This part of IEC 60974 is applicable to power sources for arc welding and allied processes designed for industrial and professional use, and supplied by a voltage not exceeding 1?000 V, battery supplied or driven by mechanical means. This document specifies safety and performance requirements of welding power sources and plasma cutting systems. This document is not applicable to limited duty arc welding and cutting power sources which are designed mainly for use by laymen and designed in accordance with IEC 60974-6. This document includes requirements for battery-powered welding power sources and battery packs, which are given in Annex O. This document is not applicable to testing of power sources during periodic maintenance or after repair. This fifth edition cancels and replaces the fourth edition published in 2012 and constitutes a technical revision. The significant changes with respect to the previous edition are the following: – improvement of Figure 1 (6.1.1); – modification of Table 3 (6.1.4); – description of energy efficiency measurements in Annex M; – inclusion of battery supplied welding power sources in the scope. Requirements therefore are described in Annex O.