A New Design and Analysis of Round-Shaped Transformers Supplying Diode and Controllable Rectifiers

This paper presents a new design of round-shaped transformers applied in diode and controllable rectifiers. Despite conventional three-phase transformers, in round-shaped transformers, voltage is induced on the secondary winding by rotating magnetic field. As a result, in the secondary of this transformer, there can be more than three phases with desired shifts. On the other hand, some rectifier systems may use more bridges supplying from the secondary to improve output dc voltage. However, the rectifier systems produce undesirable current harmonics, especially in controllable systems. This paper discusses how the new design of round-shaped transformers can significantly reduce the harmonic contents of the input current by sinusoidal skewing of the secondary core. The new design is investigated in this paper and its analysis confirms that the harmonics of the input currents can be effectively reduced. Experimental results are also provided to validate the analysis carried out in this paper.