Series-connected magnetic amplifier with inductive loading

THE circuit to be considered in this paper is the series-connected magnetic amplifier with resistance and linear inductance in either the load circuit or the control circuit, or in both circuits simultaneously, Figure 1. This circuit with modifications has been analyzed by many authors, a few of whom are mentioned in references 1 to 9. In almost all the analyses simplifying assumptions have been made concerning the magnitude of some of the circuit parameters, very little work having been done on circuits in which La and Ld are not zero. It is the object of this paper to analyze and discuss the changes in current wave shapes produced by variation of the circuit parameters Ra, Rd, La, and Ld. In order to understand these changes the circuit is analyzed mathematically. The magnetization constraint of the cores is approximated by three linear segments as shown in Figure 2. The procedure, following a method first used by A. Boyajian,10 is to obtain solutions for the circuit currents and core fluxes which apply only when the cores are operating on specified linear segments of their respective magnetization curves. When the cores are operating on such a pair of segments the equations of the system become linear, and consequently are solved easily. It is necessary then only to match final and initial conditions at the time of transition from one segment to the next. Equations are thus derived which permit calculation of the instantaneous values of the circuit currents and core fluxes in transient and steady-state conditions. The equations are verified by quantitatively comparing calculated instantaneous values of the current wave shapes with the instantaneous values obtained experimentally. They then are used to explain the changes of wave shape which occur when any of the circuit parameters are changed.