Electromagnetic interference considerations for automated welding cells

Abstract

The paper concerns a systematic approach to transient-noise suppression which is essential for the development of automated TIG (Tungsten-Inert-Gas) welding systems for industry. The principal source of noise is the initiation of the arc both at the start of and during the welding process. Arc initiation is attained by a number of techniques involving high voltages and high frequencies. The solution of two case studies involving DC and AC (mains) TIG welding have been given in detail. The worst case of interference occurs for AC (mains) TIG welding because it is necessary to reignite the arc constantly when the arc voltage crosses zero level. This occurs at a frequency of 100 Hz. The interference noise has been suppressed by a combination of techniques involving filtering, grounding, isolation and shielding. Fibre-optic links and optoisolators are an essential part of the solution. The research has resulted in the production of robust TIG welding systems used by industry.