The basic theory column we started in the Digital Innovations Center’s newsletter is starting to get a little meatier as we progress toward combining those basics. This month’s TranspowerNZ video is focused on the 6-pulse bridge also known as the Graetz converter bridge. This device is a three-phase device. It is used in both the inverter and the rectifier and for the first time we are introduced to firing angle alpha (ά).
The 6-pulse bridge has a pulse number of 6 and can be thought of as a 6 phase, half wave circuit. It was used in early converter stations before being replaced by the 12-pulse rectifier, which we’ll go into in more detail in another month’s theory column. The 6-pulse rectifier had problems with high harmonic distortion for both the AC and DC sides of the converter.