Subharmonics in iron-cored reactor oscillatory circuits

This report gives a careful study of subharmonic sustained oscillations found in iron-cored reactor oscillatory circuits. The analysis is based on the power balance principle, giving satisfactory explanation and understanding of the idea of frequency conversion. The analysis is valid for both the harmonic and subharmonic cases. The ranges of synchronization, the methods of starting, and the conditions of stability of these oscillations are given. Numerical examples for the third subharmonic oscillations are presented. Just outside the locking range, the amplitude and phase of the subharmonic oscillations are no longer constant, but variable; the oscillations are defined as ¿pulled oscillations.¿ A theoretical analysis for determining the instantaneous phase angle is given. An experimental investigation to test the validity of the theoretical analysis is carried out. The experimental work includes steady and transient conditions, a harmonic source of voltage being applied. The ranges of the supply voltage switching angles required for starting sustained oscillations for different circuit parameters are experimentally obtained. An initial charging of the condenser or an instantaneous application of d-c flux improves the starting conditions.