On the Efficiency and Reliability of High-Current Rectifiers

Industrial electrolytic rectifiers work with high currents (in the order of kilo Amps) and very low dc voltage levels (few hundred Volts). The preferred industrial solutions for this type of application are thyristor-based double-bridge and four-star multi-pulse rectifiers. A number of alternative more advanced rectifiers have been recently proposed presenting improved electrical properties, such as reduced harmonic distortion and reduced reactive power consumption. The various tradeoffs existent between these topologies have been evaluated only partially. This paper presents a full evaluation method based on standards. It should become a valuable tool for the plant design engineer offering quantitative figures to support the electrical project. The proposed method is based on the reliability, electrical performance, efficiency and required equipment investment for these rectifiers. The IEEE standards 493-1997 and IEEE C57.18.10 for reliability and efficiency are the basis of this method, being used specifically to configure the evaluation platform. Complete results are presented for the conventional double-bridge and four-star rectifiers, and for, "late harvest" rectifier topologies including the chopper-rectifier, the sequential rectifier, and the filterless rectifier. From these, it is concluded that the modular multi-cell technology used in the chopper high-current rectifier is capable to challenge thyristor-based industrial solutions