The study of the active multipoles, whose individual circuits are connected in the form of a star, was conducted. The aim of the research is to determine the conditions for obtaining maximum power under the load. The solution is found using the principle of a superposition and an analytical search for an extremum in an active DC three-pole. It is ensured that the necessary condition is the equivalence of the active resistance of the source and the load in each branch, regardless of the electromotive force of the source. It is based on a special symmetry of partial differential equations – in each equation the resistance of the branch of the sources is summed up with the resistance of the same branch of the load. The scientific novelty of this work consists in the analytically accurate substantiation of the condition for achieving the maximum power for an n-phase AC network with the isolated neutrals – full resistances in each branch of the load must be equivalent to conjugate complex resistances of a source. A new method for the experimental determination of internal resistances of both of a three-phase and n-phase source of electrical energy is proposed. It is based on the selection of conjugated complex resistances of the load and the source. The procedure consists of two stages: ensuring the voltage resonance in each phase of a multipole and iterative selection of the resistance of the load in each phase to obtain the maximum power. The MULTISIM model can be used in virtual laboratory works for the study of the electrical engineers.