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 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 reactor 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 5th, 7th, 11th, 13th, 17th and 19th harmonics eliminated from the utility line currents. The second scheme is a reduced kVA approach employing autotransformers to obtain 24-pulse operation. The kVA rating of the polyphase transformer in the second scheme is 0.18 P_o (PU). Detailed analysis and simulations verify the proposed concept and experimental results from a 208 V, 10 kVA rectifier system are provided