Polyphase transformer arrangements with reduced kVA capacities for harmonic current reduction in rectifier-type utility interface

In this paper polyphase transformer arrangements with reduced kVA capacities are presented for harmonic current reduction in high power diode rectifier-type utility interface systems. Based on the concept of an autotransformer, a 12-pulse rectifier system is realized with a resultant transformer kVA rating of 0.18P_o (pu). In this arrangement the 5, 7, 17, 19, etc. harmonics are absent from the utility input line current. In the second scheme an 18-pulse rectifier is realized with the kVA rating of 0.16P_o (pu) and the 5, 7, 11, 13, etc. harmonics are canceled in the utility line currents. Analytical design equations are presented to facilitate the design of system components. Simulation results verify the proposed concept, and experimental results are provided from a 208 V, 10 kVA 12-pulse rectifier system. The advantage of employing the proposed system for utility interface of rectifier/PWM-inverter motor drive systems is also explained.