse will have becomemore or less weakened or lost before the corresponding effect inthe armature indirectly produced has reached its maximum. Thisis a condition unfavorable to efficient working in certain cases—as,for instance, when the progress of the resultant poles or pointsof maximum attraction is very great, or when a very high num-ber of alternations is employed—for it is apparent that a stronger