[en] A frequency dependence of hysteresis losses in superconducting single filament wires NT-50 in a transverse and a longitudinal magnetic fields is studied. Measurements are carried out by the calorimetric method at the gas-holder type installation with approximately 1 mW sensitivity threshold. Existence of a logarithmic dependence of hysteresis losses on the rate of magnetic field variation is experimentally verified. It is shown that the dependence is due to the exponential function of V-A characteristics of technical superconductors. Measurements of the rate dependence of losses can be used as a method for indirect determination of the build-up parameter for circular currents in superconducting wires