Nikola Tesla Books
THE HIGH POTENTIAL TRANSFORMER 21 the spark, the potential instantly drops to so low a value that the arc dies out of its own accord; indeed, it is doubtful if any appreciable arc forms at all. The principles of the magnetic leakage transformer are shown in Fig. 6, 7 and 8. In Fig. 6, the primary and secondary are seen to be mounted upon separate legs of the rectangular iron core. This loosens the coupling to such an extent that magnetic leakage is set up in the space between the windings and around the outside of the core as shown by the lines in the drawing. This leakage diverts a portion of the total flux from its path through the cores inside the windings and, when the abnormal load comes on the secondary, the potential suffers a tremendous drop as the regulation is intentionally poor. In Fig. 7, the primary and secondary are still farther separated by being placed upon the short legs of the core instead of the long ones as shown in the preceding figure. This is carrying the point still farther. In Fig. 8, we have the true Type E instrument in which a tongue of iron projects from one leg of the core, between the windings, and nearly makes contact with the opposite leg. This introLINE IMPEDANCE COIL Fig. 5.-Transformer with closely coupled primary and secondary and the impedance coil in series with primary to prevent arcing at spark gap
