Modeling and Simulation of 6-Pulse and 12-Pulse Rectifiers under Balanced and Unbalanced Conditions with Impacts to Input Current Harmonics

Abstract

This paper discusses the impact of using 6-pulse and 12-pulse rectifier circuit commonly found in Adjustable Speed Drives. The 12-pulse topology is known to be more expensive, but produce the least input current harmonics. However, the latter statement is completely true under balanced line conditions. In practice, the lines are inherently unbalanced. Hence, the question of whether the 12-pulse rectifier will indeed perform better in terms of the harmonics injected to the line is still under on-going discussions. This paper presents the modeling and simulation of both rectifier topologies to compare their input current harmonics. The rectifiers are modeled using OrCAD Pspice and several common cases of line conditions will be simulated to compare their harmonic levels. Results of the simulations pertaining to their Total Harmonic Distortions for each case will be explored.