Nikola Tesla - Free-Energy Devices

114 INVENTIONS OF NIKOLA TESLA.been done, Mr. Tesla protectsin a measure the secondary fromthe inductive action or effect of the primary by surroundingeither the primary or the secondary with a comparatively thinmagnetic shield or screen. Under these modified conditions,as long as the primary current has a small value, the shieldprotects the secondary; but as soon as the primary currenthas reached a certain strength, which is arbitrarily determined,the protecting magnetic shield becomes saturated and the inductiveaction upon the secondary begins.It results, therefore, thatthe secondary current begins to How at a certain fraction of aperiod later than it would without the interposed shield, andsince this retardation may be obtained without necessarily retardingthe primary current also, an additional lag is secured, andthe time interval between the maximum or minimum periods ofthe primary and secondary currents is increased. Such a trans-FIG. 95.former may, by properly proportioning its several elements anddetermining the proper relations between the primary andsecondary windings, the thickness of the magnetic shield, andother conditions, be constructed to yield a constant current at allloads.Fig. 95 is a cross-section of a transformer embodyingthis improvement.Fig. 96 is a similar view of a modified form oftransformer, showing diagrammatically the manner of using thesame.A A is the main core of the transformer, composed of a ringof soft annealed and insulated or oxidized iron wire. Upon thiscore is wound the secondary circuit or coil B B. This latter isthen covered with a layer or layers of annealed and insulatediron wires c c, wound in a direction at right angles to the secondary