Results of theoretical and experimental studies of the magnetic characteristics of the electromagnetic system of the prototype Kibble balance is presented. On the basis of the prototype, technical solutions that can be applied in the development of the primary kilogram standard based on the fundamental physical constants are considered. The finite element method was used to design the geometric shapes and dimensions of the system elements in order to obtain a constant value of the conversion coefficient BL . The electromagnetic system was designed and manufactured. On the basis of the State primary standard unit of magnetic losses, magnetic flax density of the constant magnetic field in the range from 0.1 to 2.5 T and magnetic flux in the range from 1∙10-5 to 3∙10-2 Wb GET 198-2017 the installation designed for measuring the topology of the magnetic field in the magnetic system gap was developed. Experimental studies of magnetic flux density distribution in the air gap of the electromagnetic system and outside of it were carried out. The force characteristics of the electromagnetic system were determined. The influence of electric current flowing through the coil in the weighing mode on the change of coil flux linkage was determined. The position of the coil in the weighing mode in which the coefficient of conversion of the magnetic system does not depend on the strength of the electric current in the coil is determined.