A rotating magnetic field approach to a low distortion poly-phase power rectifier

The rotating magnetic field generated by a balanced three phase AC system of currents is employed to excite a polyphase secondary which is subsequently rectified. The use of the rotating magnetic field structure has distinct advantages for isolating the input AC system from the rectified DC system and, therefore, substantially reducing the current distortion present to a much lower level than in conventional rectifier circuits. This effect is achievable because the three phase currents generating the rotating magnetic field present a continuous balanced load to the input three phase AC system. Several models of this concept have been constructed. This paper presents the results obtained from the models and from a 5 kW operational system used to rectify three phase power for a high rate battery charger. The DC output ripple characteristics and reduced input harmonic line current distortion are discussed in comparison with standard transformer circuits with the same number of switching pulses.