Solution of Topical Issues in Theory of Transformers

Abstract

In the article, the authors summarized their experience in solving some controversial issues in the theory of transformers, and briefly outlined the essence of their developments. For power transformers of the TM series, the presence of an excess of the active resistance of the primary winding relative to the reduced active re-sistance of the secondary winding was established. The obtained correction factors, taking into account the electrical skin effect in the windings and their heating, can be used to calculate short-circuit currents and heat distribution in other types of transformers. An expression is given that makes it possible to correct the transfor-mation ratio of one of the transformers connected to parallel operation in such a way that it becomes possible to fully load both devices, despite their different short-circuit voltages. Expressions are presented that make it possible to reveal the ratio of hysteresis and eddy-current losses in the magnetic circuit of a particular trans-former, as well as the exponent with which the losses in the magnetic circuit depend on the frequency of mag-netization reversal. A method is proposed for determining the three components of losses in a magnetic circuit, based on an idle experiment at three frequencies. A method is described for determining the thickness of sheets of a magnetic circuit, at which the total losses in it are minimal, and a method for determining the heating time constant of dry transformers is presented, which makes it possible to accelerate their thermal tests.