Calculation of No-load Currents Using Hysteresis Loop

An improved approach has been applied to increase the efficiency of field simulation of the research no- load mode by setting the conditions of symmetry of the magnetic field on a plane with the axes of the limbs of the magnetic system. Harmonic composition of the phase no-load currents are determined. The features of non-sinusoidal changes in time of momentary values of no-load currents are determined. It is shown that the amplitude of the main harmonic decreases for the positive phase-sequence by 5.08% of the amplitude of the transformer no-load current and increases to 27.91% for the negative phase-sequence. The prevailing influence of the odd higher harmonic components of the no-load phase currents are established. The use of a compensating winding system, which is connected to the adjusting windings, reduces the effective value of the no-load current of the negative phase-sequence; approximates the effective value of the first harmonic of the no-load current; reduce the deviation of the phase shift angles compared to the symmetric idle mode up to 2%.