The Theory and Design of Radio-Telegraphic Transformers

Starting with the general solution of the differential equation of the circuit and a steady sparking state, expressions for input, output, currents, and condenser charge are calculated by means of the boundary conditions of the interval. The boundary conditions are continuity of currents at sparking and a residual condenser charge experimentally determined. Calculated current and voltage waves for a special case are compared with an oscillogram taken for the same transformer constants. A number of curves illustrating the quantities studied (and also curves facilitating their computation) are given; and, on comparison, are found to agree closely with oscillograms taken during actual operation. On the basis of the derived theory, a complete set of transformer measurements are explained, and numerical illustrations given. The effect of harmonic components in the e.m.f., and the avoidance of their effects are explained, together with the effect of the wave form of the e.m.f. In connection with the experimental verification of the theory, there are described the necessary measuring apparatus, including the oscillographs. The design of the transformer to meet any desired requirements is then treated in detail from the theoretical and practical standpoints. The use of air core power transformers at frequencies of 500 cycles and over is considered and found to be feasible. An interleaved set of coils of "Maxwellian" cross section is recommended for the "sandwiched" primary and secondary. An actual satisfactory transformer of this type for 2 K. W. is described.