Standard for Low-Voltage Switchgear and Controlgear - Part 4-2: Contactors and Motor-Starters - AC Semiconductor Motor Controllers and Starters
UL 60947-4-2
1 Scope and object
This standard applies to 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 controllers and starters with and without bypass means.Controllers and starters dealt with in this standard are not normally designed to interrupt short-circuit currents. Therefore, suitable short-circuit protection (see 8.2.5) should form part of the installation, but not necessarily of the controller or starter.In this context, this standard gives requirements for controllers and starters associated with separate short-circuit protective devices.This standard does not apply to:

• continuous operation of a.c. motors at motor speeds other than the normal speed;
• semiconductor equipment, including semiconductor contactors (see 2.2.13 of IEC 60947-1) controlling non-motor loads;
• electronic a.c. power controllers covered by IEC 60146.

Contactors, overload relays and control circuit devices used in controllers and starters should comply with the requirements of their relevant product standard. Where mechanical switching devices are used, they should meet the requirements of their own IEC product standard, and the additional requirements of this standard.The object of this standard is to state as follows:

• the characteristics of controllers and starters and associated equipment;
• the conditions with which controllers and starters shall comply with reference to:
• their operation and behaviour;
• their dielectric properties;
• the degrees of protection provided by their enclosures where applicable;
• their construction;
• the tests intended for confirming that these conditions have been met, and the methods to be adopted for these tests;
• the information to be given with the equipment, or in the manufacturer's literature.