Equivalent Circuit and Vector Diagram of an Autotransformer with Mapping of Magnetic Fluxes

A universal equivalent circuit of an autotransformer with explicit mapping of its main characteristic—transporting energy by two parallel paths (electrically and electromagnetically)—is presented. At the same time, a diagram displays the magnetic fluxes in the window sections and in separate sections of the magnetic circuit, as well as when the steel is saturated between it and the tank. A similar completeness of representation of the power and magnetic fluxes is provided by the vector diagram of autotransformer operating mode. With its help, a high degree of clarity was achieved when explaining overexcitation of individual parts of a magnetic circuit in a short-circuited autotransformer and when deriving formulas for determining super- and antisupercurrents in comparison with idle fluxes in this mode. The presented equivalent circuit is suitable for step-up and step-down autotransformers and is applicable to the study the steady-state and transient processes.