Asymmetrical operation analysis of multi-pulse ATRU

Multi-pulse Auto-Transformer Rectifier Unit (ATRU) is the most popular harmonic solution for aircraft application. The characteristic of multi-pulse ATRU under unbalanced input and open-phase condition is analyzed detailed in this paper. By a general model for all kinds of multi-pulse ATRU proposed in this paper, the output characteristics of ATRU under unbalanced input is analyzed with the asymmetric component method. Based on the input voltage decomposing results, it is found that the open-phase operation can be equivalent to single phase operation. Detailed output voltage formulas of ATRU under open-phase are given combining with 12-pulse and 18-pulse ATRU, which are widely used in aviation situation. To ensure the reliability and to improve the power density of ATRU, asymmetrical operation characteristic of transformer is researched. Choosing rule of the maximum flux density is also presented. To verify the analysis, 4kw P type 12-pulse and 18-pulse ATRU are built and gyrator-capacitor simulation model is used to simulate the flux density. Simulation results suggest that unbalanced input results in larger flux density in columns. Experimental results of 12-pulse and 18-pulse ATRU prove the correctness of open-phase analysis.