Specifies requirements for the design, performance and rating of - (a) arc welding machines with transformers for alternating current metal-arc welding; and (b) arc welding machines with transformer-rectifier units for direct current, or alternating curren/direct current, metal-arc welding. It applies to welding machines having an output of the drooping characteristic type (substantially constant current) and machines of the flat characteristic type (substantially constant voltage), but does not necessarily cover the requirements for use in the gas tungsten arc (GTA) , gas metal arc (GMA), or other specialized welding processes.