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. This publication is to be read in conjunction with IEC 60947-1:2007.