Negative Resistance Effects in Saturable Reactor Circuits

Sustained oscillations exhibiting many of the properties of free oscillations are found in saturable reactor circuits under appropriate conditions. The frequencies of such oscillations are classified in relation to that of the driving source as 1. Incommensurable. 2. Subharmonic, and multiples thereof. 3. Harmonic. General properties of the oscillations classified are elucidated by reference to an analysis of R. V. L. Hartley's, dating back to 1917. In part I a comparatively simple form of analysis is used to demonstrate the development of negative resistance by what is essentially a modulation process. Applications are then made to the three classes of oscillations listed. Some of the simplifying assumptions of part I are removed in part II to approximate practical conditions more closey for the evaluation of a specific product, the third subharmonic. Quantities evaluated over wide ranges of the variables involved include the impedance of the non-linear coil to the subharmonic, the subharmonic amplitude, its stability, and the conditions required for starting and maintaining the oscillation. Experimental data are found in general agreement with the results of computation.