IEC 60974-4:2010 specifies test procedures for periodic inspection and, after repair, to ensure electrical safety. These test procedures are also applicable for maintenance. This standard is applicable to power sources for arc welding and allied processes designed in accordance with IEC 60974-1 or IEC 60974-6. Stand-alone ancillary equipment designed in accordance with other part of IEC 60974 may be tested in accordance with relevant requirement of this part of IEC 60974. This second edition cancels and replaces the first edition published in 2006. It constitutes a technical revision. The main significant technical changes with respect to the previous edition are the following: – title is amended; – scope is extended to equipment designed in accordance with IEC 60974-6; – complementary instructions from the manufacturer shall be followed; – qualification of test personnel is clarified (see 4.1); – plasma cutting power sources are excluded from no-load voltage test (see 5.6); – voltage reducing device functional test is simplified (see 6.3); – supply voltage is recorded in test report (see 7.1).