In the article, the magnetic circuit of a differential type angular displacement transformer converter with a variable active area of the movable core is considered as a magnetic circuit with distributed parameters in which the width of the movable ferromagnetic core is a function of the angular displacement of the converter. Studies have established that when the magnetic resistance of the steel part of the magnetic circuit is not taken into account, the working magnetic flux is a linear function, and when taking into account the distributed nature of the magnetic resistance of the steel part of the magnetic circuit and the magnetic capacity of the air gaps, it is a nonlinear function of the angular displacement of the converter and the degree of this nonlinearity is greater, the lower the value of the relative magnetic permeability of the material of the steel part of the magnetic circuit of the converter.