IEC 60947-4-2:2011 applies to a.c. semiconductor motor controllers and starters, which may include a series mechanical switching device, intended to be connected to circuits, the rated voltage of which does not exceed 1 000 V a.c. This standard characterizes a.c. semiconductor motor controllers and starters with and without bypass means. This third edition replaces the second edition published in 1999 and its Amendments 1 (2001) and 2 (2006). It is a technical revision. This edition includes the following significant technical changes with respect to the previous edition and its amendments: - updated EMC normative references and associated requirements, - new references to IEC 60947-1, - marking of electronic relays without thermal memory, - marking of tripping time at 0 °C ambient or below, - new test requirements for limits of operation of time-delay overload relays, - new classes of overload current withstand time, - damp heat, salt mist, vibration and shock tests, - short-circuit test in the smallest enclosure, - update of the routine and sampling tests. The contents of the corrigendum of July 2012 have been included in this copy. This publication is to be read in conjunction with IEC 60947-1:2007.