STUDY OF THE REGULARITY CONDITIONS AT SERIAL CONNECTION OF TWO-PORTS

Abstract

The possibility of preserving the regularity condition for composite two-ports formed by serial connection of the original ones is studied. Numerous textbooks, reference books, collections of problems on the theoretical foundations of electrical engineering provide a rule for determining generalized parameters at the series connection of two-ports by adding the matrices of coefficients Z' and Z'' of the original ones. These sources note that this rule is true only in cases when the regularity condition is met, i.e. pairwise equality of currents at the input and output of each of the two-ports is maintained in any mode of operation of the electrical circuit. When two-ports are connected in series, a new electrical circuit is obtained in which maintaining pairwise equality of currents in two pairs of selected branches can only be a private mode. That is why, it is doubtful that when connecting two-ports in series, the application of the known rule will take place. All possible options for the serial connection of two different two-ports presented by an equivalent T-shaped circuit are considered. To solve the problem, the loop current method is used and a condition is determined under which the pairwise equality of currents at the input and output of each of the two-ports in the load mode is maintained. As a result, it turns out that when connecting two-ports in series, the condition of regularity of the connection is not satisfied. In two of considered cases, the two-ports are converted, and in the third case, the composite two-port is converted into one pass-through two-port. This statement is also confirmed by determining the Z parameters of a composite two-ports by adding the matrices of coefficients Z' and Z'' of the original ones, which is satisfied only in the third of the considered variants.