New 24-pulse diode rectifier systems for utility interface of high-power AC motor drives

This paper proposes two new passive 24-pulse diode rectifier systems for utility interface of pulsewidth modulated (PWM) AC motor drives. The first approach employs an extended delta transformer arrangement, which results in near equal leakage inductance in series with each diode rectifier bridge. This promotes equal current sharing and improved performance. A specially tapped interphase transformer is then introduced with two additional diodes to extend the conventional 12-pulse operation to 24-pulse operation from the input current point of view. The proposed system exhibits clean power characteristics with fifth, seventh, eleventh, thirteenth, seventeenth, and nineteenth harmonics eliminated from the utility line currents. The second scheme is a reduced voltampere approach employing autotransformers to obtain 24-pulse operation. The voltampere rating of the polyphase transformer in the second scheme is 0.23P₀ (PU). Detailed analysis and simulations verify the proposed concept, and experimental results from a 208-V 10-kVA rectifier system are provided