Harmonic Analysis of a Mid-Frequency Welder Application for a Metal Working Facility

A proposed Mid-Frequency Welder application for a Metal Working Facility may potentially produce excessive harmonic current and objectionable voltage distortion on the electrical distribution system. A harmonic analysis study commenced to determine the impact of the proposed Mid- Frequency Welder on the existing metal working facility operations, the utility electrical distribution system, especially an adjacent manufacturing facility with extensive electronic controls. The analysis established a baseline for the harmonic distortion produced by the proposed Mid-Frequency Welder and considered the electrical characteristics and expected operating scenarios for the new welder, operating limitations imposed by other plant loads, and operating limitations imposed by the electric utility. The analysis then considered harmonic mitigation methods in the form of line chokes and a passive series-tuned filter. Discussion of additional enhancements included the use of phase-shifting transformers to achieve a 12-pulse or 24-pulse effective system that may entirely eliminate the need for installing filter. This knowledge of the harmonics nature of the Mid- Frequency Welder load and effective harmonic mitigation methods provided valuable data to the welder manufacturer so changes could be made in the design stage to achieve the utility criteria.