Generally, the rectifier bridge has a large enough inductive load, so there is no current interruption in the rectifier bridge. When the general rectifier bridge is used, it is often connected with a smoothing reactor at its load end, so its load can be regarded as a constant current source. Several groups of three-phase rectifier bridges are connected with each other, so that the harmonics generated by the rectifier bridge circuit cancel each other. According to the type of rectifier transformer, it can be divided into traditional multi-pulse transformer rectifier and self-coupling multi-pulse transformer rectifier. The traditional multi-pulse transformer rectifier uses isolation transformer to isolate the input voltage from the output voltage, but the rectifier transformer has large equivalent capacity and huge volume. Because the general rectifier bridge is often connected with a smoothing reactor at its load end, its load can be regarded as a constant current source. In addition, according to the EMI measurement standard, in order to reduce the influence of the grid impedance on the measurement results, it is necessary to connect the linear impedance stabilization network (LISN) at the grid input of the rectifier bridge.