Richardson's handbook of projection (1927)

5% HANDBOOK OF PROJECTION FOR The Transformer THE transformer cannot be used on direct current. It is a device made entirely for use with A. C. Its purpose is to change alternating current of any given cycle (frequency) and voltage and amperage to an alternating current of the same cycle, but of different voltage and amperage. The transformer assembly consists of four separate elements, viz.: a laminated core of iron, a primary coil, a secondary coil and a protecting casing or covering. In addition to this there may be other elements, such as an adjusting switch by means of which the amperage delivery of the secondary coil may be varied. In Fig. 197 we have diagrammatic representation of the simplest form of transformer. The primary coil is wound around one "leg," or side of a laminated iron core, from which it is completely insulated. The secondary coil is wound around the other leg or side of the core, from which it also is completely insulated. In Fig. 197 it is only intended to convey a general idea of the relation of coils and core. In actual practice coils are located as close together as they can be In some forms of construction one coil is inside the p */M*> ?y StVCM&tfX Figure 197. the gotten other. ELECTRICAL ACTION.— The electrical action of a transformer is primarily based on the fact that if a wire be charged with alternating electro motive force it will be surrounded by a magnetic field, as illustrated in Fig. 198, in which A is a wire charged with A. C, B another wire having no mechanical connection with wire A, and the circles lines of magnetic force. Under the conditions shown, although wire B has no metallic connection with wire A, and is electrically insulated therefrom, an alternating Current electro motive force will