Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 68)

U s
U
s
Fig. 2.4-13
Principle of mirror contacts: the normally open auxiliary contact remains open when the contactor is de-
energized and a main contact has welded.
A power contactor can have several auxiliary mirror contacts. In large contactors it may be
necessary to connect two mirror contacts in series, one of which is mounted on the left and the
other on the right side. Thus even if the contact armature is in an inclined position – for example
if an outside contact has welded – safe feedback is ensured.
Like mechanically linked contacts, mirror contacts must be marked directly on the device, in the
documentation or in both locations.
Fig. 2.4-14
Symbol for marking mirror contacts
2.4.7 Installations in hazardous atmospheres
2.4.7.1 History, guidelines and regulations
The Directive 94/9/EC (ATEX 05) regulates the requirements for explosion protection in the
European Union. It deals with the properties of explosion-protected devices, protective systems
and components for free trade in the internal market of the EU and stipulates that the use of
such devices in member states may not be prohibited, hindered or restricted.
The Directive is structured in accordance with the so-called “New Approach”. A key feature is
renouncing from strict normative regulations; instead the requirements on the products are
comprehensively defined directly in the directive (Appendix II: Essential health and safety
requirements relating to the design and construction of equipment and protective systems
intended for use in potentially explosive athmospheres). This is done in a general form, so that
reference to suitable standards is normally preferable.
While placing on the market of explosion-protected devices (protective systems, components) is
uniformly regulated by Directive 94/9/EC, the safe operation of these devices is ultimately
regulated under national ordinances. The Directive 1999/92/EC, also known as the Safety at
Work Directive, defines minimum requirements below which the requirements of the national
regulations may not fall.
LVSAM-WP001A-EN-P - April 2009 2-40