Voltage Distortion on an Electrical Distribution System

This article described a harmonic analysis study that determined that the proposed midfrequency welder would produce unacceptable voltage distortion on the utility electrical distribution system, especially an adjacent manufacturing facility with extensive electronic controls as well as on the house load associated with the midfrequency welder. The voltage distortion was characterized by significant notching and false zero crossings, both of which could affect electronic control circuits, while the latter could affect timing circuits such as the welder. The article then showed that the installation of line chokes in combination with a fifth harmonic single-tuned filter improves voltage distortion to within acceptable limits. Finally, the article explained that additional enhancements including the use of phase-shifting transformers to achieve a 12pulse or 24-¿ulse effective system may entirely eliminate the need for installing a filter. This knowledge of the harmonics nature of the midfrequency welder load and effective harmonic mitigation methods provided valuable data to the welder manufacturer so that changes could be made in the design stage to achieve the utility criteria.